Good source for the DVD diodes?

[p1t8ull]

Does that mean that a 635nm would look 3-4X as bright? -or the same brightness for 1/3 the output power?

Yup, or more. See http://repairfaq.ece.drexel.edu/sam/...io.htm#diodlm1 for a good explanation .

Pit.

[p1t8ull]

Does that mean that a 635nm would look 3-4X as bright? -or the same brightness for 1/3 the output power?

Yup, or more. See http://repairfaq.ece.drexel.edu/sam/...io.htm#diodlm1 for a good explanation on relative brightness.

Pit.

[steve-o]

Yeah I already found this on Sam's FAQ:
"Due to the sensitivity curve of the human eye, a wavelength of 635 nm appears at least 4 times brighter than an equivalent power level at 670 nm. Thus, shorter wavelength laser diodes will be best where maximum visibility is important."
Does anyone have a source for a good 635nm LD?

[steve-o]

Mmm 0.2 vs 0.06 That'd be like a 60mw 635nm= a 200 mw 660 in relative brightness. Now if the cost and beam quality were the same...
Thanks P1t for the reference.

Steve

[stanwax]

The chart I have (which i got from Medialas) is based upon a starting value for brightness of 1 at our peak sensitivity of 555nm. 635nm is shown as 0.217 658nm is 0.0687 670nm is 0.032.
This means we percieve 635nm as just over 3 times as bright as 658nm and a little over 6.5 times brighter than 670nm.
Incidentally 532nm is down as 0.88496 which means it appears almost 13 times as bright as 658nm!

Rob

[steve-o]

Does anyone have a good source for a couple of 30mw 635 diodes?
(or 1 60mw)? for cheep

[Hemlock Mike]

Doctor --
You mentioned somewhere here that you were building a power meter for higher power - thermopile or whatever. Where do you find plans for such sensors ?

Mike

[The_Doctor]

I worked it out after looking at one. I intend to publish some details here in a thread specially for this, as soon as I have mine built and working. Watch this (entirely virtual) space...

In other (sad) news, I regret to inform all ye present that the diode I was sent has gone the way of the Norwegian Blue and is now flying over pines and fjords in Valhalla.. (Post here.)
I'm recommending that they be run at a fraction over 200 mW after a lens, at a pinch, 200 mW after a PBS too, making two do 400 mW. If they can do this for over 1000 hours, preferably over 2000 hours, I'd consider them worthy.

[Hemlock Mike]

Doctor --

It doesn't appear that heat was responsible for the mortality. Any conjecture about the cause of failure ? Does "stuff" migrate in these causing them to trash ?? Maybe there's a watt-Hr rating !!!

Mike

[The_Doctor]

Agreed, not heat. At that current a Rohm diode would be putting out only around 120 mW, a value it should maintain for thousands of hours (I hope). There might be a difference in voltage drop but I doubt it, as this would change the heat dissipation. A heat difference between diode types would make a focus change in the lens in my modules, if there was enough of it. As the focus was perfect after changing from Rohm to Opnext, and stayed that way, that rules out heat.

I expected the retroreflection off the Lasercheck ND filter to be the first indicator of any weakness. That this didn't happen is something the Opnext diodes have in their favour. I don't know what the cause is though, but some kind of migration or erosion is going on. I noticed a slight scattering of light increasing slowly over the course of a day or so, either parallel or perpendicular to fast axis (not worked out which). It was like a vague extended lobe (not clean and sharp like that weird diagonal one). I think that damage sets in slowly on the facet, and eventually rises on a sharp exponential curve when it becomes enough to increase the energy density at the facet. I don't like that thought though, because I ought to be able to detect a slight fall-off in output power in the hours before collapse, and I didn't detect that. So I don't know.

If someone can shine one on a fast photodiode to datalog the noise leading up to a collapse, we might get a better idea.