The Fiber Laser Learning Lab Series with Russ Sadler
In this Series, Lotus Laser have lent Russ a MOPA 20 watt fiber laser to “play with”. Although Russ has a moderate understanding of laser technology (his words) and how constant power glass tube systems work, pulsing fiber laser marking machines are shrouded in a deeper mystery than the glass tube machines.
They have been designed for high speed marking and the technology has been well tried and proven. There are limited “tricks” that the pulsing laser technology can perform. You enter predefined parameters for each marking “trick” you wish the machine to deliver , then stand back in amazement. Most correspondents tell Russ that they have bought their machine direct from China and received a machine and EZCAD software, preloaded with a few default parameters. No other instructions beyond the EZCAD manual are forthcoming.

Russ states “I am neither a teacher or expert in this field so you join me in my learning adventure with the warning that I have a simple but inquisitive mind and will probably make mistakes on my way to discovering the truth. I WILL oversimplify and maybe distort the scientific detail in my quest to build a simple picture of why and how this technology works. I am not trying to reverse engineer anything, just to break through the seemingly impenetrable ‘techno cotton wool’ that surrounds this amazing piece of science.”
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Transcript for Introduction to Fiber Laser Marking
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hi no my name’s Russ and I’d like to
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welcome you to this new series where I’m
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going to be exploring fiber laser
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marking machines well this one in
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particular we’ll talk about that in a
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second I think you could see I’m old I’m
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gray
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I’m Oakley I’m fat I’m also an ex
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engineer I’ve been involved in all
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aspects of engineering during my career
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and at one stage I own some co2 metal
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cutting laser machines so I thought I
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knew everything there was to know about
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nicer cutting until I got one of these
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Chinese machines and then all of a
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sudden I realized that I knew a lot
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about the machine and the way it’s
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rylynn the way it was maintained but
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nothing about the actual laser
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technology itself and so for the past
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four years I’ve been teaching myself
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very slowly but then again you’d expect
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that of somebody of my age wouldn’t you
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how these machines work what the
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technology is that makes them work
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successfully and I’ve been delving into
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some really dark corners that most
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people don’t bother to dig into these
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are hobby machines and lots of hobbyists
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just use them for small businesses or to
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play with yeah I play with mine as well
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but I specifically I’m an inquisitive
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person and I’d like to know how and why
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things work okay so I’m sitting here
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with my arm on a very nice
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fiber-optic laser marking machine why
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well we’re just about to start another
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learning journey into a different world
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of laces now the learning journey is
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mine maybe it’s yours as well but
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specifically I am the one that’s
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learning so always bear that in mind
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when you look at this when you watch
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these videos I can easily make mistakes
Transcript for Introduction to Fiber Laser Marking (Cont…)
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because there aren’t many people out
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there that can tell me a great deal
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about these machines they can tell me a
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lot about what they do and how they do
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it and the parameters that you need to
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set but that’s not what I’m after I want
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to dig into the dark corners and find
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out what this machine is really capable
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of let’s just give you a quick tour
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around the machine and then we’ll give
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you a quick demonstration first of all
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let’s take a look at the work area this
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is it no XY slides as you can see just a
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nice clean open work area with T slides
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in it so you can bolt down rotary unit
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if you want to this is a high-volume
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production marking machine now this is a
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product where the red anodized aluminium
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has been removed with a fiber laser you
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know every property three seconds go be
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another product offered in front of the
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laser this product is not flat the great
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advantage of this machine is it can mark
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non flat products because here’s the
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lens the lens is about 12 inches above
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the work surface and that means it’s an
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incredibly long focal length lens with
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quite a wide focal range on it so it can
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easily work over a curved surface like
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this now we can never get up inside the
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head to see what’s going on behind the
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lens so here’s the lens and that behind
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the lens we’ve got two mirrors one for x
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axis and one for y axis which is
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steering the beam that’s coming out of
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the laser machine now these are operated
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by two motors now these mirrors have got
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very very low mass and they can move
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incredibly quickly so the scanning speed
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of this machine I don’t know exactly
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what it is but I think it’s somewhere in
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the region about two meters a second
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which is incredibly fast but it’s all
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because of the low mass of these mirrors
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so that’s what’s hidden away up behind
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that lens there which I can’t get to
Transcript for Introduction to Fiber Laser Marking (Cont…)
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can’t just can’t do anything about it is
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what it is so the only thing that we can
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do to control this machine that’s assets
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and parameters that’s all I’ve got to
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play with now whether there are ways of
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defeating this software and going
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outside those limits I don’t know as yet
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I’ve got to investigate that but hey for
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the time being I think we’ll stay within
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the rules now at the back of the machine
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we’ve got a an extraction system and
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that’s what this cone is it’s an
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extraction system for pulling the fumes
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away from the engraving area now up in
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the machine there we’ve got a red box
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which is where all the clever
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fiber-optic work is being done or the
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electronic controls and here we’ve got
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the beam expanding system which takes
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the fiber-optic and opens the beam up
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ready to be processed by this lens here
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we’ve got a simple control panel at the
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front here with the emergency stop
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button and we’ve got a couple of key
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switches one which turns the machine on
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and off sorry this one turns the machine
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on and off and this one switches the
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interlocks on and off at the moment the
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interlock is on which means as soon as I
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press the start button this cover will
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come down and it will protect my eyes I
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can choose to operate it with the cover
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open like this which from time to time I
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should certainly be doing for you guys
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to show you what’s going on these were
