Strange shaped blue ray beam

I tried to get a photo of this but my camera cannot see past the bright spot. my picture is as accurate a drawing as I could do of the spot, is this to be expected armed with the following information?

The driver on my blue ray is set up for 7.2v 45ma, I am still waiting for my RCR123 cells so I am running it @6v at the moment. This means it is on the edge of laseing and this beam shape may clear up with the correct power input.

Regards rog8811

*Edit...typo in picture corrected :-[

Yes, that looks about right. A bare diode like that will emit at a wide angle in one direction, but not so wide in the other. That means if you just stick a lens in front of it, you'll get that more intense stripe in the middle. The other oddities are because of the poor mode characteristics of the diode.

Something is sounding fishy here though, you say you're giving it 7.2V and 45mA and its underdriven? At 7.2V it would probably be drawing hundreds of mA so I'm guessing the voltage figure is off? And at 45mA its not underdriven - you're bordering on the edge of overdriving. Overdriving it could also produce weird effects! (one such effect being the infamous "black laser beam")

Did you say no Lens in front of the LD ?? If you have one, plastic, that could be flourescence. Mine has a little but very little.

Mike

@ Pseudo, sorry did not give quite enough info.... This is regulated with a 7805 which has an overhead of 1.7v so with the 6v (2 X CR123A's) I am running at the moment the voltage at the LD is a max of 4.3v which is on the edge of the drive voltage required.

@ Mike, it does have an Aixiz lens in place. I know you have done a lot of experimentation on these blue rays already, does this flourescence get better as the power to the LD is increased?

I did set this up using 7.2v but I did not look to see if the spot looked good as I was holding everything in place and wanted to get it safely into the housing before I shorted something out.

Regards rog8811

How very odd Rog. On extended running with my blu ray module last night, my diode started to produce something very similar to what you describe. the violet bar became very distorted and mine actually produced a big yellow block below the main lasing spot. At first I thought the diode was dying, but I am only running it at 5.1v drawing 37ma. I could actually see a yellow fan coming off the main beam in fog. I upped the current limiter on my psu to 42ma and the artifact disappeared. I reset to 37ma, but have not been able to reproduce the effect, maybe it is a heat issue.

Jase

Mine did something like this too, there was some yellow light coming out, someone told me that was a failure mode, this was just before I blew the pot. :'(

If I hold my pointer close to a grey surface I can still pick out the yellow rectangle but at any distance it does not effect the spot, with mine it was all down to voltage..Jase, I will have to try fogging mine to see if it is evident....
@shikari_rock, did blowing the pot blow your LD too?

Regards rog8811

I think you are just seeing some internal reflections. I get pretty well the same. Here are a couple of pics of mine.





Paul

rog8811 said:

@shikari_rock, did blowing the pot blow your LD too?

Click to expand...

Unfortunately yes...
Now I have a body in my drawer...