Beam Combiner: Improving the Laser Beam on an RF Laser Source!

The Tangerine Tiger Series with Russ Sadler

In this Series, Russ has purchased a new 500 x 300mm, 50W laser machine from eBay with a view to modifying and upgrading it. He actually rips out the glass laser tube and high voltage power supply and replaces them with an RF laser source and PSU from Cloudray. In this session, Russ adds some correction optics in the form of a Laser Beam Combiner.

If you are considering purchasing a CO2 laser machine with an RF laser source from one of the big boy suppliers, I would suggest you check out this series before making a decision!


Having established that an RF laser beam is not as parallel as the beam from a glass tube system, it was found necessary to add some correction optics. Here we test the power cost and the effectiveness of this addition and finally get the beam setup. I impatiently take a peep into the future.

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Rf laser source with beam combiner attached
RF Laser Source with Beam Combiner Attached

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Transcript for Let’s See What We Have – Beam Combiner

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0:00welcome to another session with my

0:02little tangerine tiger

0:04um it’s been a couple of weeks now since

0:07i’ve really played with this machine

0:08because i’ve had

0:09other things to deal with but hey we’re

0:12getting back on the case now

0:14last time if you remember um we managed

0:17to establish that the

0:18expanding beam could be controlled

0:22with a beam expander and i made my own

0:25little crude holder

0:26to put the three times beam expander in

0:29front of the rf laser

0:31it was adequate to prove the point that

0:34the beam expander worked

0:35and that we went from a two millimeter

0:38beam to about a six millimeter beam

0:41whether we looked at it about 100

0:42millimeters away or in fact i checked it

0:44about three meters away as well

0:46it looked to be doing a pretty good job

0:48of making the brim

0:49beam pretty parallel so

0:54i then inquired of cloud ray

0:58if there was such a thing as a piece of

1:01standard kit that would allow

1:04me to fix that onto the front of this

1:07you can buy it everywhere type rf laser

1:10there must be some adapter

1:12plate that allows me to connect one of


1:15beam expanders straight onto the front


1:18they didn’t appear to be so i designed

1:20something and sent it to cloud and asked

1:22them if they’d make a prototype

1:24the good news is they didn’t

1:29what they found instead was a standard

1:31plate of some sort from somewhere

1:33now i don’t know where they found it

1:34from but they’ve

1:36sent me a a standard plate

1:40b a two times magnifier

1:45so we can test the two and the three

1:48to see what effect they have now here is

1:51the plate that they sent me as you can


1:53it fits perfectly it only locates on

1:56these four holes at the edge here

1:58but they’re pretty accurately machined

2:00holes and when i

2:01check in there it looks as though it’s

2:03pretty concentric

2:05now the great news is all i have to do

2:08is to screw this in and job is done

2:12but i’m not going to do that to start

2:14with now although i’m anxious to get on

2:16and use this machine

2:18i don’t think i really ought to rush it

2:20because i really ought to understand

2:22how this thing works before i start

2:24trying to make it do

2:25something i want to go about this

2:27journey of discovery in a much more

2:29logical fashion

2:30than i did when i knew very little and

2:33was floundering around in the dark with

2:34my china blue machine

2:36my first task will be to measure the


2:39that is coming out of this device it

2:41says it’s 30 watts

2:43i think that that’s 30 watts cw

2:46continuous wave mode

2:47now i’ve got no idea how this machine is

2:50programmed at the moment and what’s

2:51going to come out of here

2:53but because this is a pulsing system

2:55controlled by the pwm

2:57so it could well be that the pulse is 30

2:59watts but

Transcript for Let’s See What We Have – Beam Combiner (Cont…)