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perfectly okay for protecting my eyes
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when I was working with the co2 laser
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but here we are on the fiber laser which
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is a different frequency of light I need
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to be a bit more careful with my eyes
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and when the guard is open I’m going to
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have to assume a Hollywood film star
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persona here we are on the co2 laser
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machine and we got to do a little teeny
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weeny bit of engraving and a speed and a
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power which is a close approximation to
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what we should be able to do on the
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now this is black anodized aluminium and
Transcript for Introduction to Fiber Laser Marking (Cont…)
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what we’re doing here we’re removing the
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black dye from the aluminium and leaving
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the aluminium oxide surface behind which
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is white okay now without changing
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anything I’m going to put a piece of
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glass over that then we’re going to
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repeat the same thing again so everybody
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with the co2 laser will recognize what
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I’ve done there I’ve been graved the
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surface of the glass and nothing no
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power at all has come through because
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the power has been a hundred percent
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absorbed by the glass okay so here we
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are on the fiber laser now I’m operating
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this machine at the moment with the
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guard open but I’ve got my film star
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goggles on and there’s a engraving that
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took place on the surface of the glass
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when we had it
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just there okay we’re now going to
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perform exactly the same trick on the
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favor
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so if I catch in the light right you can
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see that there is a mark on the back of
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the glass there it’s not on the front of
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the glass it’s a very very faint mark on
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the back of the glass there is a small
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amount of damage there to indicate it
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may well have done a little bit of
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engraving but it’s very very faint
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basically the glass has been completely
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transparent to infrared light at 1
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micron wavelength whereas at 10 point 6
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micron wavelengths the glass is
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completely opaque and the damage is
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taking place on the top surface here the
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energy is transferred right through the
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glass and it’s damaged the material
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underneath as though the glass wasn’t
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there look this was without the glass
Transcript for Introduction to Fiber Laser Marking (Cont…)
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and this was with the glass now after
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that little demonstration you may well
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now begin to understand that all lasers
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are not the same so I think we’ll start
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by explaining how a constant power co2
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laser works and then we’ll migrate from
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that into the fiber laser technology
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which is still a laser and the
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technology of lasing will still be the
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same and that’s what I think we must
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tackle before we even attempt to do
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anything with this machine I want to
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understand what it is that this machine
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is and can do I don’t even know what
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this machine is at the moment so how can
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I think about what it can do yet I could
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follow lots of YouTube clips and I could
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see lots of little parameter settings to
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make the machine do its tricks but
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that’s not what I’m about I want to
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understand why and how each one of those
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tricks can be done and how and why it
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takes place so
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this is not going to be an easy journey
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it’s going to be quite a technical
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journey but I am NOT a technical person
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I’m certainly not a physicist and I’m
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certainly not a chemist so anything that
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I described to you will be a very
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distilled and simplified version of the
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truth now before I get any further into
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this video I must just say a big thank
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you to the guys at Lotus laser systems
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they’ve taken the very brave step of
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entrusting this machine with me for one
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year they’ve lent it to me to play with
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as I’ve already started to tell you I
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know nothing about fiber laces so I’ve
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got this machine to just explore at my
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leisure now I have not in any way forced
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to make corporate videos Lotus laser
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system sounds like it should be a
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Chinese company these guys are only
Transcript for Introduction to Fiber Laser Marking (Cont…)
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probably about thirty miles up the road
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from me and they’re very easy to visit
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if I need to how much assistance have
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they given me with this machine the
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answer is very little at the moment
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they’ve installed it they’re showed me
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how to press all these buttons down at
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the bottom here they’re showing me
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roughly how the software works and
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they’ve given me a list of numbers and a
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little bit of paperwork that goes with
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the machine none of that paperwork tells
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me anything about how I make this
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machine perform the many tricks that it
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can perform but hey that’s going to be
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the fun of it ignorance is a great
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teacher too much knowledge gets in the
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way sometimes of digging into dark
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corners ignorance
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maybe allows me to dig into dark corners
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but I don’t even know a dark corners so
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we’ve got to build the foundations
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before we go anywhere near this machine
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now we’re going to start off with a very
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very simple atom got a small core or a
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nucleus and it’s got a charge a negative
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charge that Wizards around the outside
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of it in a little orbit just like a mini
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solar system the earth the moving
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running around the Earth now there are
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94 commonly found out
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months in this universe not just the
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world and each one of those elements has
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got a different mass in the centre and a
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different number of electrons floating
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in orbits around the outside of it now
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it’s very very usual for these atoms to
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not be on their own they like to exist
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with other atoms where they then become
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something called a molecule now
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molecules can either be two three four
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twenty atoms it depends on the
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complexity of what it is that you are
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looking at by whatever a material or a
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substance let’s forget about the larger
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picture and just come back to this very
