Violet LD Spectral Tests...415nm+ from BDR 209!

Hey everybody! Recently I spec'd out a bunch of diodes for a project in the lab I work in, and I felt like you guys might find it interesting! Two out of the 6 BDR diodes I tested were over 415nm...crazy!

Results were taken on a recently calibrated Ocean Optics High Resolution spectrometer.


"405nm" diodes from a BDR-209 sled, drive current = 500mA

Diode # lambda max

1 410.130nm
2 416.136nm
3 408.716nm
4 410.312nm
5 412.310nm
6 415.194nm

We hit >415nm with two of the diodes...pretty amazing! One thing to note is that the spectra of these diodes was actually kind of messy...not Gaussian. The average wavelength is probably about 0.5nm less than the lambda max values.


"405nm" diodes from 12X blu-ray burner optical sled (SO6J), drive current = 500mA

Diode # lambda max

1 411.494nm
2 408.853nm


Osram PL450B blue laser diode, drive current = 140mA

Diode # lambda max

1 447.574nm
2 447.855nm
3 447.372nm


So this is pretty awesome for those interested in high WL blu-ray lasers, but it is kinda bad for my future project of diode pumping a ruby...

Hi S,
Awesome testing impressive greatWL from 405 to 416+.Great thread pal interesting data.I have a few in these WL's and just love them. Can't get enough of them.Good job on the thread. Should get off the ground no problem
Oh another dye i'm fond of is the PLTB450B I 'll take it over a M140 anyway of the week hands down..

Rich

Pretty cool, can you see the difference in wavelength?

I'm quite surprised by the variability in the BDR209 set.

Did you ensure indentical heatsinking in all of them, i.e. were these readings produces at an identical die temperature for all of them?

If so it might be interesting to cherry pick. You'd probably not notice any difference in wavelength unless viewed side by side, but you might in apparent brightness - similar to what happens at the red end of the spectrum the other way around.

Honestly this was not a very controlled setup. Even though we have all the equipment for very tight thermal and current regulation, I just wanted to do a quick test on them all. They were all in aixiz modules sandwiched in a vise...and ran for 30sec before taking the spectrum.

I see. The differences in the 209 units would not be explained away for thermal reasons though, even if there was a difference in temperature of 10K between tests.

It's interesting that all of them were well over 405 nm - possibly because you're driving them pretty hard, but still. Considering the cost of these sleds and the chances of getting a diode that's closer to 415 than 405 it sparks my interest, especially since these are powerful single mode.

Obviously the visibility of the beam even at 415 nm is marginal compared to 445. For a close range laser show they wouldn't do that much, but at a distance they could give the 445 multimodes a run for their money.

Thanks for sharing the results. It's interesting that not one of the 405nm was actually 405nm, lol! Do you have any plans to spec other wavelengths and diodes?

Benm said:

I see. The differences in the 209 units would not be explained away for thermal reasons though, even if there was a difference in temperature of 10K between tests.

It's interesting that all of them were well over 405 nm - possibly because you're driving them pretty hard, but still. Considering the cost of these sleds and the chances of getting a diode that's closer to 415 than 405 it sparks my interest, especially since these are powerful single mode.

Obviously the visibility of the beam even at 415 nm is marginal compared to 445. For a close range laser show they wouldn't do that much, but at a distance they could give the 445 multimodes a run for their money.

Click to expand...

Yeah I found it very surprising how far away from 405nm these were. They were being driven hard but I would have thought it would be important for these to be near their rated wavelength for use in optical drives. Standard deviation was 3.0nm for the set, compared to 0.24nm for the Osram diodes (which were driven much softer for the record). The funny thing is those Osram diodes are mainly used in display applications, so the wavelength shouldn't matter much!

olympus mons said:

Thanks for sharing the results. It's interesting that not one of the 405nm was actually 405nm, lol! Do you have any plans to spec other wavelengths and diodes?

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Yes there will likely be more diodes spec'd out in the future. The lab I'm working in is looking into building an external cavity around some of the more common single mode diodes, forcing them to lase at even higher wavelengths (maybe even 425nm+).

For the performance in optical drive systems the tolerances are pretty wide actually. As a measure of thumb the error in a system can be as large as 1/10th of the wavelength. I'm not sure this directly applies here, but that would mean that the distance between optical features on the disc could be in the 365-445 nm range for a 405 nm system, keeping it working as intended.

Back in the day this was used/abused to some extent to increase the capacity of audio cd's: running the tracks closer together than specified, and also decreasing the pitch a bit, resulted in discs that could play for close to 80 minutes where the original spec allowed only 73 or so.

None of this explains why these are consistently at a longer wavelength tough.

I wonder if these were from similar batches that just were on the long side of the spectrum, it was due to high current, or it is a general property of 405 nm high power laser diodes. If you get the chance, it might be nice to re-test these things at say 200 mA or so, and also measure the temperature if by any means possible.

styropyro said:

They were all in aixiz modules sandwiched in a vise...and ran for 30sec before taking the spectrum.

Click to expand...

Can your spectrometer measure or just show laser spectra after 5 s, 10 s, 20 s, and 30 s switching on? You would see how spectra redshift.

Good news mate I love this wavelength and I had a feeling the 16x are brighter and more visible, if only they weren't so sensitive, oh and 500ma isn't pushing them hard, I would think 0.5a is a reasonable current considering everyone pushes them much higher. I've been waiting for someone to spectro this diode great job mate.