3:01the pulses are regularly spaced out for


3:04such that we’ve got 50 on and 50

3:07off now what that means is although

3:09we’ve got 30 watts per pulse we shall

3:11only have an average power of 15 watts

3:13so what i measure on here

3:17is a little bit of an unknown at the

3:19moment that doesn’t make any difference

3:21because what we want to find out is the

3:23relative change

3:24of power as i move further away from the


3:29technically you wouldn’t expect the

3:30laser beam to lose its power with


3:33i know it changes its diameter with

3:35distance but the power should still be

3:37there in the beam

3:39i want to prove that before we start

3:42because i want to get to 1.3 meters

3:44which is about where you are at the


3:46because i don’t want to lose power as i

3:48go around this very small machine

3:50now i’ve already got my little doohickey

3:52test program set up on the machine that

3:54runs for 20.5

3:56seconds well i’m going to check first of

3:58all what’s happening straight out of the

3:59tube here

4:00now i’ve got something in the region of

4:02about maybe five

4:04or six seconds before the beam will

4:06start coming out of here

4:07one other thing that i’ve noticed and

4:09i’ll have to explore

4:10further this is completely cold at this

4:13moment in time

4:15i have read somewhere that it takes


4:1810 minutes for this to warm up to its

4:21proper output value seems a bit strange

4:25but hey that’s what

4:26one of the specifications i read said

4:29for the moment we’re going to check it

4:31from cold dead cold because this has

4:33been sitting here for

4:34well as i said a couple of weeks now

4:4018.2 to 38.

4:43we started off at 18.2 we finished up at


4:48the difference in temperature the

4:49temperature rise is 19.8

4:52and we’re using the times two scale

4:55which means if i multiply 19.8 by 2 i

4:58get 39.6

5:01this is a 30 watt machine so hey

5:04we’re doing something pretty remarkably

5:06good here

5:09well this time we’re starting off at

5:10about 18.6

5:14now from all the work that i’ve done

5:16previously i would expect to lose

5:18something in the region of about four


5:22per lens

5:27just as a guide

5:31so dividing that by that

5:36gives me 95

5:40so that means i’ve lost five percent

5:43over two lenses which is not bad

5:46that’s the times three device

5:50let’s try the times two device

5:53and see what that gives us here’s the

5:56times two

5:57that i’m just about to tighten this up

5:59onto its shoulder

Transcript for Let’s See What We Have – Beam Combiner (Cont…)

6:00if i loosen it off just a little bit

6:05but i could physically move this maybe

6:08half to three quarters of a millimeters

6:11either way so that’s a pretty

6:14dodgy old thread in there that looks

6:16like a much bigger loss

6:1836.6 37.8

6:21that’s another one another what that’s

6:24been lost

6:24because we’ve done times two do i

6:26believe that



6:32because it’s possible remember what i

6:34said to start with this thing has got a

6:36warm up period

6:37that things might have changed in the

6:39five or ten minutes that this has been


6:42so the check that i shall now make

6:46is take the beam combiner off and check

6:49the wattage again do i get the same

6:51value as

6:52two times is about what i expected four

6:54percent loss per lens

6:57okay so i’ve got a piece of card there

6:58set up uh

7:001.3 meters away from the front of the


7:04and i’ve got no beam combiner on it at

7:06all i’m going to see it fire 100

7:08power at it just quickly just to find

7:11out where i am

7:13and there is the answer now we do a bit

7:15of a real target test

7:17because first of all i stuck a piece of


7:20onto the card so that there’s somewhere

7:22for the energy to get absorbed

7:24if it burns through the card and i don’t

7:27want to set fire to my cardboard

7:29but i’m also using a card there which is

7:32in front

7:32which has got a quite high kaolin

7:34content in other words

7:35it won’t catch fire i hope

7:39so i’m hoping to be able to get a decent

7:41scorch mark which tells me the real size

7:43of the beam when i can hold it on for

7:45long enough

7:55there we go i think that’s probably

7:57about as big as the bean is going to get

7:59i would say that that’s close on 10


8:03we know we’re starting off with

8:04approximately a two millimeter beam i’m

8:06gonna put the times three beam combiner

8:08on and i’m gonna move the laser very


8:11to the right

8:23i’ll measure it properly later on but

8:25it’s somewhere between seven and eight


8:27it’s not too far away

8:36i have to say that that is substantially


8:39but i would probably put that at about

8:43six millimeters we’ll just check

8:47we’re still in the right place yes

8:57i’m quite pleased with that

Transcript for Let’s See What We Have – Beam Combiner (Cont…)