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simple atom because this is all we need
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to understand lasing when this charge
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this electron gets a little bump of
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energy from somewhere it can move from
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this orbit to the next orbit out and
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here it is it’s now happily whizzing
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around in this orbit here but it’s not
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happy to stay in that orbit its natural
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orbit as this one so within a short
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period of time that could be anything
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from a millionth to a thousandth of a
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second it will drop back to this lower
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orbit now when it drops back it loses
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the energy that it gained when it went
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out to that orbit and it loses their
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energy in the form of a strange little
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thing called a and I’m going to draw it
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like this a photon of light we’re going
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to start looking at lasing in this form
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here which is the co2 gas tube laser the
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outer tube contains a gas mixture and
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that gas mixture also can run right
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through to the middle of the tube as
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well there are three tubes in there the
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outer one and the inner one are joined
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together right but around the outside of
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the inner tube we’ve got another tube
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which is full of water and that water is
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used to carry the heat away from the
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central tube
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now within this outer tube and obviously
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the inner tube as well we’ve got a mix
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of gases
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now all gases are basically non
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conductors of electricity now if we put
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25,000 volts across the end of this
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central tube the gas mix inside which
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contains nitrogen the nitrogen element
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of that gas mix will start to break down
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and release free electrons now these
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things here are electrons and what
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they’re basically doing is bursting free
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from their orbits and floating around
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and those free electrons are what are
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used to carry current through the tube
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electrical current through the tube so
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all of a sudden this nitrogen becomes a
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piece of almost resistance free wire it
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becomes conductive now we’re going to go
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to a real world tube now and I’m going
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to show you what happens when we put
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25,000 volts across the end the answer
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is nothing that you can see but then
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when we allow some current to flow
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through the nitrogen you’ll see that the
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colour or intensity of the glow in the
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tube is proportional to the amount of
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current that flows through the tube when
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you hear the little thing I’ve turned
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the 25,000 volts on now there was
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nothing happening when I turned to
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25,000 volts on
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okay so they’re now going to allow a
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very small amount of current to pass
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through the tube as well as the high
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voltage you can just about see a little
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bit of a pink glow at the end of the
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tube there I’m now going to allow more
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current to flow through the tube
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[Music]
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I’m now going to put the maximum
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allowable current through the tube
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[Music]
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I think you can see clearly the
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different intensity of light coming from
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the tube if I allow more than a certain
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amount of current to pass through the
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tube some very strange things happen
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okay so now you’ve seen this lovely pink
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glow that happens down the inside of the
Transcript for Introduction to Fiber Laser Marking (Cont…)
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tube basically this is lightning in a
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bottle the more current I put through it
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the more heat is being generated within
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the nitrogen itself and this element
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here the helium 80 percent of it is
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actually being used only as a means of
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transporting that heat out to the water
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jacket here where the heat is carried
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away and the whole system remains
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thermally stable now mixed in to this
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gas not only we got helium we’ve also
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got carbon dioxide a carbon dioxide
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molecule because it’s made up of carbon
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and two oxygen atoms bonded together so
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we’re now going to change away from our
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little orbital picture to just looking
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at the orbits themselves and what
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happens to these electrons it’s a much
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easier picture to understand here we’ve
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got the ground state where the electron
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starts then it goes up to its excited
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state which is the next orbit out then
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for a short period of time it may will
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drop down to this something called a
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metastable state which is an
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intermediate state and then it drops
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down all of the way and as it drops down
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it gives out this photon of light now
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I’m going to use this picture for two
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situations the first situation is where
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we put twenty-five thousand volts across
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the nitrogen column and what then
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happens is we shall knock some of these
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electrons out of their ground state
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completely into a free orbit so they’re
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floating around not all of them but just
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some of them and they’re there the
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electrons that will be carrying their
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current now as soon as we ask for
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current to flow those electrons they
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will rush towards the positive end which
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is the 25,000 volt end of the tube and
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as they rush along the tube so they will
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collide with other
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nitrogen electrons as they collide they
Transcript for Introduction to Fiber Laser Marking (Cont…)
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will promote those electrons up to an
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excited state now the action of
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promoting electrons up to an excited
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state is called pumping once they’ve
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been pumped up to their excited state
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they will stay there for a very short
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period of time now when they drop back
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to their ground state they will give up
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the energy that they acquired here in
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the form of a photon of light now the
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photon of light that they give up is
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pink that’s the action of the voltage
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and the current flowing through it which
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is pumping the nitrogen atoms up to a
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higher state and we’ve seen that pink go
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in action now in the tube it’s the
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collapse of excited nitrogen atoms going
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back to their ground state but the
