Split Beam Problem

I am having a problem with a module I am experimenting with. It is a Lead Light 110, and it puts close to 500ma into the diode (too much I know).

The problem I have is that with the latest mod, the beam splits into 2 parallel beams, but it seems stable (to a madman). If I remove the mod the beam slowly returns to normal (both beams get dimmer then "snap" back to a single beam.

I belive that this behaviour is in the MCA, but is it simply because the crystal is being overdriven or is it a personailty of this particular MCA ?

I have not tried a realignment yet, whats your opinion ?

Gold

welcome to the wide world of mode hopping. TEM00 to TEM02

I get the same thing when I press down on the bore of one of the smaller HENE's here.

the crystal should not introduce hopping, sounds like the diode is freaking out in new and interesting ways.

Would love to see a video of this phenomenon.

i had a greenie(not a leadlight) that if i shook it, the beam would spawn a smaller offshoot. on that one i think it was crystal or optic misalignment.

OK Spec, today is not the best day but after a really bad day at work I had 20 minutes to set up and reproduce the splitting effect.

I have to appologise about the quality of the images, this weekend I am going to set up a high res camera with a controllerable shutter so I can get some "realistic shots". At the moment I am using i-Catcher CCTV software with a webcam.......

Now for some background, the module is a leadlight 110, with 2 resistor mods. I think we all have a module like this, about 3 months ago it died, and I put it in the bit bucket. Last week I hooked it up to a bench PSU and it came to life, I used it to to take images for my crystal mixing experimentation. If you follow lasermods experiences of the 110 you will note that he posted a correction to a resistor mod, well I ended up modding both the correct and incorrect components, this is when I thought the unit had died.

Following is resurection (NO not a Pheonix?) I tried Wyverns shot of the cap A106 this is when the beam splitting started.

This is a link to a shot video of a split/hop

http://www.rav89.dial.pipex.com/lasers/split.avi

If you download it it should play in media player.

I am also posting the following frames of a "hop"

http://www.rav89.dial.pipex.com/lasers/prehop.jpg

I am about to short the cap.

http://www.rav89.dial.pipex.com/lasers/posthop.jpg

After a short time the beam splits perfectly into 2 parallel beams

http://www.rav89.dial.pipex.com/lasers/posthop2.jpg

http://www.rav89.dial.pipex.com/lasers/posthop3.jpg

After the A106 cap short is removed the beam snaps back after about half a second. I was going to bin this unit but now the plan is to play with it more. I was going to put the latest mod on a toggle switch so I could easily add and remove these strange effects.

Whats it good for ?

How can I play with it ?

Gold

Wow...Free Effects :D

I want my laser to do that :?

Just kiddin Gold

Do you have your module "heatsinked" ?

May be temperature related...sounds like the diode is "Not Happy"

It does sit in a heatsink, BUT it has been running 24 hours a day for 3 days into a crystal (quartz varity). This said it is running at about 120ma and that only just gets it going.

To get the effects I set the voltage to 3.5 volts and short the cap, put on some pink floyd and relax. Once the beam has split the "dots" seems very....fluid, it (they) seems to change shape slightly in a liquid type fasion.

If I get the time to set up the new camera then I can get some decent shots this weekend. I will try and get a high frame rate avi to show the beam in detail, including looking towards the module.

Gold

3.5V is a bit hot for the circuit.

Looks like you are also introducing nasties in the form of ripples, the caps might simply be for eddy current/ripple protection to and from the diode.

Its a modern marvel that it is not completely dead...

Interesting "problem" you have there. I will take a video in a couple moments of my hene laser doing the exact same thing when I do the equivalent of "beating up the emitter"

gimme a little bit, hopefully I can get this to show up right.

i've also had this problem with a modded 105. after I did the diode alighnment mod(i already had a resistor mod) it started splitting. Mine starts out cold with 2 beams, then after 20 secs of warming up it snaps into 1, or if I just click the button again it snaps into 1.

as promised:

The "mode hop" video.

http://www.photonlexicon.com/hostedcontent/modehop.avi

It was recorded at 30fps, however I cut the frame rate to 15fps to slow it down so you could get an idea of the "liquid transitional period" involved.

the video started out at 30 megs raw mpeg but i managed to slap it into a 1.2meg xvid/divx file. there is enough grain in the video to annoy me, but it gets the point across.

Tell me what you think.

Hey Spec thanks for that, I love the perfection the the HeNe laser, that dot is spot on. That was a very good video and put mine to shame, but it was a web cam ! I will try and get another shot this weekend with a professional camera. My guess is that the best shot would be taken though a filter so the liquidity of the dot could be seen.

I know that this little module is suffering, it came back from the dead, but the more I play with it the more it gets interesting. I guess I now regard it as sacrifical.

Would it be safe to loose the driver board on this module and hook it up to a dedicated bench PSU (Thandar TS1452S), and control voltage and currect directly from the PSU ?

Spec, please excuse my ignorance but f the cap was to remove ripple surely it would sink it to ground, and if thats the case the short would short the power to the diode althogether ?

I have seem Modes TEM000 and TEM002 from this grennie, are there any others ?

Thanks for shareing your knowledge,

Regards

Gold

is there any way to fix this problem??

Yes...Replace the diode...
sorry to say I believe its damaged or flawed causing it to multi-mode, especially that much...
What you are seeing is it hopping between modes..those snaps back and forth...
When I test my diodes ..I use a photodetector and run it to an audio amp and listen to the beam ..tells many stories..if it is quiet..then there is no hopping..
Sometimes,..you can control it by finding the correct current to make it stop that and at the same time be at the right wavelength...most 808 diodes used are not multi-mode..they are single but every once in a while one will slip out of production flawed..Hard to see it being IR and all...
if they are you'de be seeing fat or multiple beams after conversion to green!!!

