Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[planters]

Chilling is probably a little less valuable with these than with the LOCs as the increase in visibility from 635 to 620 is a little less steep. But, if these are Al GaAs diodes I suspect the delta T is probably similar. A larger C lens will not have a larger sweet spot as the FL defines the aberrations with a given beam diameter. There are no off axis aberrations with prisms, so if expanding several beam-lets at once why not use prisms? I wonder if the relative performance of the C-lens/prism may be explained by the difficulty in measuring very small differences in the near field beam dimensions. Also, a little residual miss focus in the initial collimator may be compensated by the cylinder, but not the prism and so it is important to revisit this when using prisms. Just a few thoughts.

[Solarfire]

I just did a few tests to see if it would be possible to knife edge these before the lava cylinder correction and the results are positive. The beams have to enter the first cylinder slightly angled towards the cylinder axis. The offset of each diode to the cylinder axis has to be pretty much equal yet as close to the axis as possible. The question remaining is, what will be the best divergence with a reasonable aperture beam size be. Testing was done with the Optima lens as collimator.

[andyf97]

I just did a few tests to see if it would be possible to knife edge these before the lava cylinder correction and the results are positive. The beams have to enter the first cylinder slightly angled towards the cylinder axis. The offset of each diode to the cylinder axis has to be pretty much equal yet as close to the axis as possible. The question remaining is, what will be the best divergence with a reasonable aperture beam size. Testing was done with the Optima lens as collimator.

I was wondering the same too but with the other unknown lens, what specs are the optima?

[mixedgas]

Just so you know, at least with some red diodes, superchilling cranks up the intracavity power density in the diode, and you have to drastically reduce the operating current, or they will explode, blowing the output face off the diode.

Says one who did the LN2 thing. I no longer have access to LN2. I have a friend who has seen it with stacked TECs, trying to get the wavelength down. I don't know about more modern dies, but 3 years ago it was a showstopper.

Single mode 650s did not like stacked TECs or LN2.

And it really did not crash the wavelength down that much. In fact, when I tested red leds, at some point when they got really cold the wavelength went the other way.

Controlled conditions, not with the LN2, I just plunged diodes into it with the power on.

Some superbright green leds just stopped conducting. Try chilling a 1990s Nichia green led with just dry ice, the conductivity goes WAY down and light output drastically falls off.

Steve

[Solarfire]

I was wondering the same too but with the other unknown lens, what specs are the optima?

fl = 4mm, NA = 0.5, a tested transmission >97% and a good price @ 17.90$ (just the lens)

[Stoney3K]

Just so you know, at least with some red diodes, superchilling cranks up the intracavity power density in the diode, and you have to drastically reduce the operating current, or they will explode, blowing the output face off the diode.

Says one who did the LN2 thing. I no longer have access to LN2. I have a friend who has seen it with stacked TECs, trying to get the wavelength down. I don't know about more modern dies, but 3 years ago it was a showstopper.

Single mode 650s did not like stacked TECs or LN2.

And it really did not crash the wavelength down that much. In fact, when I tested red leds, at some point when they got really cold the wavelength went the other way.

Controlled conditions, not with the LN2, I just plunged diodes into it with the power on.

Some superbright green leds just stopped conducting. Try chilling a 1990s Nichia green led with just dry ice, the conductivity goes WAY down and light output drastically falls off.

Steve

With these 638 diodes I'd even consider going the other way. If they are capable of running stable (and properly heat sinked) at a temperature of 50-60C, the wavelength would go up to somewhere around the 640-642 range. Which is right where we want it.

You might even kill two birds with 1 stone here since it's fairly easy to run the diode warmer than on the spec sheet - just by increasing operating current and therefore power. It's only a matter of finding the right balance there.

[badger1666]

has anyone on here tried one of these diodes ??

For $125 you can (or could) get Opnext HL6388mg which are 638 @ 250mW small emitter (20 um) . I've overdriven them to 500mA for an output of 350 mW after collimation lens.

[steve-o]

has anyone on here tried one of these diodes ??

Yes I have 2 , mounted, lensed and prismed, ready to go into my projector pending the results of this G71 testing. I ordered my Lava-lenses yesterday :]
The 6388s are much easier to tame.
I still have to figure if I want to knife-edge or PBS 'em. I popped a few , but found the problem was in my test setup. Now I have five 1N4007s across the DUT (diode under test )- (forward biased) to make sure that my "diode-tester" doesn't drain my wallet making LEDs out of LDs anymore. ehhhh. Those mitsus however did survive my abuse though, I have to say .sturdy little buggers ..

[CDBEAM]

SF...Good work !!! So....We can knife edge.....then thru a C-Lens pair !!! Great. A set up as in the pic....with all four (4) LD's slightly off-axis. Pics of your output beam ????? Thanx !

Beam

[Solarfire]

SF...Good work !!! So....We can knife edge.....then thru a C-Lens pair !!! Great. A set up as in the pic....with all four (4) LD's slightly off-axis. Pics of your output beam ????? Thanx !

Beam

I see you’re already planning with the G73s there.