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important thing here is this that we’ll
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think here which is the photon of light
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when they just drop back like this it’s
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a random action and that’s how you can
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see them because the pink is flying out
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the photons are flying out in all
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directions and some of them are
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finishing up at the back of your eye and
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you’re perceiving the pinkness of the
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photon it is the photon here this action
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of that photon which is going to then
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add energy to the carbon dioxide
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molecule and now we look at the same
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picture again so one of the electrons
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within the co2 molecule receives a
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little bit of pink energy from the
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nitrogen and that knocks the electron up
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to its excited state the next orbit
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where it stays for a short period of
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time drops down to its metastable state
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and then will just fall back to ground
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emitting an invisible ten point six
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micron wavelength of infrared light
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something that you can’t see but again
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look it will be totally random because
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there is nothing to say that it must go
Transcript for Introduction to Fiber Laser Marking (Cont…)
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in a particular direction you won’t be
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able to see it this time because it’s
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invisible but it’s still coming out of
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this tube it’s very very low
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random density so it’s not going to harm
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you now the word laser is acronym of
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light amplification by stimulated
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emission of radiation the important word
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here is stimulated what we’ve seen so
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far in both of these actions both the
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nitrogen and the carbon dioxide that
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we’ve mentioned so far has been random
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emission we get this light as the
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electron drops down from a high state to
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a ground state and we get this emission
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of radiation light and that’s what this
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is this is emission but it’s not
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stimulated it’s random so how do we get
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from random emission to stimulated
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emission but well here I’ve got a
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picture of a very simplified gas tube
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we’ve ignored the water and all we’ve
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done we’ve got the electrodes here and
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we’ve got our column of ionized gas down
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the center and we’ve got all the other
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gas around the outside but at the end of
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the tube we’ve got the mirror and a
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mirror now there’s just not one of these
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actions taking place we’ve got millions
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of this actions taking place at any
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given point in time and so just by
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chance one of these photons will finish
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up traveling in this direction rather
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than any of the other directions that
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I’ve mentioned there now if that photon
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travels in this direction it’s going to
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hit this mirror and as it hits this
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mirror it’s going to bounce back and
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pass through the tube to the other end
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where it’s going to bounce off that
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mirror and come back so let’s change
Transcript for Introduction to Fiber Laser Marking (Cont…)
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pictures again so here we’ve got our
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pink photon pumping the carbon dioxide
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electron up to its excited level it then
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drops down to its lowest state and then
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one of these random photon emissions
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hacks happens to accidentally bump into
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the mirror at an absolutely
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perpendicular plane and as it does so it
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will drive back down
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this way now as it passes one of these
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excited electrons it’s a bit like the
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Pied Piper saying come and join me it’s
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a very strange phenomenon that happens
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00:22:34.06 –> 00:22:40.930
when any when a photon travelling in
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00:22:37.51 –> 00:22:43.510
this direction can attract this to go
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down to its low level and emit a photon
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on the way that perfectly matches the
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one that’s travelling by it so as a
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consequence what you will get you’ll get
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these photons being collected and
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they’re completely synchronized as shown
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by this picture and they will be
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traveling in this direction until I hit
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00:23:01.93 –> 00:23:06.850
the mirror at this end and then they
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will all come back now as they’re
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traveling this way they will be
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collecting more photons and causing
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stimulated emissions from the electrons
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00:23:16.42 –> 00:23:21.520
that they are causing to drop down to
507
00:23:18.49 –> 00:23:25.900
their ground state and this action here
508
00:23:21.52 –> 00:23:29.020
of photons passing by excited electrons
509
00:23:25.9 –> 00:23:32.020
is the stimulated emission effect that
510
00:23:29.02 –> 00:23:35.620
you want that produces a laser now this
511
00:23:32.02 –> 00:23:38.140
is a laser beam everything is fully in
512
00:23:35.62 –> 00:23:41.950
phase it’s what they call a coherent
513
00:23:38.14 –> 00:23:44.380
beam and I suppose the best equivalent I
514
00:23:41.95 –> 00:23:47.170
can give to you of what this is the
515
00:23:44.38 –> 00:23:49.810
power that this has is you’re quite
516
00:23:47.17 –> 00:23:52.390
happy to stand out in the rain and have
517
00:23:49.81 –> 00:23:54.790
raindrops hit you but would you be happy
518
00:23:52.39 –> 00:23:57.460
to stand in front of a tsunami wave it’s
519
00:23:54.79 –> 00:24:00.010
the same stuff it’s water but it’s all
Transcript for Introduction to Fiber Laser Marking (Cont…)
520
00:23:57.46 –> 00:24:02.110
acting in harmony you can imagine the
521
00:24:00.01 –> 00:24:04.120
difference between rain and a tsunami
522
00:24:02.11 –> 00:24:06.240
wave now that’s not necessarily a
523
00:24:04.12 –> 00:24:08.980
perfect analogy but it gives the idea
524
00:24:06.24 –> 00:24:11.590
you know once you get things working in
525
00:24:08.98 –> 00:24:13.930
harmony they gain strength so we get
526
00:24:11.59 –> 00:24:16.450
this group of let’s call them soldiers
527
00:24:13.93 –> 00:24:18.730
all marching together down to this end
528
00:24:16.45 –> 00:24:20.050
they bounce off that mirror and of
529
00:24:18.73 –> 00:24:22.470
course by the time they bounce off that
530
00:24:20.05 –> 00:24:26.140
mirror not only have they collected more
531
00:24:22.47 –> 00:24:28.300
troops as they go down the road they hit
532
00:24:26.14 –> 00:24:30.730
the mirror and they come back now by the
533
00:24:28.3 –> 00:24:31.779
time they come back we’ve got more pink
534
00:24:30.73 –> 00:24:35.109
electrons
535
00:24:31.779 –> 00:24:37.869
promoted more carbon dioxide atoms up to
536
00:24:35.109 –> 00:24:40.239
their excited state and so as the army
537
00:24:37.869 –> 00:24:43.479
comes back it grows because it collects
538
00:24:40.239 –> 00:24:45.369
more soldiers all marching together and
539
00:24:43.479 –> 00:24:48.119
then it goes that wasn’t for words like
540
00:24:45.369 –> 00:24:51.729
this and this is the amplification of
541
00:24:48.119 –> 00:24:53.739
the light of the mirrors yes it’s no
542
00:24:51.729 –> 00:24:56.229
longer a random emission it’s a
543
00:24:53.739 –> 00:24:59.440
stimulated emission by virtue of other
544
00:24:56.229 –> 00:25:02.070
photons collecting photons so this is
545
00:24:59.44 –> 00:25:04.359
the strange action of how a laser works
546
00:25:02.07 –> 00:25:07.029
so back to our little picture here now
547
00:25:04.359 –> 00:25:09.669
and we can see this backwards and
548
00:25:07.029 –> 00:25:12.399
forwards motion up and down the tube the
549
00:25:09.669 –> 00:25:14.710
pink photons are contained within the
550
00:25:12.399 –> 00:25:16.119
tube but of course coming out the end of
551
00:25:14.71 –> 00:25:18.279
the tube here we’ve got invisible
552
00:25:16.119 –> 00:25:20.769
photons at ten point six microns
553
00:25:18.279 –> 00:25:22.749
infrared wavelength which are bouncing
554
00:25:20.769 –> 00:25:25.599
up and down inside the tube there the
555
00:25:22.749 –> 00:25:27.279
laser is the invisible army that’s
556
00:25:25.599 –> 00:25:29.649
marching up and down backwards and
557
00:25:27.279 –> 00:25:32.080
forwards here and when it gets to this
558
00:25:29.649 –> 00:25:34.359
end we don’t have a hundred percent
559
00:25:32.08 –> 00:25:36.879
mirror what we’ve got is a 90 percent
560
00:25:34.359 –> 00:25:38.469
mirror I say 90 percent because that’s
561
00:25:36.879 –> 00:25:40.809
just my guess I don’t know what the
562
00:25:38.469 –> 00:25:44.320
exact number is but the net result is
563
00:25:40.809 –> 00:25:48.249
that for example we get a 10% of the
