Any ideas what wavelength from this sled?

[hammong]

Hello all - My first post here after lurking a while.

I'm a laser enthusiast from way back, having owned a 10mw HeNe 20 years ago, rebuilt a Argon-Ion blue laser power supply and optics from scratch, and I got a nice Synrad 10W CO2 project in the basement.

I've recently started fiddling around with diode lasers, mostly because I wanted to see if I could get a hand-held burner together.

So, I have this LG GBC-H20L Blu-ray reader, 16X DVD-RW, LightScribe burner that I've been having some Windows 7 compatibility issues with. I decided to scrap the thing, and replace it with something less problematic. I took the cover off, the main logic board, and exposed the sled -- and it didn't look like any of the other sleds i've seen posted here or elsewhere. So, I'm sort of guessing what might be in it. The "left" diode was definitely 405nm. I figured the "middle" one was the DVD-RW burner because it seemed to have the most metal sinking around it in the sled. The right one? I guess it's the CD-RW.

I mounted the "middle" diode in a new Aixiz plastic lens module, built a LM317 driver, and set it for 200 mA and it lazed stable for 5 minutes with no current-rise, so I bumped it up to 220 mA, then 240 mA. At 240mA, the current started to creep up due to heat loading, so I backed it down again to 220 mA.

At 220 mA, it will readily burn any dark colored organic or plastic material (wood, paper, electrical tape, etc).

My question is this... Despite the high output, the "apparant brightness" of the beam is substantially LESS than my cheap 1mW red bullet pointer from the drug store. I'm guessing the 1mW pointer is 650-670nm by the color. Definitely red, not red-orange 635nm.

Do you think I mounted the CD-RW diode by mistake? Aren't they 780-808nm or so, and should be mostly invisible? If it's the DVD diode, wouldn't it appear brighter?


I've attached a picture of the sled with some indications of where the 3 diodes were. The "DVD?" in the middle is the one I have mounted now, the left one is definitely the 405nm (confirmed tested).

Greg

 

[Wolfman29]

Just from your description, I would say that it's the IR one. They are usually 780nm, which is at the very edges of human vision. The reason you can see it, however, is that it's ridiculously powerful (my guess is around 180mW at that current). So... I would be careful! Your eyes aren't reacting as strongly as they would, so it seems dimmer... but it's really just as dangerous!

 

[Kookapeli]

I'd go with the IR too, if it was the 650nm one you'd definitely see it properly !

 

[foulmist]

take a picture/video of it while running .. the IR light would appear more pink than red (and on camera it appears way more bright) also was it open can? or closed can? the LG's are using open can diodes for red ... at least the ones I got dismantled

 

[hammong]

I pulled the remaining diode out of the sled and swapped it into my module, and this last one is definitely the DVD 650nm diode. It's bright red, "visual" brightness difference between it and the 780nm (?) CDRW diode is at least twenty to fifty times as bright at the same current draw. The maximum current my driver will deliver is 245 mA and the 650nm diode seems to be quite stable and not producing much case heat. Looks like I got a winner so far!

Any recommendations for drive current for my blu-ray 405nm reader diode out of the sled? I'm waiting on my Aixiz module to arrive before I put it together, but I did test fire it at 30 mA and it's really pretty. =)

To answer question about the diodes, the 650nm from the sled is a longer closed can, the 780nm and 405nm are shorter closed cans. Both of the red diodes have a surface mount window on the front of the can.

I damaged the 780nm front window slightly when I extracted it from the module, but to be honest, I'm more fearful of the IR/near-IR diodes because I can't see the reflections or the primary spot that well. No big loss to me.

Greg

 

[Bionic-Badger]

30mA might be about as much as you should put through that 405nm one you have if it's just a reader. The old ones we used to use were reaaaally touchy about larger amounts of current, and would die with more than about 30mA.

 

[hammong]

Well, I've gotten back to the 405nm diode from this sled, and gave it a good workout today. The threshold current was 28mA, and I'm currently running it at 65mA. I don't want to press it any further, but it seems stable and I've got it mounted in a project case with my homemade DDL driver.

Thanks for all the responses to the thread. This little 405 is so pretty, makes me want to order a higher power diode and ramp it up a bit. =)

Greg