Line beam with Senkat's GB diode!?

[zerafiel]

Hi, I need some help with my GB diode. After I mounted it onto the aixiz housing and rigged it up for constant <100mA @ 3V to test the diode. I focused the lens and I get a nice tight line with a focused bright spot in the center.

Does anyone else have this problem? Is my diode defective? I know most red diodes have beams which are actually elliptical when unfocused but mine just gives a central spot with two bars at the side. When focused it becomes a line with a spot in the middle.

I tried to take a photo below but the central bright spot does not allow the line to be captured properly. The line is actually very fine when focused and longer than pictured. Slightly over 1 inch on each side at ~2m. my hand is shaky so the beamspot moved slightly.

It can't be the lens of the aixiz housing since it does not give this effect with the aixiz laser.
I don't think it is the lens of the diode either since i can't see any dirt on it.

If something is really blocking shouldn't I see a diffraction pattern instead of a line?

Any ideas what I should do or is my diode just bad. I read another thread about something blocking the emitter chip but it is too small to see anything clearly.

 

[zerafiel]

Oh, at the same focus at shorter range i get a nice circle and the lines aren't really visible. The spot is also larger. Line only appear at say over a 1-2m where my focus is.

 

[laserterd]

will it burn stuff right where its focused to a small dot? ive seen many pictures of problems like that before, but i dont know what people figured the problem was. when my handhelds look like that i take a lens cleaner and clean it out, and the dont is perfect again. it could be a scratch? might want to get senkats input here.

 

[Gazoo]

Recently discussed same problem:

http://www.laserpointerforums.com/forums/YaBB.pl?num=1187570730

 

[zerafiel]

just to clarify again. My beam looks nothing like the photo. It appears at a line with a dot. I am not going to test it for higher power when something is obviously wrong. Cleared the lens and results are the same. Don't think it is dirt as that will show up more as beam artifacts. Unlikely to be crack since the line is so well defined and symmetrical.

How do they actually turn dots into lines for laser modules? They have line generating optics with quite precise gratings or sth like that. Can't be that my lens fractures so nicely can it?
Puzzled.

I'm thinking something wrong at the emitter or at the diode lens

 

[Gazoo]

My open can diode does the same thing..I don't know why. I think it started when I pushed the current to 500ma's. But it has not effected anything else...it still burns just as good and the beam looks the same...so I am not worried about it.

If your line turns when you focus, it is the lens. If the line stays stationary, it is the diode.

 

[zerafiel]

Thanks for the link. I actually popped by that thread but only read about the 2 dots and the thing on the emitter. Reading further down. It seems LarryQ has the same problem as me.

But noone seems to know exactly what is causing it. Since the diode is closed and I don't have a centrifuging machine. It looks like there is nothing I can do about it except admire the saturn beam. Is knocking it around safe. How hard am I allowed to knock?

I am thinking it is light leaking from crack between the emitter chip and the substrate it rest on.
Hence the line and also the general elliptic shape of red diode lasers.

Kinda irritating but I will try it's burning capabilities soon.

 

[zerafiel]

It doesn't rotate when I focus or so I recall. Good point!

So it's the diode. Gah.

 

[Gazoo]

You said you ran it at 3 volts. At 3 volts it would be drawing much more current than 100ma's. At 2.5 volts it should draw around 130ma's, which is it's rated maximum CW power.

 

[zerafiel]

Ran it current limited not direct drive and at less than 100mA. 33ohm resistor + cap. About 90mA max.. measured around 80+mA

Besides don't people run this at 250mA or more CW??

I read someone runs it at 167mA CW for best stability and lifetime.

 

[Gazoo]

I have been posting that I think 160ma's is good for a longer life, and at 160ma's the diode is a very good burner. Going with high currents will dramatically shorten the life of the diodes, and may spell instant death, depending on the diode. Every diode has its own personality, some behave better than others.

 

[zerafiel]

Thought that might have been you as well. What voltage do you run it at? 2.5v or 3v?
Alright, I shall current limit at 150mA on the next burning test.

Gazoo, how much heat sinking do you use at 160mA CW? Is the aixiz module sufficient?

Another question is. The anode is connected to the diode case which is connected to the aixiz module. Do I need to 'float' the module if I do not want to keep touching the anode when the laser is running. Or is this perfectly fine? How do I isolate the anode and still heat sink it properly??

 

[Gazoo]

Well honestly I don't recall the voltage..currently I am only using my open can.

With 160ma's it took a while for my module to heat up and I have the really small Aixiz ones. Touch it once and a while to make sure it isn't getting hot.

These diodes have the cathode on the ground side...is that what you mean? You do not need to isolate it in a heatsink...

 

[zerafiel]

ah yes i meant cathode of the diode and anode of the battery. confusing sometimes since it goes by current flow instead of + and -

Just went to up the current slightly and boy did the brightness increase. The line disappears/gets overshadowed at high current I think. Was looking for something to burn and I found the perfect thing.

CHOCOLATE!

You guys have to try it. The fragrance of melting chocolate! OMG why do people burn plastic and poison their rooms when they can melt chocolate. Melted a 2mm by 2mm by 1.5 mm deep hole in a bar of chocolate. I thought it wasn't burning well but apparently the chocolates melts and becomes slightly reflective (careful) so it the power doesn't transmit very far beyond the surface. But when you dig past the shiny melted part you can see just how deep you went.

Everyone go try melting chocolate and tell me how fast you melt them!

 

[Gazoo]

If you want to poison your room try burning a floppy disk... ;D Or burning a hole through the black part of a CD/DVD case.

 

[zerafiel]

I upp the power again and wow my chocolate is smoking!! It burns faster and deeper thoughthe shielding effect is still present. Here are some pics of the poor chocolate bar.

Hard to capture the smoke but you can sort of see it.

Yes semi-expensive lindt dark choc!