564
00:25:44.32 –> 00:25:51.399
army escaping this is our laser beam
565
00:25:48.249 –> 00:25:53.399
that we are going to use okay now the
566
00:25:51.399 –> 00:25:57.549
rest of it is being sent back to
567
00:25:53.399 –> 00:26:02.080
regenerate more laser beam for us to use
Transcript for Introduction to Fiber Laser Marking (Cont…)
568
00:25:57.549 –> 00:26:05.080
and so this becomes a stable generation
569
00:26:02.08 –> 00:26:07.570
of a constant output laser beam within
570
00:26:05.08 –> 00:26:10.210
the hv power supply not only is it
571
00:26:07.57 –> 00:26:12.759
generating this 25,000 volts across the
572
00:26:10.21 –> 00:26:15.309
end here it’s also got a current
573
00:26:12.759 –> 00:26:17.409
limiting system in there and so when you
574
00:26:15.309 –> 00:26:19.570
specify that you want a certain power
575
00:26:17.409 –> 00:26:21.249
what you’re really specifying is you
576
00:26:19.57 –> 00:26:25.719
want to allow a certain amount of
577
00:26:21.249 –> 00:26:27.700
current to flow through the tube okay
578
00:26:25.719 –> 00:26:30.369
now as I’ve already described to you the
579
00:26:27.7 –> 00:26:32.710
current flowing through the tube is in
580
00:26:30.369 –> 00:26:33.969
fact causing a heating effect now I’m
581
00:26:32.71 –> 00:26:36.339
going to stop at this point in time
582
00:26:33.969 –> 00:26:39.700
because there is a very very important
583
00:26:36.339 –> 00:26:41.710
physics principle that I must explain to
584
00:26:39.7 –> 00:26:45.060
you now you all know what temperature is
585
00:26:41.71 –> 00:26:48.400
but how do you define temperature
586
00:26:45.06 –> 00:26:50.650
it’s hot it’s cold you measure it with a
587
00:26:48.4 –> 00:26:52.900
thermometer but there isn’t a definition
588
00:26:50.65 –> 00:26:57.820
of temperature let me try and explain in
589
00:26:52.9 –> 00:27:00.550
a very simple way there we go believe me
590
00:26:57.82 –> 00:27:04.510
that everything that you see every
591
00:27:00.55 –> 00:27:07.930
molecule every atom is busy doing this
592
00:27:04.51 –> 00:27:10.870
at room temperature it’s shaking it’s
593
00:27:07.93 –> 00:27:15.370
vibrating now as you lower the
594
00:27:10.87 –> 00:27:19.710
temperature to minus 273 degrees C what
595
00:27:15.37 –> 00:27:24.070
happens is all molecular motion ceases
596
00:27:19.71 –> 00:27:26.310
so therefore by default if we raise the
597
00:27:24.07 –> 00:27:28.660
temperature back up to room temperature
598
00:27:26.31 –> 00:27:32.680
everything all the molecules all the
599
00:27:28.66 –> 00:27:36.040
atoms start vibrating so the level of
600
00:27:32.68 –> 00:27:38.920
vibration in a molecule or atom is a
601
00:27:36.04 –> 00:27:42.010
definition of its temperature this power
602
00:27:38.92 –> 00:27:45.880
supply has got the ability to control
603
00:27:42.01 –> 00:27:48.700
the current through this tube but the
604
00:27:45.88 –> 00:27:51.880
power supply can actually supply a lot
605
00:27:48.7 –> 00:27:56.080
more current than the tube is allowed to
606
00:27:51.88 –> 00:27:59.530
carry now this is a strange property of
Transcript for Introduction to Fiber Laser Marking (Cont…)
607
00:27:56.08 –> 00:28:02.440
gas tubes which will not exist within
608
00:27:59.53 –> 00:28:04.300
the fiber laser but I need to explain it
609
00:28:02.44 –> 00:28:07.360
just briefly so that you understand the
610
00:28:04.3 –> 00:28:09.220
problem if we allow too much current to
611
00:28:07.36 –> 00:28:12.970
flow through the nitrogen the nitrogen
612
00:28:09.22 –> 00:28:17.500
becomes super excited because it becomes
613
00:28:12.97 –> 00:28:21.430
hotter remember hotter motion more
614
00:28:17.5 –> 00:28:24.910
motion hotter the energy of collision
615
00:28:21.43 –> 00:28:27.670
can actually break an oxygen away from
616
00:28:24.91 –> 00:28:30.580
the carbon dioxide molecule and turn it
617
00:28:27.67 –> 00:28:33.580
into carbon monoxide than oxygen this is
618
00:28:30.58 –> 00:28:37.210
a process called dissociation and this
619
00:28:33.58 –> 00:28:40.450
is what happens when you overdrive a gas
620
00:28:37.21 –> 00:28:41.710
tube you actually destroy the one thing
621
00:28:40.45 –> 00:28:44.590
that’s in there that gives you the
622
00:28:41.71 –> 00:28:48.160
lasing action which is carbon dioxide so
623
00:28:44.59 –> 00:28:51.970
you must never overdrive your carbon
624
00:28:48.16 –> 00:28:55.150
dioxide gas laser tube now this oxygen
625
00:28:51.97 –> 00:28:57.510
was floating around free in here it will
626
00:28:55.15 –> 00:28:59.790
possibly finish up floating around and
627
00:28:57.51 –> 00:29:03.240
and color and clogging up the cathode
628
00:28:59.79 –> 00:29:04.830
making it less efficient there are other
629
00:29:03.24 –> 00:29:07.290
mechanisms going on in there which I’m
630
00:29:04.83 –> 00:29:09.930
not going to explain but the net result
631
00:29:07.29 –> 00:29:11.840
is that you must be very careful when
632
00:29:09.93 –> 00:29:18.030
you’ve got a gas tube that you do not
633
00:29:11.84 –> 00:29:20.340
overdrive it now a typical gas 260 50
634
00:29:18.03 –> 00:29:24.510
Watts will be about a thousand
635
00:29:20.34 –> 00:29:26.910
millimeters long from end to end now the
636
00:29:24.51 –> 00:29:27.810
speed of light is such and we’ll talk
637
00:29:26.91 –> 00:29:31.290
about this later
638
00:29:27.81 –> 00:29:33.930
that it takes about three billions of a
639
00:29:31.29 –> 00:29:36.360
second for this action to take place
640
00:29:33.93 –> 00:29:38.190
backwards and forwards so three
641
00:29:36.36 –> 00:29:40.320
billionth of a second that way and three
642
00:29:38.19 –> 00:29:43.440
billionths of a second that way is all
643
00:29:40.32 –> 00:29:45.930
it takes for these photons to go so it’s
644
00:29:43.44 –> 00:29:47.400
virtually instantaneous okay so now
645
00:29:45.93 –> 00:29:50.040
you’re armed with all the information
646
00:29:47.4 –> 00:29:51.840
you need to understand how lacing works
647
00:29:50.04 –> 00:29:54.840
very quick summary
648
00:29:51.84 –> 00:29:57.210
you need a photon to bump into an
649
00:29:54.84 –> 00:29:58.710
electron which will promote the electron
650
00:29:57.21 –> 00:30:00.810
up to a higher energy level
Transcript for Introduction to Fiber Laser Marking (Cont…)
651
00:29:58.71 –> 00:30:02.400
something called the excited state where
652
00:30:00.81 –> 00:30:06.960
it could stay for a short period of time
653
00:30:02.4 –> 00:30:10.230
until a photon drifts by and encourages
654
00:30:06.96 –> 00:30:12.210
this excited state to drop down back to
655
00:30:10.23 –> 00:30:14.580
its ground state and as it drops back to
656
00:30:12.21 –> 00:30:17.400
its ground state it emits a photon of
657
00:30:14.58 –> 00:30:20.310
energy which matches the photon that
658
00:30:17.4 –> 00:30:23.970
encouraged the drop and then we need
659
00:30:20.31 –> 00:30:27.390
mirrors to encourage amplification those
660
00:30:23.97 –> 00:30:29.400
are the basics of a laser we’re now
661
00:30:27.39 –> 00:30:32.520
going to enter the amazing world of the
662
00:30:29.4 –> 00:30:36.210
fiber laser now as I said to you before
663
00:30:32.52 –> 00:30:37.770
a laser is a laser but there’s going to
664
00:30:36.21 –> 00:30:40.440
be a few differences here that we need
665
00:30:37.77 –> 00:30:41.970
to deal with it’s quite important that
666
00:30:40.44 –> 00:30:46.080
we understand a couple of things first
667
00:30:41.97 –> 00:30:48.990
of all the speed of light 186,000 miles
668
00:30:46.08 –> 00:30:50.850
per second in a vacuum let’s not get too
669
00:30:48.99 –> 00:30:53.820
picky about the vacuum surely let’s just
670
00:30:50.85 –> 00:30:57.510
assume that it’s also the same as 300
671
00:30:53.82 –> 00:30:59.640
million meters per second now this might
672
00:30:57.51 –> 00:31:01.620
seem a huge number but in fact it’s
673
00:30:59.64 –> 00:31:03.810
probably an easier number to work with
674
00:31:01.62 –> 00:31:05.850
let’s just move on to time everybody
675
00:31:03.81 –> 00:31:09.390
knows what one second is you can imagine
676
00:31:05.85 –> 00:31:10.840
that can you imagine what a millisecond
677
00:31:09.39 –> 00:31:13.740
is 1,000
678
00:31:10.84 –> 00:31:15.970
of a second how about when we go to a
679
00:31:13.74 –> 00:31:19.120
microsecond which is a millionth of a
680
00:31:15.97 –> 00:31:20.830
second I’m sure nobody can actually
681
00:31:19.12 –> 00:31:23.259
imagine what a millionth of a second
682
00:31:20.83 –> 00:31:25.929
feels like looks like or sounds like so
683
00:31:23.259 –> 00:31:28.779
we’re then go and times smaller than a
684
00:31:25.929 –> 00:31:32.070
microsecond and it’s called a nanosecond
685
00:31:28.779 –> 00:31:35.169
let’s relate the speed of light
686
00:31:32.07 –> 00:31:37.419
to time if we do some very simple maths
687
00:31:35.169 –> 00:31:41.139
like just just get rid of these notes
688
00:31:37.419 –> 00:31:42.789
here and we’ll get rid of those two
689
00:31:41.139 –> 00:31:46.119
notes there and two notes there
690
00:31:42.789 –> 00:31:50.350
what we find is that in one nanosecond
691
00:31:46.119 –> 00:31:51.850
we travel 0.3 of a meter so everybody
692
00:31:50.35 –> 00:31:55.570
can imagine what point three of a meter
693
00:31:51.85 –> 00:31:59.940
is it’s about a foot and that’s how far
Transcript for Introduction to Fiber Laser Marking (Cont…)
694
00:31:55.57 –> 00:32:03.340
light travels in a billionth of a second
695
00:31:59.94 –> 00:32:05.019
unimaginable numbers but they will
696
00:32:03.34 –> 00:32:07.659
become important to us as we start
697
00:32:05.019 –> 00:32:09.129
delving further into fiber optics we’ve
698
00:32:07.659 –> 00:32:11.470
now finished with the world of glass
699
00:32:09.129 –> 00:32:13.690
tubes and something that’s
700
00:32:11.47 –> 00:32:17.049
understandable and we’re going to move
701
00:32:13.69 –> 00:32:22.059
down into some atomically small world
702
00:32:17.049 –> 00:32:25.899
where things act very very strange I’ve
703
00:32:22.059 –> 00:32:30.549
drawn a picture here of a typical piece
704
00:32:25.899 –> 00:32:32.470
of fiber basically what we’ve got is two
705
00:32:30.549 –> 00:32:36.580
pieces of material here we’ve got this
706
00:32:32.47 –> 00:32:41.679
core in the center here which is shown
707
00:32:36.58 –> 00:32:45.129
as being either 8 microns diameter or 50
708
00:32:41.679 –> 00:32:47.139
microns diameter now eight microns
709
00:32:45.129 –> 00:32:49.659
diameter is only major and really small
710
00:32:47.139 –> 00:32:53.320
you may or may not be able to see just
711
00:32:49.659 –> 00:32:55.960
here two hairs this is a gray hair of my
712
00:32:53.32 –> 00:33:02.289
head and that is probably three times
713
00:32:55.96 –> 00:33:05.259
thicker than that 8 micron core the 50
714
00:33:02.289 –> 00:33:07.840
microns which here is probably much
715
00:33:05.259 –> 00:33:09.570
closer to this hair here which is a
716
00:33:07.84 –> 00:33:12.970
remnant of one of my ex-girlfriends
717
00:33:09.57 –> 00:33:15.429
this is the sort of magnitude that we’re
718
00:33:12.97 –> 00:33:17.889
talking about to be able to get ten or
719
00:33:15.429 –> 00:33:21.869
twelve kilowatts of energy out of
720
00:33:17.889 –> 00:33:23.750
something that diameter is unimaginable
721
00:33:21.869 –> 00:33:25.730
but it happens
722
00:33:23.75 –> 00:33:27.980
now the way in which the last laser tube
723
00:33:25.73 –> 00:33:30.980
was working was very simple we were
724
00:33:27.98 –> 00:33:35.510
creating pink light energy in this
725
00:33:30.98 –> 00:33:38.260
central tube and in here also was carbon
726
00:33:35.51 –> 00:33:42.050
dioxide and that was the carbon dioxide
727
00:33:38.26 –> 00:33:44.540
that was being stimulated to create a
728
00:33:42.05 –> 00:33:46.220
laser output we had a mirror at each end
729
00:33:44.54 –> 00:33:48.470
and the whole thing was bouncing
730
00:33:46.22 –> 00:33:50.210
backwards and forwards this being a 90%
731
00:33:48.47 –> 00:33:54.830
mirror and we were getting output from
732
00:33:50.21 –> 00:33:57.760
here so with the fiber laser what we do
733
00:33:54.83 –> 00:34:01.880
we inject the light from the outside
Transcript for Introduction to Fiber Laser Marking (Cont…)
734
00:33:57.76 –> 00:34:04.730
into this outside core this blue outer
735
00:34:01.88 –> 00:34:07.340
cladding as they call it okay now as
736
00:34:04.73 –> 00:34:11.389
that light bounces around it crosses
737
00:34:07.34 –> 00:34:14.600
over and interferes with this red core
738
00:34:11.389 –> 00:34:16.810
down the center now the red core down
739
00:34:14.6 –> 00:34:20.510
the center is a rather special material
740
00:34:16.81 –> 00:34:23.629
it’s a core made of silica glass doped
741
00:34:20.51 –> 00:34:25.909
with a rare earth called ytterbium now I
742
00:34:23.629 –> 00:34:29.330
know it says why there to begin to start
743
00:34:25.909 –> 00:34:33.080
with but why has actually said I so it’s
744
00:34:29.33 –> 00:34:36.260
ytterbium doped basically means it’s got
745
