My red laser stock was empty. Mainly due to my errors and experiments. As I didn’t find spare DVD recorders, I switched to infrared lasers (IR). It is much easier to find powerful IR laser- the source is any CDROM recorder. In newer high speed CDRW devices, lasers are quite powerful.
IR laser beam is invisible. Sometimes you can see so red light emitting from laser diode (do not stare to focused beam). It is not a miracle- you can’t see these wavelengths. It is just secondary LED emission near the cavity of the laser. Even if the laser part of the device is burn out, you can see this reddish light. Laser emission is very interesting phenomena- when we increase the current through the diode, we get LED light. As we increase current, suddenly optical generation starts – laser process is on. All low power and old lasers have photo-diode to detect this process and to measure optical power. New high power laser modules do not have photo-diodes installed, even the laser is in 3 pin package. You can notice, that third pin is not soldered to PCB. And if you disassemble laser itself, you can see, that there is not wire connected to this pin. Neither you can find photo diode. I wanted to get modern driver chip datasheets from elentec-intersil, but I received answer, that these documents are not for wide publication. Why? I don’t know. These chips are in every modern DVDRW device… So I can’t find how laser power is regulated in these devices.
I improved my power supply and started tests with lasers. Did I mentioned not to power high power laser diodes without coolers? So don’t.
To detect IR beam use any digital camera, USB camera or any other consumer device with CCD camera. CCD cameras’ have IR filter, but it is to weak to block laser beam.
This nice photo is made when I placed my digital camera lens to CDR recorder optics. As optics is untouched, we can see nice interference pattern. Just cool photo.