Split Beam Problem

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

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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