00:34:33.08 –> 00:34:37.570
a high percentage of ytterbium included
746
00:34:36.26 –> 00:34:40.490
in the glass
747
00:34:37.57 –> 00:34:42.980
whereas this outer sheath with a
748
00:34:40.49 –> 00:34:47.750
different refractive index I’m not going
749
00:34:42.98 –> 00:34:50.240
to explain that is just ordinary silica
750
00:34:47.75 –> 00:34:52.550
glass and it’s the difference in the
751
00:34:50.24 –> 00:34:55.639
refractive index of these two materials
752
00:34:52.55 –> 00:34:59.210
that causes the strange phenomena called
753
00:34:55.639 –> 00:35:02.360
total internal reflection and as you can
754
00:34:59.21 –> 00:35:06.080
see here we’ve got a red beam which is
755
00:35:02.36 –> 00:35:09.830
our power beam and it’s keeping to its
756
00:35:06.08 –> 00:35:14.210
own motorway which is the thin core down
757
00:35:09.83 –> 00:35:16.490
the center now this material in here
758
00:35:14.21 –> 00:35:18.070
called ytterbium has got some very
759
00:35:16.49 –> 00:35:22.820
interesting properties
760
00:35:18.07 –> 00:35:25.310
whereas with our co2 and a nitrogen we
761
00:35:22.82 –> 00:35:30.470
had something called an excited state
762
00:35:25.31 –> 00:35:33.350
and a a saw semi permanent state which
763
00:35:30.47 –> 00:35:34.750
is called a metastable state where it
764
00:35:33.35 –> 00:35:37.590
dropped down from there
765
00:35:34.75 –> 00:35:41.110
metastable state to the ground state
766
00:35:37.59 –> 00:35:44.410
with ytterbium we only have two states
767
00:35:41.11 –> 00:35:46.330
we’ve got a ground state and an excited
768
00:35:44.41 –> 00:35:48.840
state and relatively speaking this
769
00:35:46.33 –> 00:35:51.280
excited state can last quite a long time
770
00:35:48.84 –> 00:35:54.250
so we have no difference in the
771
00:35:51.28 –> 00:35:55.990
principle of lacing we’re just using a
772
00:35:54.25 –> 00:35:57.610
different material we’re using a solid
773
00:35:55.99 –> 00:36:01.240
material as opposed to a gas
Transcript for Introduction to Fiber Laser Marking (Cont…)
774
00:35:57.61 –> 00:36:03.250
so we pump light in and as you can see
775
00:36:01.24 –> 00:36:05.410
the light as gradually decreasing as we
776
00:36:03.25 –> 00:36:08.380
go along the fiber because we are
777
00:36:05.41 –> 00:36:12.150
gradually converting more and more of
778
00:36:08.38 –> 00:36:15.550
these ytterbium into high energy state
779
00:36:12.15 –> 00:36:17.530
which are then being released as the
780
00:36:15.55 –> 00:36:19.390
light bounces backwards and forwards of
781
00:36:17.53 –> 00:36:20.740
these two mirrors on the end here now
782
00:36:19.39 –> 00:36:22.720
although this is a general
783
00:36:20.74 –> 00:36:25.840
representation to give you the idea of
784
00:36:22.72 –> 00:36:28.060
how a fiber optic laser works it doesn’t
785
00:36:25.84 –> 00:36:30.070
actually work like this in reality at
786
00:36:28.06 –> 00:36:32.140
all now I’m not gonna go too far away
787
00:36:30.07 –> 00:36:34.390
from my diagram here but I am going to
788
00:36:32.14 –> 00:36:38.520
say that we don’t have real mirrors on
789
00:36:34.39 –> 00:36:41.890
the end of the fiber they manipulate the
790
00:36:38.52 –> 00:36:44.650
diameter of this central core in such a
791
00:36:41.89 –> 00:36:46.660
way it’s something called a brake
792
00:36:44.65 –> 00:36:48.850
grating which you can look that up and
793
00:36:46.66 –> 00:36:52.690
find out more about it which either
794
00:36:48.85 –> 00:36:55.300
causes complete reflection or partial
795
00:36:52.69 –> 00:36:58.240
reflection so we have the same effect as
796
00:36:55.3 –> 00:37:02.230
mirrors but without mirrors I’ve shown
797
00:36:58.24 –> 00:37:05.950
this is a very short section of fiber in
798
00:37:02.23 –> 00:37:09.490
reality this could be one two three six
799
00:37:05.95 –> 00:37:12.250
meters long it really depends on how
800
00:37:09.49 –> 00:37:14.410
much energy you want to store in the
801
00:37:12.25 –> 00:37:18.190
system okay now a few moments ago we
802
00:37:14.41 –> 00:37:21.040
talked about huge power capability out
803
00:37:18.19 –> 00:37:23.350
of these lasers but in reality it’s not
804
00:37:21.04 –> 00:37:25.780
quite as phenomenal as you might imagine
805
00:37:23.35 –> 00:37:28.690
we’re not talking about 12 kilowatts of
806
00:37:25.78 –> 00:37:31.960
continuous power we’re talking about the
807
00:37:28.69 –> 00:37:34.090
very very short duration pulse so in
808
00:37:31.96 –> 00:37:36.190
this world of fiber lasers marking
809
00:37:34.09 –> 00:37:38.770
machines which will come across two
810
00:37:36.19 –> 00:37:40.420
types of laser the most common type of
811
00:37:38.77 –> 00:37:42.820
laser is something called a q-switched
812
00:37:40.42 –> 00:37:44.710
laser now they’re generally the cheaper
813
00:37:42.82 –> 00:37:46.630
type of laser that doesn’t mean to say
814
00:37:44.71 –> 00:37:47.099
that bad it just means to say there have
815
00:37:46.63 –> 00:37:49.019
got
816
00:37:47.099 –> 00:37:52.349
a certain amount of limitation on their
817
00:37:49.019 –> 00:37:53.999
capabilities but first of all let’s take
818
00:37:52.349 –> 00:37:57.769
a look at the q-switch laser because
Transcript for Introduction to Fiber Laser Marking (Cont…)
819
00:37:53.999 –> 00:38:01.890
this is a fairly simple jump from a
820
00:37:57.769 –> 00:38:02.880
continuous wave laser to explain how
821
00:38:01.89 –> 00:38:05.609
this one works
822
00:38:02.88 –> 00:38:07.979
now as you can see I’ve modified the
823
00:38:05.609 –> 00:38:10.170
drawing very slightly and I’ve included
824
00:38:07.979 –> 00:38:12.269
this thing in here called a cue switch
825
00:38:10.17 –> 00:38:14.459
so I’m not going to explain how a cue
826
00:38:12.269 –> 00:38:16.109
switch works you can go and befuddle
827
00:38:14.459 –> 00:38:18.059
your own brain if you want I’m just
828
00:38:16.109 –> 00:38:20.400
going to regard this as being a piece of
829
00:38:18.059 –> 00:38:23.940
electronic cotton wool for the purpose
830
00:38:20.4 –> 00:38:26.519
of my very simple mental model basically
831
00:38:23.94 –> 00:38:28.920
it stops anything from reaching this
832
00:38:26.519 –> 00:38:31.289
mirror here and bear in mind these are
833
00:38:28.92 –> 00:38:33.390
not real mirrors these are things called
834
00:38:31.289 –> 00:38:35.459
Bragg gratings but I’ve shown them as
835
00:38:33.39 –> 00:38:38.430
mirrors because that’s what the net
836
00:38:35.459 –> 00:38:41.940
effect is so here we’ve got a cue switch
837
00:38:38.43 –> 00:38:44.910
and here we’ve got our blue pumping
838
00:38:41.94 –> 00:38:49.109
laser and remember what pumping is
839
00:38:44.91 –> 00:38:51.989
pumping is pushing all the electrons
840
00:38:49.109 –> 00:38:54.930
that are in here up to a higher excited
841
00:38:51.989 –> 00:38:56.969
state if we turn our electronic cotton
842
00:38:54.93 –> 00:38:59.459
wall on and prevent anything from
843
00:38:56.969 –> 00:39:01.229
reaching this mirror the only thing
844
00:38:59.459 –> 00:39:03.119
that’s going to happen is we’re going to
845
00:39:01.229 –> 00:39:03.660
pump all these electrons that are in
846
00:39:03.119 –> 00:39:06.569
here
847
00:39:03.66 –> 00:39:08.479
up to there excited state we’re
848
00:39:06.569 –> 00:39:12.989
effectively going to be storing energy
849
00:39:08.479 –> 00:39:14.670
in this piece of fiber-optic material so
850
00:39:12.989 –> 00:39:17.099
we’ve stored as much in as with energy
851
00:39:14.67 –> 00:39:18.809
as we can in here and now we’ll turn out
852
00:39:17.099 –> 00:39:22.949
a piece of electronic cotton wall off
853
00:39:18.809 –> 00:39:24.509
and some photons will escape and come
854
00:39:22.949 –> 00:39:26.969
through here and bounce off this mirror
855
00:39:24.509 –> 00:39:29.249
now as soon as a photon bounces off this
856
00:39:26.969 –> 00:39:31.019
mirror and runs back we know what the
857
00:39:29.249 –> 00:39:33.989
effect is going to be it’s going to
858
00:39:31.019 –> 00:39:36.539
trigger a cascade effect as it travels
859
00:39:33.989 –> 00:39:39.209
back to this mirror and so here we go
860
00:39:36.539 –> 00:39:41.999
this is the same basic principle that
861
00:39:39.209 –> 00:39:44.459
we’ve already discussed so there’s
862
00:39:41.999 –> 00:39:46.380
nothing new here except that we’ve put
863
00:39:44.459 –> 00:39:48.479
this switch in the way what is the
864
00:39:46.38 –> 00:39:51.779
effect of this switch now it’s much
865
00:39:48.479 –> 00:39:54.989
easier to show you this in a
866
00:39:51.779 –> 00:39:58.140
diagrammatic form here we’ve got the
867
00:39:54.989 –> 00:39:59.700
blue section over time and we’re busy
868
00:39:58.14 –> 00:40:02.490
pumping
Transcript for Introduction to Fiber Laser Marking (Cont…)
869
00:39:59.7 –> 00:40:05.069
electrons up to their high energy state
870
00:40:02.49 –> 00:40:06.900
they’re excited state and here we’ve got
871
00:40:05.069 –> 00:40:10.309
a green line which shows the general
872
00:40:06.9 –> 00:40:12.900
progression over time of the amount of
873
00:40:10.309 –> 00:40:15.150
excited electrons they get more and more
874
00:40:12.9 –> 00:40:16.710
and more and more until we reach a point
875
00:40:15.15 –> 00:40:18.960
where there are no more electrons to
876
00:40:16.71 –> 00:40:21.240
excite and so consequently this line
877
00:40:18.96 –> 00:40:23.910
would then level out once we’ve reached
878
00:40:21.24 –> 00:40:26.760
this maximum point here where we cannot
879
00:40:23.91 –> 00:40:29.130
actually excite any more electrons up to
880
00:40:26.76 –> 00:40:31.380
there excited state Mars will turn off
881
00:40:29.13 –> 00:40:33.809
the cue switch we remove the cotton wool
882
00:40:31.38 –> 00:40:36.000
and will allow the photons to pass
883
00:40:33.809 –> 00:40:38.309
through and hit the mirror now it’ll be
884
00:40:36.0 –> 00:40:40.530
initially there’ll be one or two photons
885
00:40:38.309 –> 00:40:42.119
a few photons that hit then they’ll
886
00:40:40.53 –> 00:40:43.650
start bouncing backwards and forwards
887
00:40:42.119 –> 00:40:45.299
and as they bounce backwards and
888
00:40:43.65 –> 00:40:47.790
forwards we’ll get this amplification
889
00:40:45.299 –> 00:40:49.530
effect well it takes a little bit of
890
00:40:47.79 –> 00:40:51.750
time for the amplification effect to
891
00:40:49.53 –> 00:40:53.880
build up but once the amplification
892
00:40:51.75 –> 00:40:56.760
effect builds up we get this cascade
893
00:40:53.88 –> 00:41:00.420
that happens where we get a tremendous
894
00:40:56.76 –> 00:41:02.730
rush a conversion rate of electrons and
895
00:41:00.42 –> 00:41:05.490
they start dropping down producing
896
00:41:02.73 –> 00:41:07.380
photons huge numbers of photons and of
897
00:41:05.49 –> 00:41:09.839
course as we’ve seen what we’re really
898
00:41:07.38 –> 00:41:12.809
producing here is that photon tsunami
899
00:41:09.839 –> 00:41:15.420
wave you know all these all the photons
900
00:41:12.809 –> 00:41:17.819
working together and they will produce a
901
00:41:15.42 –> 00:41:19.829
very huge peak but of course as soon as
902
00:41:17.819 –> 00:41:23.430
we start to get this peak which will
903
00:41:19.829 –> 00:41:27.720
reach a crossover point where the number
904
00:41:23.43 –> 00:41:29.819
of electrons available to rush out into
905
00:41:27.72 –> 00:41:32.400
the real world starts dropping rapidly
906
00:41:29.819 –> 00:41:35.130
so all of a sudden we’ll reach this peak
907
00:41:32.4 –> 00:41:37.740
and we will drop off just as quickly as
908
00:41:35.13 –> 00:41:40.290
we started this is only a 20 watt laser
909
00:41:37.74 –> 00:41:44.790
so let’s just see what would happen if
910
00:41:40.29 –> 00:41:48.720
this was a continuous 20 watt laser as
911
00:41:44.79 –> 00:41:52.200
opposed to a pulsed 20 watt laser so
912
00:41:48.72 –> 00:41:55.079
here we are we’re pumping and here we
913
00:41:52.2 –> 00:41:57.930
are pumping but this time because it’s a
914
00:41:55.079 –> 00:42:01.380
continuous output we’ve also got this
Transcript for Introduction to Fiber Laser Marking (Cont…)
915
00:41:57.93 –> 00:42:03.299
leakage here and so we won’t in this
916
00:42:01.38 –> 00:42:07.559
particular instance of a continuous wave
917
00:42:03.299 –> 00:42:10.400
ever reach saturation what what happen
918
00:42:07.559 –> 00:42:12.960
is we shall pump and we shall get the
919
00:42:10.4 –> 00:42:16.560
which will get the excited it
920
00:42:12.96 –> 00:42:20.070
runs up to a certain amount let’s call
921
00:42:16.56 –> 00:42:23.490
it that amount okay and it will be
922
00:42:20.07 –> 00:42:26.070
stable because as we’re pumping
923
00:42:23.49 –> 00:42:30.690
electrons up to this higher level so
924
00:42:26.07 –> 00:42:33.780
they’re leaking away and here we’ve got
925
00:42:30.69 –> 00:42:34.830
our 20 watt output okay now to try and
926
00:42:33.78 –> 00:42:36.630
make this a little bit more
927
00:42:34.83 –> 00:42:39.119
understandable what I’d like you to do
928
00:42:36.63 –> 00:42:40.710
is imagine a bath now if the water
929
