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Thread: 635nm Laser diodes

  1. #1
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    Default 635nm Laser diodes

    Hey guys,

    I asked this question to Marconi in a PM, but I'll now ask you guys too.

    Has anybody came accross decent powered (100-200mw) 635nm laser diodes with reasonably sized apertures ? (less than 60um stripe) ....

    I've seen the roithner 100mws... but was looking more at 200mw if possible.

    Don't they use 635nm in dual layer dvd burners ?

    Cheers,

    aijii-
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  2. #2
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    Aijii
    I am just in the process of combining 2 diodes from DL dvd burners & they are deffo not 635nm. I think all dvd is 658nm - no reason to have 2 wavelengths - unfortnately for us.
    I am getting 200mW each (at a shade over 300mA) but obviously we need a lot of power due to the colour

    Rob

  3. #3

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    Quote Originally Posted by stanwax View Post
    I am getting 200mW each (at a shade over 300mA)
    At what wavelength? How are you measuring them? How long do they last with that drive current? Also, what write speed were the drives specified for?

    Aijii, I think DVD diodes would be single mode types only. I don't think any single mode 635 nm diode exists beyond 45 or 50 mW. I haven't seen a 200 mW multimode type either. Not really looked though, I'm interested in 650 nm or so, but 635 nm isn't a colour I like very much.

  4. #4
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    Doc
    I'm measuring using laser check set to 658nm - so cant be certain of wavelength or reading accuracy (but hopefully in the ball park)

    as for life...i have kill quite a few of these but to date I havent killed one in action so to speak. they have died due to other reasons - static, power supply spikes, robs stupidity etc.

    As me again in a week - hopefully the twin diode set up will be operational tonight so I will start the real burn in.

    I have traditionally used lite-on drives the latest with the open diode are rated at x20 model number LH-20A though I did just buy 2 Pioneer DVR 112D which are rated at x18 and appear to use the same open diode.

    Rob

  5. #5

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    Sounds cool.
    I'm cautious about the wavelength because it can be wrong. Mine was. I assumed 658 nm too, and thought my thermopile meter project was borked, hence my total dismissal of my part in that in Hemlock Mike's thread. I later repented (a bit) but didn't add to the thread, as I'm still not willing to formally claim anything I can't back up. That said, I'm fairly certain that my meter idea is valid, I just didn't like what it told me. It said my Rohm diodes, set at a conservative 140 mW, were actually only putting out 121 mW! I eventually decided to assume it was truthful, and to see why the Lasercheck was saying different, if it wasn't lying. (Initial (depressing) assumption was that ether meter, or even both, lied. Everything lies. ) So, I assumed instead, 121 mW was true, then set the Lasercheck to the wavelength that matched that power reading. It was 664 nm, which just happens to be the lower limit in the specs for the Rohm diodes. Coincidence? I think not. It's the only way both meters can be telling the truth.

    A difference of just 6 nm can make a difference between readings of 120 mW and 140 mW, so a Lasercheck is a deeply suspect device for trusting as sole measure of a laser diode output. If we all choose 665 nm as the wavelength for measuring a DVD diode we'll be closer to the truth. If it's running hot, set for 670 nm. (Mine were running at less than blood heat, yet were still as longwave as 664 nm, so when hot, they'll be longer wave than the makers admit to as a maximum) The readings might be less exciting, but any surprises we find will be good ones.

  6. #6
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    interesting stuff...I do know how sus the lasercheck is or rather how sensitive it is to wavelength - hence the crazy readings from dpss weven witha small amount of ir leakage - so ultimately cant trust it for a diode and of course the biggest drawback of the DVD drive as the source is that you cant get specs. I would love to know if im on the edge of LD death or if there is still 50mA margin I could squeeze. Its just a matter of being brave - or caring how much you spend on dvds.

    Rob

  7. #7

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    a source for 200mw 650nm diodes wold be very good
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  8. #8

  9. #9

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    Quote Originally Posted by andy_con View Post
    a source for 200mw 650nm diodes wold be very good
    True. But, to unhijack Aijii's thread, and revert to what might be the most interesting line of inquiry, what high power multimode diodes exist with stripe widths of less than 100 µm? I know that Roithner and Intelite sometimes have things of interest, but they're rare, and expensive. Narrow-stripe multimodes are VERY interesting, and by far the best way we'll easily get more power. Works for Marconi.... If a few of us start looking closely for these things, we might unearth something we can get at.

    Rob, I'm not sure how good a guide it is, but on Opnext diodes it was possible to see the margin by eye. The coherence would fall off, the speckle would lose its sparkle and become like a pastel shade (probably due to a linewidth broadening similar to the effect of too much feedback gain in an analog audio filter oscillation making it noisy). It's not obvious, it takes some practise to spot it, and the beam is best projected at a very shallow angle onto a matt black surface to see it, but I used it as a guide to current limits. It safely allowed me within 10 mA of serious diode risk, while still allowing thousands of hours life. It was an ideal test. The problem is, it doesn't seem to apply to the Rohm diodes, nor did it apply to the diode Pit8ull sent to me for testing. The lifetime of those diodes is a lot reduced before anything like that effect becomes visible. With those, I think early death by retroreflection off a Lasercheck ND filter is a better guide, but it's not an ideal test, obviously...

    Edit: Andy, I bet those are 100 µm types. To get that much power, they'd have to be, probably. Those diodes, overdriven, are good candidates to explain the laser discussed in this thread.
    Last edited by The_Doctor; 05-03-2007 at 12:55.

  10. #10
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    Hey guys,

    Found these ages ago... 60um stripe width... @ 635nm 300mw....

    http://rpmclasers.com/products_622-700.htm

    60um doesn't sound too bad at all .. any ideas on what sort of divergence/beam size would be attainable with this ?

    RPMC can also put a microlens in front of the aperture to slow the fast axis divergence down somewhat...

    They have these available in a range of casings.... but are $$ in single quantities.
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