Broken 532nm DPSS Laser Pointer

Hi guys, I just registered to this interesting forum
I know that there is a similar thread just next to this but I'll open another since my problem is different: in my case the diode is working.

Anyway, starting from the beginning: some time ago I bought a cheap 5mw laser pointer on ebay. I used it for a while, then I modded it to increase the current and after a short time it stopped working. Ok, everything seems normal, I knew that this way the diode life will be dramatically shorten...

but it is not the diode who has died! it still works perfectly... it's the optics. Nothing exits from the optical group, no green light but no ir light as well.
The optical group should be composed only of 2 crystals and the collimating lens afaik... so i really can't understand, how can a piece of crystal be "burnt out"???


And also another question related to dpss: are crystals all the same or are they proportionate to the power of the diode? In other words, put the case that a 5mw green laser has a 25mw ir diode: if I take the crystals and use them with a 250mw ir diode would I have an output power near to 50mw or this is not the way it works?

Thanks

How do you know the diode is alive if you have no output from the aperture whatsoever?

I've dismantle it and tested with a camera sensible to IR light.

Yes but a little light is not LASING.....

With the crystals removed, you should still be able to project IR onto a wall.

The pointer in it's assembled state should still be able to emit a fair amount of IR; even if the crystals have failed.

so i really can't understand, how can a piece of crystal be "burnt out"???

Click to expand...

Crystals can burn out if energy applied exceeds the damage threshold of the crystal. You will generally see a burn spot.

photonaholic said:

Yes but a little light is not LASING.....

With the crystals removed, you should still be able to project IR onto a wall.

Click to expand...

yes, the IR spot is normal. Also comparing to another IR diode I have, the intensity is similar.

digital_blue said:

The pointer in it's assembled state should still be able to emit a fair amount of IR; even if the crystals have failed.

Click to expand...

I've tried several times but almost nothing exits from the optic group. Just a little bit of ir light that is visible only pointing the camera directly inside the output hole.

Crystals can burn out if energy applied exceeds the damage threshold of the crystal. You will generally see a burn spot.

Click to expand...

oh, that's interesting, so I'll try to open the optic group and access the crystals to check if I can see something strange.



So this is also the answer to my other question? Crystals must be proportioned to the diode power, so I cannot just change the diode with a more powerful one to get a more powerful laser?

Up to a point, yes, but the coatings on the crystal pump face will be ruined if the pump power exceeds a certain point. Typically, all pointer crystals between 5 and 100mW are the same dimensions and will accept between 200mW and 1W of pump energy. Your mileage may vary.

ElektroFreak said:

Up to a point, yes, but the coatings on the crystal pump face will be ruined if the pump power exceeds a certain point. Typically, all pointer crystals between 5 and 100mW are the same dimensions and will accept between 200mW and 1W of pump energy. Your mileage may vary.

Click to expand...

I've found this interesting link: DPM Crystals - Casix


I've also opened the optic group and what I've found is a cystal similar to those in the above link, ie nd:yvo4 and ktp coupled together:



at a visual analysis the crystal is ok: no burns or other strange things and it appears clear looking trough it.
But i'm trying to pump it with its original diode and with another 808nm (more powerful) diode that I have... and nothing seems to happen :s i really can't undersand...

The positioning has to be perfect. A long time ago, I was playing with a greenie that I got from Amazon.com, found that the crystal had to be perpendicular to the diode, but also rotated at just the right orientation. So try rotating it?

There is a thread in the green laser forum about DIY green dpss lasers, that ought to help you quite a bit, me-thinks.

yes, laser light from laser diodes is polarized so its angular position is important, I've tried several times in different poitions but nothing is emitted.

So I guess I need a new crystal group... thanks for your info about the DIY thread, I've paused the whole laser thing because i'm quite busy right now but when I've some time i'll look in that thread to see if someone has wrote where to buy those crystals at a resonable price

Use better batteries, then? You have a 2xAAA greenie, right? if you have a cr123 battery (3v, not the rechargable 3.7V), give that a try. I just lit my (advertised) 30mW greenie with a single 3.7V Li-Ion (measured at 3.77 resting) and it worked, but it was very bright, I am afraid of overpowering it. Using my freshest pair of AAA's, that are at 2.92V resting, the green doesn't even light, just an IR LED, pretty much.

Anyways, hope that helps. FYI, it was one of those generic 30mW kaleidoscope things that been popping up a lot everywhere.

In this kind of lower power dpss pointers, the diode is an open can diode very close to the crystal assembly. Coatings usually aren't the problem, it's the glue between the two crystals. Moving the crystals sideways will make the beam go past the burnt spot.
Or the diode died, best checked with a power meter.

Best source of these crystals? The cheapest would be a 5mw pointer. If somebody sells the crystals seperately, it's mostly tagged something like "200mW crystals!!" and sells for more than the pointer it came out of.