00:42:39.119 –> 00:42:43.859
running into the bath is slightly
930
00:42:40.71 –> 00:42:46.290
greater than the oil will go at the plug
931
00:42:43.859 –> 00:42:48.119
hole there will be a balance that will
932
00:42:46.29 –> 00:42:50.369
be achieved we’ll get a certain level of
933
00:42:48.119 –> 00:42:52.380
water in the bath such that the water
934
00:42:50.369 –> 00:42:55.310
can disappear out the plug hole at the
935
00:42:52.38 –> 00:42:58.500
same rate that it comes in from the tap
936
00:42:55.31 –> 00:43:01.830
and that’s the stability that’s shown in
937
00:42:58.5 –> 00:43:04.140
this situation here now when we talk
938
00:43:01.83 –> 00:43:07.349
about a cue switch what we’re really
939
00:43:04.14 –> 00:43:09.750
doing is we’re putting the plug in so we
940
00:43:07.349 –> 00:43:13.500
put the plug in the bath and the bath no
941
00:43:09.75 –> 00:43:15.330
fills up to overflowing and then we
942
00:43:13.5 –> 00:43:18.089
remove the plug and as we remove the
943
00:43:15.33 –> 00:43:20.460
plug look we get a rush of water back to
944
00:43:18.089 –> 00:43:23.130
the plug hole so that’s how we can
945
00:43:20.46 –> 00:43:26.220
produce very high power out of a very
946
00:43:23.13 –> 00:43:27.540
low power input we can store it up for a
947
00:43:26.22 –> 00:43:34.589
period of time and then release it
948
00:43:27.54 –> 00:43:38.040
instantly instantly hmm remember we
949
00:43:34.589 –> 00:43:40.490
talked about the speed of light how far
950
00:43:38.04 –> 00:43:44.730
things travel in one nanosecond
951
00:43:40.49 –> 00:43:49.980
well these pulses here we’re talking
952
00:43:44.73 –> 00:43:52.589
about maybe maybe as little as 5 to 10
953
00:43:49.98 –> 00:43:55.170
nanoseconds let’s just say 10
954
00:43:52.589 –> 00:43:57.210
nanoseconds so that means look we’ve
955
00:43:55.17 –> 00:44:01.260
also got another 10 nanoseconds here
Transcript for Introduction to Fiber Laser Marking (Cont…)
956
00:43:57.21 –> 00:44:06.890
which is to build up time so it’s taking
957
00:44:01.26 –> 00:44:11.099
10 nanoseconds to get our system running
958
00:44:06.89 –> 00:44:14.010
so if this system is only one meter long
959
00:44:11.099 –> 00:44:16.859
for example and we know that it takes
960
00:44:14.01 –> 00:44:20.040
roughly 3 nanoseconds to travel a meter
961
00:44:16.859 –> 00:44:22.200
and if this is a 10 or 12 nanoseconds
962
00:44:20.04 –> 00:44:23.520
here it means we’re going to have Rea
963
00:44:22.2 –> 00:44:27.780
maybe
964
00:44:23.52 –> 00:44:30.960
two round-trips of a photon to build up
965
00:44:27.78 –> 00:44:32.490
to this critical level so that’s why
966
00:44:30.96 –> 00:44:35.820
we’ve got a delay here we can’t
967
00:44:32.49 –> 00:44:38.340
instantly get power out of the switch
968
00:44:35.82 –> 00:44:42.360
there is a delay after you switch on
969
00:44:38.34 –> 00:44:44.580
before things happen because the speed
970
00:44:42.36 –> 00:44:47.190
of light is actually now getting in the
971
00:44:44.58 –> 00:44:48.600
way of the pulse generation and then the
972
00:44:47.19 –> 00:44:51.870
width of the pulse is basically
973
00:44:48.6 –> 00:44:54.540
determined by the speed at which you
974
00:44:51.87 –> 00:44:57.030
could convert excited electrons into
975
00:44:54.54 –> 00:44:58.650
photons and that again is determined by
976
00:44:57.03 –> 00:45:00.270
the speed of light traveling up and down
977
00:44:58.65 –> 00:45:02.610
the fiber so there are certain physical
978
00:45:00.27 –> 00:45:06.690
limitations as to what can happen with
979
00:45:02.61 –> 00:45:08.940
this pulse now we could reduce the
980
00:45:06.69 –> 00:45:10.380
amount of pumping time in other words we
981
00:45:08.94 –> 00:45:13.260
could we could make the cue switch
982
00:45:10.38 –> 00:45:15.780
switch earlier and if we make the cue
983
00:45:13.26 –> 00:45:17.910
switch switch earlier then what it means
984
00:45:15.78 –> 00:45:19.470
is that we shan’t produce as much of a
985
00:45:17.91 –> 00:45:24.050
pulse which will produce a smaller pulse
986
00:45:19.47 –> 00:45:27.930
like this but it will still be a pulse
987
00:45:24.05 –> 00:45:31.020
but at a much lower peak power so that’s
988
00:45:27.93 –> 00:45:33.420
one variable that they could use to play
989
00:45:31.02 –> 00:45:41.490
with a cue switch the second variable is
990
00:45:33.42 –> 00:45:44.520
the repeat interval here of the pulse it
991
00:45:41.49 –> 00:45:47.220
really depends on how how long the fiber
992
00:45:44.52 –> 00:45:49.950
is and how quickly it takes to reach
993
00:45:47.22 –> 00:45:52.860
this saturation point so that’s the
994
00:45:49.95 –> 00:45:54.330
principle of q-switch laser ok so
995
00:45:52.86 –> 00:45:56.250
eventually we get on to the most
996
00:45:54.33 –> 00:45:58.230
difficult part of my quest which is
997
00:45:56.25 –> 00:46:01.110
trying to understand how a moped laser
Transcript for Introduction to Fiber Laser Marking (Cont…)
998
00:45:58.23 –> 00:46:04.250
works it’s not the same there’s any
999
00:46:01.11 –> 00:46:08.390
other laser that we’ve talked about yes
1000
00:46:04.25 –> 00:46:14.820
it’s got core yes it’s got a cladding
1001
00:46:08.39 –> 00:46:17.130
but it has no mirrors so that was a big
1002
00:46:14.82 –> 00:46:20.480
problem I had to start with with no
1003
00:46:17.13 –> 00:46:24.960
mirrors but then I realized something
1004
00:46:20.48 –> 00:46:27.840
significantly different this one has an
1005
00:46:24.96 –> 00:46:31.440
injection of a signal down into the core
1006
00:46:27.84 –> 00:46:34.280
itself not just a pump signal but
1007
00:46:31.44 –> 00:46:37.730
actually a signal which runs through
1008
00:46:34.28 –> 00:46:41.600
both laces and comes out this end in a
1009
00:46:37.73 –> 00:46:43.970
fully amplified laser format how does
1010
00:46:41.6 –> 00:46:46.850
this actually work it’s quite
1011
00:46:43.97 –> 00:46:50.750
complicated optically but in principle
1012
00:46:46.85 –> 00:46:53.000
it’s very simple for me to explain now
1013
00:46:50.75 –> 00:46:55.010
bear in mind this explanation that I’ve
1014
00:46:53.0 –> 00:46:57.230
given you as the explanation that I’m
1015
00:46:55.01 –> 00:47:00.260
giving myself this is how I’ve
1016
00:46:57.23 –> 00:47:03.950
interpreted after many hours of reading
1017
00:47:00.26 –> 00:47:06.530
and research into mopus nobody has told
1018
00:47:03.95 –> 00:47:08.930
me exactly how this thing works what I’m
1019
00:47:06.53 –> 00:47:13.400
just about to tell you fits all the
1020
00:47:08.93 –> 00:47:16.100
facts that I have we energize the core
1021
00:47:13.4 –> 00:47:18.740
in here up to its fullest extent with
1022
00:47:16.1 –> 00:47:21.200
these pumping lasers and this is a
1023
00:47:18.74 –> 00:47:23.930
signal input something they call a seed
1024
00:47:21.2 –> 00:47:25.670
laser more about this in a second so
1025
00:47:23.93 –> 00:47:28.930
once you’ve got the population in here
1026
00:47:25.67 –> 00:47:32.510
fully saturated inverted and saturated
1027
00:47:28.93 –> 00:47:35.440
at the same in this one we’ve got the
1028
00:47:32.51 –> 00:47:38.420
pump laser which is busy pumping all the
1029
00:47:35.44 –> 00:47:41.300
electrons in this core up to their
1030
00:47:38.42 –> 00:47:43.550
saturation high energy level we can then
1031
00:47:41.3 –> 00:47:47.680
inject a signal into this end
1032
00:47:43.55 –> 00:47:53.000
so this photodiode sends a powerful beam
1033
00:47:47.68 –> 00:47:55.040
into the end here and it then runs right
1034
00:47:53.0 –> 00:47:58.040
the way through here collecting photons
1035
00:47:55.04 –> 00:48:01.120
as it goes and comes out the other end
Transcript for Introduction to Fiber Laser Marking (Cont…)
1036
00:47:58.04 –> 00:48:04.300
with more photons than it went in with
1037
00:48:01.12 –> 00:48:08.090
but then it transfers across to another
1038
00:48:04.3 –> 00:48:10.370
much bigger and wider beam with more
1039
00:48:08.09 –> 00:48:13.490
pumping this secondary fine but then
1040
00:48:10.37 –> 00:48:16.190
actually amplifies the signal this first
1041
00:48:13.49 –> 00:48:19.690
fiber is signal conditioning that it’s
1042
00:48:16.19 –> 00:48:22.640
generating the pulse shape that we want
1043
00:48:19.69 –> 00:48:24.380
but this one amplifies the pol shake
1044
00:48:22.64 –> 00:48:26.600
there is a small amount of pulse change
1045
00:48:24.38 –> 00:48:28.640
shaping taking place in here as well but
1046
00:48:26.6 –> 00:48:31.850
most of the shaping takes place in here
1047
00:48:28.64 –> 00:48:34.610
now it’s not necessarily from what I
1048
00:48:31.85 –> 00:48:36.620
understand conscious shaping it’s
1049
00:48:34.61 –> 00:48:39.320
something that happens because of the
1050
00:48:36.62 –> 00:48:41.270
natural properties of the fiber this is
1051
00:48:39.32 –> 00:48:43.160
how I’ve explained it to myself so we’ve
1052
00:48:41.27 –> 00:48:46.160
got full population inversion in the
1053
00:48:43.16 –> 00:48:49.099
center core there we then inject a small
1054
00:48:46.16 –> 00:48:52.640
million from this red laser and that
1055
00:48:49.099 –> 00:48:56.530
signal might look like that and that
1056
00:48:52.64 –> 00:49:00.619
might be say one and then a second white
1057
00:48:56.53 –> 00:49:03.770
now this here could be for instance four
1058
00:49:00.619 –> 00:49:05.680
meters long and this cable here might be
1059
00:49:03.77 –> 00:49:08.599
six meters long
1060
00:49:05.68 –> 00:49:11.480
they’re quite long these fiber-optic
1061
00:49:08.599 –> 00:49:15.319
cables now we already know that one
1062
00:49:11.48 –> 00:49:20.390
nanosecond equals roughly 300
1063
00:49:15.319 –> 00:49:22.309
millimeters so four meters it’s going to
1064
00:49:20.39 –> 00:49:24.020
take thirteen or fourteen nanoseconds to
1065
00:49:22.309 –> 00:49:26.599
travel down there but what we’ve got to
1066
00:49:24.02 –> 00:49:29.450
imagine is this once we inject the
1067
00:49:26.599 –> 00:49:32.539
signal and the signal goes in and it is
1068
00:49:29.45 –> 00:49:34.460
300 millimetres long so there we are
1069
00:49:32.539 –> 00:49:35.750
we’ve got have 300 millimetre long
1070
00:49:34.46 –> 00:49:38.180
signal going in there
1071
00:49:35.75 –> 00:49:40.700
and it’s going to travel along and
1072
00:49:38.18 –> 00:49:43.400
remain 300 millimeters all the way along
1073
00:49:40.7 –> 00:49:44.900
there and then it’s going to do the same
1074
00:49:43.4 –> 00:49:48.680
all the way through here it’s going to
1075
00:49:44.9 –> 00:49:50.690
be a 300 millimetre long signal and it’s
1076
00:49:48.68 –> 00:49:53.089
got to pass right through the system as
1077
00:49:50.69 –> 00:49:55.400
this signal passes along here the
1078
00:49:53.089 –> 00:49:58.670
leading edge of this signal is going to
Transcript for Introduction to Fiber Laser Marking (Cont…)
1079
00:49:55.4 –> 00:50:02.119
encounter the most number of excited
1080
00:49:58.67 –> 00:50:05.720
electrons ready to drop down and produce
1081
00:50:02.119 –> 00:50:08.089
a photon which will join this army so
1082
00:50:05.72 –> 00:50:11.779
the leading edge of this signal will
1083
00:50:08.089 –> 00:50:13.460
collect the most number of photons so
1084
00:50:11.779 –> 00:50:15.289
but the time this signal gets to the
1085
00:50:13.46 –> 00:50:17.059
other end here the signal is going to
1086
00:50:15.289 –> 00:50:23.809
come out the other end is likely to look
1087
00:50:17.059 –> 00:50:27.410
something like this it’s still one
1088
00:50:23.809 –> 00:50:29.750
nanosecond wide but the leading edge has
1089
00:50:27.41 –> 00:50:31.970
collected more photons than the trailing
1090
00:50:29.75 –> 00:50:34.309
edge of the signal and so that is how
1091
00:50:31.97 –> 00:50:36.710
that signal goes into here
1092
00:50:34.309 –> 00:50:37.940
and the chances are that what it’s going
1093
00:50:36.71 –> 00:50:40.099
to do is kind of come out the other end
1094
00:50:37.94 –> 00:50:42.200
very similar to that but maybe with a
1095
00:50:40.099 –> 00:50:45.289
little bit more trailing edge Distortion
1096
00:50:42.2 –> 00:50:47.869
here is the chart that I was given which
1097
00:50:45.289 –> 00:50:51.829
made no sense to me when I received it I
1098
00:50:47.869 –> 00:50:54.470
was told that hey if you run at 850
1099
00:50:51.829 –> 00:50:55.940
kilohertz with a 2 nanosecond signal
1100
00:50:54.47 –> 00:50:59.020
that’s when you’re going to develop
1101
00:50:55.94 –> 00:50:59.020
print our
1102
00:50:59.4 –> 00:51:05.109
so when I look at the other end of the
1103
00:51:01.779 –> 00:51:09.940
scale here which is 350 nanosecond
1104
00:51:05.109 –> 00:51:12.970
signal pulse that seems quite staggering
1105
00:51:09.94 –> 00:51:18.160
because when we started putting real
1106
00:51:12.97 –> 00:51:21.339
numbers to that 350 nanoseconds and we
1107
00:51:18.16 –> 00:51:24.369
know the speed of light causes 0.3 of a
1108
00:51:21.339 –> 00:51:26.859
meter per nanosecond that means that
1109
00:51:24.369 –> 00:51:30.700
signal is actually a hundred and five
1110
00:51:26.859 –> 00:51:33.460
