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dp
02-26-2010, 11:36 AM
I recently replaced an older (3+ years old) ATA66 DVD burner in a new Linux server I'm building. The recent discussions of lasers and Evan's CNC laser prompted me to disassemble the old burner to see what could be found.

These things are full of fun stuff. I got two beam splitters, 3 lenses, two lasers, and two micro-motors. On tossing out the rest I decided to keep the two rods used as linear rails.

The lasers are tiny - I'd imagined them being larger, but that's not the case. Here's a typical package:

http://mfgcn.com/sitebuildercontent/sitebuilderpictures/5mwdiodespecweb.jpg

lazlo
02-26-2010, 12:12 PM
If you go over to the laser pointer forums, the current rage is to take apart Blu-Ray sleds, overdrive the blue laser diode, and build a 300 - 450mW laser. The sleds are surprisingly cheap, I don't know where the distributors are finding them:

http://www.youtube.com/v/DVugSGldXZ8&hl=en_US&fs=1&

dp
02-26-2010, 08:29 PM
If you go over to the laser pointer forums, the current rage is to take apart Blu-Ray sleds, overdrive the blue laser diode, and build a 300 - 450mW laser. The sleds are surprisingly cheap, I don't know where the distributors are finding them:



That's exactly what my sled looks like - no bluray laser, though. I think the power is above 100 mw and close to 400 mw pulsed. I'll have to burn one out to find out.

Evan
02-26-2010, 08:50 PM
The damage threshold is very sharply defined. At a certain optical power the exit facet is destroyed by the electric field. When that happens the laser turns into a low brightness LED if the driver circuit survives. Make sure the beam is not reflected back into the laser as that will either be seen by the regulator photodiode and used to clamp the output or the extra energy can help to destroy the laser crystal.

BTW, determining the ouput power is fairly easy. Once the chip begins to lase the power curve is very linear with increasing current. For most small red diode lasers the increase in power is very close to 1 milliwatt per milliamp of current beginning at the lasing threshold.

nheng
02-26-2010, 09:27 PM
The damage threshold is very sharply defined. At a certain optical power the exit facet is destroyed by the electric field. When that happens the laser turns into a low brightness LED if the driver circuit survives

A lot of newer laser die are more robust and this is not always the case anymore ... at least not before they put out several times their maximums.

I would also caution anyone working with NIR (i.e. 780nm from CD-R/RW units) wavelength lasers to protect their remaining eye. High power emissions will appear only as a dull red as if the laser is only in LED mode. Eye protection for the proper wavelength needs to be worn.

Den

lazlo
02-26-2010, 10:00 PM
I would also caution anyone working with NIR (i.e. 780nm from CD-R/RW units) wavelength lasers to protect their remaining eye. High power emissions will appear only as a dull red as if the laser is only in LED mode.

I have a 1 Watt 808nm (Infra-red) communication laser, and it's a little unnerving that you can't really see the beam. I have OD3 laser glasses -- I think they were $30.

Most of the high-power (20 - 40W) DPSS YAG lasers you can buy are infra-red. That's a lot of hassle to set up safely. Enclosed cabinets with power interlocks, and you really need a camera to view inside the enclosure, since even the slightest reflection will ruin your day.

dp
02-26-2010, 10:12 PM
An invisible laser beam is a bad neighbor. It's not something I have any interest in because of the hidden and real danger. Somewhere in my stack of stuff is a He-Ne laser. Until the power supply died it was a lot of fun but it's amazing how quickly a reflection will find your face. It's a 5 mw unit - definitely a nice piece of engineering. The case is threaded for various lenses.

Too bad it died. I was never able to resuscitate the supply. The vendor didn't have repair parts and didn't seem interested in repairing it. Odd given it was a lab quality laser.

I've a friend in BC that does laser work for a living and he's got the one good eye to prove it. His retina maps preclude his getting insurance coverage. You never see the one that gets you. He works with 30W lasers for etching objects. I'd be very uncomfortable being in the same room with that if the covers were off.