Reason I believe this is because I have run into this many times..and just changing the diode made it go away...

Also...mirror alignment , has a BIG play here too...
This will also cause that...sometimes when the crystal assembly is incorrectly aligned or mounted..causing the mirrors to be out of alignment to the diode and output optics.
The HR and AR mirrors are optically bonded or glued to the front and back surfaces of the Crystal assembly..so nothing you can do here...
You would havta crape the glue off and start over,..but thats a tedious job..and may damage the pump diode with execessive heat if not properly heatsinked or cooled.
I'd leave it alone and enjoy it...its a "special" greenie :D

Another thing to concider:

if a diode does turn out to be multimode the likely hood of it even appearing is very very slim in a pointer.

The KTP block in these systems is very small and has an even smaller "sweet spot" to produce green.

Either you have an EXTREMELY clean KTP block or you managed to find two exact spots in the crystal that allow the conversion to take place without the beam collapsing on itself or stopping mid-rock..

Congrats, Its like you won the lottery ;)

By the way I was mistaken about the mode your diode is producing.

Assuming there is no weak eliptical beam in the center of the two produced beams you have a TEM01 profile, if the eliptical beam is there its TEM02

Hi Spec

I am bringing home a much better camera this weekend so I will take some beam shots.

If the soldering holds up I am going to mount this module with a toggle switch to induce the multi mode. I will also see If I can get this behaviour at a lower voltage, I am extreamly reluctant to look at the optics, so I guess after a bit more play its destined for my personal museum.

By the way with 2 new C cells, I have observed the same results, so I know its not ripple from the PSU (it shouldnt be as its a good one.

I have got 2 new 110s here, which I am hoping to play with this weekend as well and I am going to mod one in exactly the same way just to confirm its a personaility of the optics, and not some side effect of the power mods.

Gold

Quote:

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Originally Posted by Spec

Another thing to concider:

if a diode does turn out to be multimode the likely hood of it even appearing is very very slim in a pointer.

The KTP block in these systems is very small and has an even smaller "sweet spot" to produce green.

Either you have an EXTREMELY clean KTP block or you managed to find two exact spots in the crystal that allow the conversion to take place without the beam collapsing on itself or stopping mid-rock..

Congrats, Its like you won the lottery ;)

By the way I was mistaken about the mode your diode is producing.

Assuming there is no weak eliptical beam in the center of the two produced beams you have a TEM01 profile, if the eliptical beam is there its TEM02

---

actually, sometimes my laser also has 3 elliptical dots, huddled very closly together with about the same brightness. Usually during warm-up it produces 2 dots and after a few seconds it snaps into a single perfectly circular dot. But ocassionally, when the battery has been drained a little, it will hit TEMo2, then jump between TEMo2 and o1, then snap into TEMoo, with the beam just barley making it out of the laser aperature.

Hi to all, this is my first post here although I like to surf and read here :)

2 or 3 split beam is easily fixed and I found it is caused by playing with the Diode (Aligning), the two pins going into the diode become loose and cause split beam either when hot or sometimes just always split. Also this has happened when the diode is over driven you get an immediate split beam -

1. Loosen lock ring as you would to adjust diode
2. Unscrew / remove front barrel (this will leave only diode + crystals etc)
3. Point to a white or light wall, you will now see 1, 2 or 3 huge fuzzy dots. Rotate diode until they come back together (this is usually quite quick and very easy to see because the green dots are very large).
4. Once you have just one dot of reasonable round shape then retighten the lock ring and all ok :wink: .
5. When you are happy with your beam, mix up some Araldite and put a drop right in amogst the 3 Diode Pins, This will stop them shifting again due to heat or movement.

Ive had 3 of my Modules do this while modding and all 3 are now perfect and pushing 30+ mw.

Hope this helps

andy

Welcome aboard Adyz... Glad to see you here... :D

Yep, sometimes this is just alignment. and easily cured..

Sometimes not..

If the facet gets damaged it is possible to correct it but at much less power.

I've prolly built over one hundred green modules and can say "it happens"

The stubburn ones ..you just have to replace the diode..

Anyhow, Glad that you have had good luck.

Also, I like the surefire laser mod you did... :)

You might want to check out this site.. It is in Japanese but he did one similar..

http://www1.ezbbs.net/09/sure-laser/

That was a few years ago, I wanted to do the same...but lack a lathe at the moment.

yours like very nice too... :D

*^_^*

:D Thanks for the link, I like his front engraved disc. I might look into getting some made up as it looks great. As for split beam yes I see your point, I have only just begun modding these Lasers and learning more as I go. I have a couple of heat related ideas which I will try when more modules arrive and If I get any improvement I will let you guys know.

andrew

Kewl Andyz..

Hey..Maybe you could make me one up..hehe

Maybe trade for one of our 100mw red modules.. :)

How much luck have you had with those 10mw infiniter modules from Jaycar?
I have tried to get an account with them to buy some things
But my efforts failed, I can login but cant put anything in my "basket".
I emailed them but nothing in return..
I guess they dont want my money!!!

Oh well... losta other fish in the sea!!!

*^_^*

Hi marconi, The Jaycars are not too happy when modded. I now only purchase Leadlights from the states and have had some great results, also much cheaper to purchase :wink:

Hi Andy

The split beam module now has a home as an oddity. Its mounted and has switch to activate the split beam mode. I like it, I have modded about 20 pointers now and this ones still special (its very efficient by the way).

I too liked your surefire mod, looks good.

Gold