9:01because okay we are getting a power loss

9:05but i was only expecting 30 watts to

9:08start with

9:08we had to have 38 watts average power

9:13okay which is a lot more than i was

9:16expecting to see

9:18and we’ve only got 1.4 watts loss right

9:21let’s turn that noise off

9:23i’m gonna have to deal with that in some

9:24way later but um let’s just live with it

9:27for the moment

9:30so yeah six millimeters

9:3310 millimeters

9:37and seven and a half millimeters now

9:40six is a very nice number because that’s

9:42the sort of number that i would expect

9:44to see

9:45out of a glass tube laser

9:48so we’re definitely going to go with the

9:51times two

9:54now i just spotted something rather

9:55strange and interesting


9:58which we should have to go back and

9:59check that there

10:01was with the beam combiner on

10:06this here is with the beam combiner on

10:11that doesn’t make sense we can’t have


10:15because we’ve gone further away i was

10:18expecting a loss

10:19further away so i’ve actually taken the

10:22wrong two numbers here

10:28okay so this stability and warm-up thing

10:32seems to have some truth in it because

10:35when i re-run the numbers i’m getting

10:3737.6 watts

10:40when i move away 1.3 meters with the

10:43beam combiner on

10:46i’m getting 38 watts so i’m still

10:49getting more watts close up

10:51than i am when i’m 1.3 meters away now

10:54that sounds like a miracle

10:56but in fact i think it’s probably just

10:58the system is not capable

11:00of resolving to these 0.1 of a watt or

11:03something like so we’re losing 7

11:05because of the beam combiner and nothing

11:08because of distance which is brilliant

11:10news some reason or other

11:14we seem to have a 40 watt unit almost

11:18i don’t know but it turns out this unit

11:20might be

11:2140 watts um there is no external

11:25difference between a 30 watt and a 40

11:27watt unit

11:28and the paperwork definitely said this

11:31was a 30 watt unit but i’ve

11:32got half an idea that that was cloud ray

11:36devaluing the unit for customs purposes


11:39the 40 watt is about 400 more

11:43so yeah they’ve saved quite a lot on

11:45duty by doing that

11:47but anyway we’re going to put this back

11:49together now that we’ve

11:50checked everything out i’m going to

11:52assemble the mirror and then we’ll go

11:54through the setup procedure i’ll set the

11:56beam up

11:56i’m going to go and set up my y-axis now

12:00um i’ve got the beam approximately

Transcript for Let’s See What We Have – Beam Combiner (Cont…)

12:03through the hole i’ve already had this

12:04machine set up and the y-axis once so it

12:06shouldn’t be too far out but normally

12:10this would be

12:11several stages to get this right but i

12:14don’t know how many is it’s going to

12:15take me let’s just have a go

12:21see what the second one is like

12:26it’s not bad it’s a little bit to the

12:28left isn’t it

12:29probably just to show too far so because

12:31it’s so close we should have to do it

12:32again you can always use the back of the


12:36because we’re not trying to get it on

12:37center we’re just trying to get two dots

12:39that coincide

12:40so let’s just make a target

12:43and we’ll see how close we can get with

12:44this one

12:48spot on so that was a couple of goes

12:52within getting wide but hey this is a

12:54bit abnormal because i wouldn’t normally

12:56have the machine

12:57set this way design some special targets

12:59for the mark ii head because there are

13:00one or two oddities about the head

13:02that we need to take into account so

13:06the first thing that i’ve done is

13:07manufactured a target like this if these

13:09fixing screws appear to be

13:11too long well they’re not too long

13:13they’re designed

13:15so that you can plug a target onto them

13:17like that

13:23and then at the other end of the stroke

13:24where we’ve got a little bit more light

13:27not bad just a little tweak to the right

13:31now this is where you just can’t get

13:33your fingers in there

13:34to adjust these screws and this is where

13:37you now need

13:38the access panel it’s on the side here

13:45now just about spot on it just so

13:47happened it was in the center of the


13:50but that does not mean to say that it’s

13:53in the right place so we can use the

13:54back of that target

13:57on the table we can fire a spot down

13:59onto that target

14:03then we can drop the table down this is

14:05very very very slow this machine

14:08there we go three or four inches now

14:11we’ll check again

14:15and we’re out

14:26looks pretty good but hey we’ve got to

14:29do all that again now

14:30as i’ve warned you previously

14:34although we’ve got this thing set up

14:35mechanically square

14:37you need to just check to make

14:39absolutely sure that it is

14:42sitting upright and square so this is

14:45set up right in both axes and now we do

14:47it again

14:49there we go now that’s a nice round spot

14:51i have to say

14:53and it’s also nice and small

14:58remember we’ve had one attempt it

15:00probably is going to take three attempts

Transcript for Let’s See What We Have – Beam Combiner (Cont…)