meters long in other words I start the
1111
00:51:30.7 –> 00:51:36.670
signal off here and it’s actually coming
1112
00:51:33.46 –> 00:51:38.829
out and burning on the job before I’ve
1113
00:51:36.67 –> 00:51:41.470
actually finished the signal coming into
1114
00:51:38.829 –> 00:51:44.079
the end here because this is only 10
1115
00:51:41.47 –> 00:51:45.970
meters long now if I’ve got the physics
1116
00:51:44.079 –> 00:51:47.739
of that wrong perhaps somebody will tell
1117
00:51:45.97 –> 00:51:50.829
me but that’s the way that it looks to
1118
00:51:47.739 –> 00:51:52.869
me that’s how we can get these really
1119
00:51:50.829 –> 00:51:55.960
weird shaped pulses because the leading
1120
00:51:52.869 –> 00:51:58.059
edge passes through here so I’ve only
Transcript for Introduction to Fiber Laser Marking (Cont…)
1121
00:51:55.96 –> 00:52:05.140
got a signal which is sits which sits
1122
00:51:58.059 –> 00:52:08.109
there for 350 nanoseconds like this it’s
1123
00:52:05.14 –> 00:52:10.269
now a very long pulse but the trailing
1124
00:52:08.109 –> 00:52:16.359
edge of their pulse is going to look
1125
00:52:10.269 –> 00:52:18.269
like this because the tail end of the
1126
00:52:16.359 –> 00:52:22.680
pulse is going to collect a lot less
1127
00:52:18.269 –> 00:52:25.930
photons than the leading edge because I
1128
00:52:22.68 –> 00:52:28.269
presume that the path blazer is not
1129
00:52:25.93 –> 00:52:31.809
going to be working while the signals
1130
00:52:28.269 –> 00:52:34.119
working I don’t know I don’t know what
1131
00:52:31.809 –> 00:52:36.400
the mechanism is but this clearly
1132
00:52:34.119 –> 00:52:38.380
describes to me a mechanism by which we
1133
00:52:36.4 –> 00:52:41.410
can generate these strange-looking
1134
00:52:38.38 –> 00:52:45.039
pulses that come out of this signal
1135
00:52:41.41 –> 00:52:48.309
element here now I suspect that this
1136
00:52:45.039 –> 00:52:49.630
will be energized all the time but they
1137
00:52:48.309 –> 00:52:51.430
don’t know whether these will be in the
1138
00:52:49.63 –> 00:52:54.130
Joseph these are the sort of facts that
1139
00:52:51.43 –> 00:52:55.839
I can’t find anything about nobody out
1140
00:52:54.13 –> 00:52:57.910
there is telling me how this thing works
1141
00:52:55.839 –> 00:53:01.029
so I’m having to try and work it out
1142
00:52:57.91 –> 00:53:02.920
from yourself now maybe know that
1143
00:53:01.029 –> 00:53:04.359
somebody’s seen me struggling they might
1144
00:53:02.92 –> 00:53:06.400
be able to enlighten me and give me a
1145
00:53:04.359 –> 00:53:09.549
very very simple explanation as to how
1146
00:53:06.4 –> 00:53:10.750
this works but in the absence of anybody
1147
00:53:09.549 –> 00:53:13.210
else’s explanation
1148
00:53:10.75 –> 00:53:15.070
I’m happy to work with this as a model
1149
00:53:13.21 –> 00:53:16.780
the only thing that I can absolutely be
1150
00:53:15.07 –> 00:53:18.820
sure is I’m going to get a leading edge
1151
00:53:16.78 –> 00:53:22.800
pulse which is a lot higher than the
1152
00:53:18.82 –> 00:53:25.570
trailing edge pulse and that agrees with
1153
00:53:22.8 –> 00:53:28.599
several facts that I’ve already got this
1154
00:53:25.57 –> 00:53:30.820
is the 350 milliseconds which looks like
1155
00:53:28.599 –> 00:53:33.460
this it’s got a very long trailing edge
1156
00:53:30.82 –> 00:53:35.770
whereas in fact the tune in the second
1157
00:53:33.46 –> 00:53:38.619
pulse which is this one here has got a
1158
00:53:35.77 –> 00:53:40.869
very very short trailing edge when we
1159
00:53:38.619 –> 00:53:44.200
look across this graph typically we’re
1160
00:53:40.869 –> 00:53:46.960
talking about 12 kilowatts peak power
1161
00:53:44.2 –> 00:53:49.240
for most of these pulses and then we get
1162
00:53:46.96 –> 00:53:52.300
to this lower range which are about 8
1163
00:53:49.24 –> 00:53:54.520
kilowatts but over a much wider period
1164
00:53:52.3 –> 00:53:58.030
so one has to assume that we can
1165
00:53:54.52 –> 00:54:01.240
actually do more sustained damage with
Transcript for Introduction to Fiber Laser Marking (Cont…)
1166
00:53:58.03 –> 00:54:03.490
this range of pulses that we can with
1167
00:54:01.24 –> 00:54:07.030
these these are going to produce very
1168
00:54:03.49 –> 00:54:08.710
sharp deep pulses can I say there’s not
1169
00:54:07.03 –> 00:54:11.650
very much energy and there’s a lot of
1170
00:54:08.71 –> 00:54:13.240
power but not very much sustained energy
1171
00:54:11.65 –> 00:54:15.460
in there to do damage to the material
1172
00:54:13.24 –> 00:54:17.500
but that’s one of the subjects I’m going
1173
00:54:15.46 –> 00:54:19.480
to have to investigate how much damage
1174
00:54:17.5 –> 00:54:21.490
can I do to the material with each one
1175
00:54:19.48 –> 00:54:24.869
of these pulses now that I’ve begun to
1176
00:54:21.49 –> 00:54:27.880
understand this my list of numbers here
1177
00:54:24.869 –> 00:54:29.230
begins to make a little bit of sense so
1178
00:54:27.88 –> 00:54:32.740
let’s take a quick look at this 2
1179
00:54:29.23 –> 00:54:35.470
nanosecond pulse here what it means is
1180
00:54:32.74 –> 00:54:37.570
that inter if I’ve got 2 nanoseconds and
1181
00:54:35.47 –> 00:54:40.960
I’ve got an eight hundred and fifty
1182
00:54:37.57 –> 00:54:44.200
kilohertz maximum allowable frequency
1183
00:54:40.96 –> 00:54:50.520
that I can run at approximately that’s
1184
00:54:44.2 –> 00:54:53.740
roughly one microsecond for every cycle
1185
00:54:50.52 –> 00:54:56.589
approximately so that means that I’ve
1186
00:54:53.74 –> 00:55:00.010
got roughly a ratio of two nanoseconds
1187
00:54:56.589 –> 00:55:03.130
to a thousand nanoseconds which is
1188
00:55:00.01 –> 00:55:05.440
roughly 500 to 1 or in real terms let’s
1189
00:55:03.13 –> 00:55:07.930
go back to here and say that if I put a
1190
00:55:05.44 –> 00:55:11.740
two nanosecond pulse in there that means
1191
00:55:07.93 –> 00:55:14.710
I’ve got 998 nanoseconds in which to
1192
00:55:11.74 –> 00:55:17.380
recharge or rien vert the population in
1193
00:55:14.71 –> 00:55:18.609
here to make it fully charged again so
1194
00:55:17.38 –> 00:55:21.820
that I can understand
1195
00:55:18.609 –> 00:55:23.150
alright that’s why I must make sure that
1196
00:55:21.82 –> 00:55:27.210
I don’t exceed
1197
00:55:23.15 –> 00:55:30.090
850 kilohertz not it runs slower because
1198
00:55:27.21 –> 00:55:33.540
if I run at 500 kilohertz then there’s
1199
00:55:30.09 –> 00:55:35.160
even more time for the light to invert
1200
00:55:33.54 –> 00:55:38.010
that population and get full saturation
1201
00:55:35.16 –> 00:55:40.650
in there ready for the next pulse so I
1202
00:55:38.01 –> 00:55:43.080
can always run these numbers at smaller
1203
00:55:40.65 –> 00:55:45.780
values but I mustn’t run these numbers
1204
00:55:43.08 –> 00:55:48.090
at larger frequencies now in Lotus
1205
00:55:45.78 –> 00:55:49.980
installed the machine for me they
1206
00:55:48.09 –> 00:55:54.180
provided me with this very useful piece
1207
00:55:49.98 –> 00:55:56.940
of support documentation which basically
1208
00:55:54.18 –> 00:55:59.160
tells me understanding the differences
1209
00:55:56.94 –> 00:56:01.800
between q-switched and micro lases which
Transcript for Introduction to Fiber Laser Marking (Cont…)
1210
00:55:59.16 –> 00:56:03.960
is hopefully can be very interesting and
1211
00:56:01.8 –> 00:56:07.910
on the front page they give me this
1212
00:56:03.96 –> 00:56:11.250
diner if I had a physics doctor in
1213
00:56:07.91 –> 00:56:14.430
optoelectronics I might be able to
1214
00:56:11.25 –> 00:56:18.930
understand this but this is pretty
1215
00:56:14.43 –> 00:56:25.980
meaningless too I think most people meet
1216
00:56:18.93 –> 00:56:28.260
the wording used here hf f BG ydf these
1217
00:56:25.98 –> 00:56:30.510
are all acronyms which mean absolutely
1218
00:56:28.26 –> 00:56:33.540
nothing to me I mean I know that this
1219
00:56:30.51 –> 00:56:41.040
happens to be a a hyper ramen scattering
1220
00:56:33.54 –> 00:56:44.040
fiber Bragg grating Wow fantastic what
1221
00:56:41.04 –> 00:56:46.670
is it what does it mean we’ve got the
1222
00:56:44.04 –> 00:56:51.030
same thing here hello Raman scattering
1223
00:56:46.67 –> 00:56:53.430
fiber Bragg grating well technically
1224
00:56:51.03 –> 00:56:55.470
these two things here are the mirrors I
1225
00:56:53.43 –> 00:56:57.540
think I’ve described to you the break
1226
00:56:55.47 –> 00:56:59.030
grating well you need to go and have a
1227
00:56:57.54 –> 00:57:03.240
look up and see what that is
1228
00:56:59.03 –> 00:57:08.310
these are this Y D F stands for
1229
00:57:03.24 –> 00:57:13.650
ytterbium doped fiber okay it’s easy
1230
00:57:08.31 –> 00:57:17.490
when you know and this a o M it’s an
1231
00:57:13.65 –> 00:57:19.230
acoustic octo modulator what’s that well
1232
00:57:17.49 –> 00:57:23.450
that’s my piece of electronic cotton
1233
00:57:19.23 –> 00:57:26.880
wool my simplified drawings are that
1234
00:57:23.45 –> 00:57:28.770
exactly without all the frigging bits in
1235
00:57:26.88 –> 00:57:32.580
the same way that look this is a motor
1236
00:57:28.77 –> 00:57:35.610
system as described by presumably jpt
1237
00:57:32.58 –> 00:57:36.390
originally it there’s a lot more stuff
1238
00:57:35.61 –> 00:57:39.809
in here
1239
00:57:36.39 –> 00:57:41.460
deleting my simple diagram it’s called a
1240
00:57:39.809 –> 00:57:44.999
YB doped
1241
00:57:41.46 –> 00:57:47.369
DCF net what’s a DCF well it’s a
1242
00:57:44.999 –> 00:57:51.380
diffusion corrected fiber there’s a very
1243
00:57:47.369 –> 00:57:54.119
good site on on the web called photonics
1244
00:57:51.38 –> 00:57:56.880
encyclopedia you’ll find a lot of this
1245
00:57:54.119 –> 00:57:58.920
stuff defined in there but the problem
1246
00:57:56.88 –> 00:58:00.869
is you won’t understand most of the
Transcript for Introduction to Fiber Laser Marking (Cont…)
1247
00:57:58.92 –> 00:58:03.329
stuff that’s in there because it’s
1248
00:58:00.869 –> 00:58:05.789
written in Klingon for people that read
1249
00:58:03.329 –> 00:58:08.910
Klingon and I’m afraid I’m just a very
1250
00:58:05.789 –> 00:58:10.799
humble old-school engineer and most of
1251
00:58:08.91 –> 00:58:13.319
this stuff means nothing to me so I like
1252
00:58:10.799 –> 00:58:15.749
to reduce it back to the very basic
1253
00:58:13.319 –> 00:58:17.670
elements that I can understand and I
1254
00:58:15.749 –> 00:58:20.160
hope I’ve done the same thing for you
1255
00:58:17.67 –> 00:58:23.489
jpt claim all sorts of things for their
1256
00:58:20.16 –> 00:58:25.079
little bit of kit for the next phase I’m
1257
00:58:23.489 –> 00:58:27.359
going to be working with the machine to
1258
00:58:25.079 –> 00:58:30.329
see just how close I can get to some of
1259
00:58:27.359 –> 00:58:32.279
this stuff so I look forward to seeing
1260
00:58:30.329 –> 00:58:34.880
you in the next session thank you very
1261
00:58:32.279 –> 00:58:34.880
much for your time
Transcript for Introduction to Fiber Laser Marking
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UNDER NO CIRCUMSTANCE SHALL WE HAVE ANY LIABILITY TO YOU FOR ANY LOSS OR DAMAGE OF ANY KIND INCURRED AS A RESULT OF THE USE OF THE SITE OR RELIANCE ON ANY INFORMATION PROVIDED ON THE SITE. YOUR USE OF THE SITE AND YOUR RELIANCE ON ANY INFORMATION ON THE SITE IS SOLELY AT YOUR OWN RISK.
EXTERNAL LINKS DISCLAIMER
The Site may contain (or you may be sent through the Site) links to other websites or content belonging to or originating from third parties or links to websites and features in banners or other advertising. Such external links are not investigated, monitored, or checked for accuracy, adequacy, validity, reliability, availability or completeness by us.
WE DO NOT WARRANT, ENDORSE, GUARANTEE, OR ASSUME RESPONSIBILITY FOR THE ACCURACY OR RELIABILITY OF ANY INFORMATION OFFERED BY THIRD-PARTY WEBSITES LINKED THROUGH THE SITE OR ANY WEBSITE OR FEATURE LINKED IN ANY BANNER OR OTHER ADVERTISING.
WE WILL NOT BE A PARTY TO OR IN ANY WAY BE RESPONSIBLE FOR MONITORING ANY TRANSACTION BETWEEN YOU AND THIRD-PARTY PROVIDERS OF PRODUCTS OR SERVICES.
AFFILIATES DISCLAIMER
The Site may contain links to affiliate websites, and we receive an affiliate commission for any purchases made by you on the affiliate website using such links. Our affiliates include the following:
- makeCNC who provide Downloadable Patterns, Software, Hardware and other content for Laser Cutters, CNC Routers, Plasma, WaterJets, CNC Milling Machines, and other Robotic Tools. They also provide Pattern Files in PDF format for Scroll Saw Users. They are known for their Friendly and Efficient Customer Service and have a comprehensive back catalogue as well as continually providing New Patterns and Content.
- Cloudray Laser: a world-leading laser parts and solutions provider, has established a whole series of laser product lines, range from CO2 engraving & cutting machine parts, fiber cutting machine parts and laser marking machine parts.