15:02to get this set

15:04so it’s a very laborious process when

15:06you’ve got a slow table like this

15:09second pulse

15:12is out so we need to bring it


15:25more a little bit more

15:32a bit more

15:37pretty well there now we’ve got to come

15:38forward a shade

15:43just a shade more

15:50too much

15:55that’s pretty good we’ve got another

15:56target here

15:58which is square and it’s got a little


16:02where you tear it off that tab needs to

16:04be to this

16:05outside edge but there’s a hole in there


16:08make sure you put a hole in that corner

16:13and that’s the center that we’re looking

16:16for where we bounce off this mirror

16:19so let’s see how good we are for the

16:21center of the lens now

16:24not bad actually

16:28so we’re pretty good that way

16:32so we haven’t got to raise or lower the

16:34mirror what we’ve got to do is just

16:35bring it slightly this way

16:37with the y-axis adjustment which is over

16:40on mirror

16:41number two so just loosen mirror two off

16:45and it’s gonna come across what maybe

16:47three millimeters a quick pulse

16:52too much see if i can leave it loose

16:56there we go just about spot on and

16:58that’s how easy it is to set up wide

17:00we’ll just check it now that i’ve

17:01tightened it back up

17:04there we go so our beam is now passing

17:07right down the central axis of the lens

17:08and we’re going to get an upright

17:09and the final check i like to perform

17:15you’ve got to look at it at just the

17:17right angle because the light is wrong

17:20it’s not far off the center as you can

17:22see i’m pretty pleased with that for a

17:23set up

17:24now i said i wasn’t going to play with

17:26this machine

17:27until i’ve got it and understood it a

17:29bit more but

17:31i’m so fascinated by the size of that

17:33dot that

17:34i’m actually going to run a very quick

17:36dot test on here at 400 millimeters a

17:38second and 25

17:40power just to see what we’ve got origin

17:44and off we go

17:48obviously haven’t set the accelerations

17:50up yet i would say that they’re probably

17:52about 0.15

17:54dots that i can see on there

17:57they’re not they’re not 0.1 dots but


Transcript for Let’s See What We Have – Beam Combiner (Cont…)

18:01they’re certainly all separated

18:04which for a two inch lens is pretty good


18:07and that bodes quite well

18:10now i don’t want you to laugh but in an

18:13attempt to quiet this thing down

18:15i have modified the back panel

18:19so that it allows air in and i put an

18:21upward deflector on it to catch the


18:24maybe it will deflect the sound


18:27let’s see how this works

18:32right this is make it any quieter

18:42a little bit

18:46take some of the high frequency away and

18:48certainly for the front of the machine

18:50here it doesn’t sound too bad at all

18:52i could live with this i think the

18:54extraction is now going to be louder

18:57than the rf we don’t need that noise do


19:06it’s still annoying isn’t it um but

19:10hey i’ll leave it like that for a little

19:11while oh by the way um

19:13don’t worry there is plenty of air

19:16coming at the end here

19:17i’ve got uh i’ve taken the end panel off

19:19so all my air is exhausting at this end

19:22well this has actually been quite a

19:24successful session we’ve managed to

19:25establish that we’ve got

19:27a good beam we’ve got no loss of power

19:32and we’ve set the machine up pretty


19:36we’ve seen the potential for getting

19:39very small dots

19:40at high speed and we haven’t even tried

19:43to set the machine to do it at the

19:45moment it’s doing it on its own

19:47so lots of promise

19:50but we’ve got lots of laborious things

19:53to explore and check out

19:55before we really get into the depths of

19:57this machine

19:58how does the rf tube actually work i’m

20:01about 80

20:03of the way to understanding how that


20:06and it’s been a difficult process


20:09there’s not much out there telling me

20:11how it works thank you very much for

20:13your time again

20:14and i’ll catch up with you in the next


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