Everyone certainly knows laser pointers. You can have a lot of fun with them.
On the other hand the pointer only shines, has no thermal effect. Not surprisingly, when
its optical power is only around 1 mW (maximal 5mW). I wanted to make a laser with higher power output,
but the construction of classical laser is very difficult, so maybe sometimes...
Recently I came across 3 broken CD-RW burners. Lasers in these drives tend to have a pulse output of about 100 - 250mW and continuous power 50 - 125mW and work in the infrared range at a wavelength of 780nm. Average operating current is about 100 to 150 mA, pulse up to 200mA. I used a supply of 100mA (it would be possible to use more, but there is a risk of destruction of diodes, because its type is difficult to identify). The voltage drop across the diode is about 2.1 - 2.15 V. As a current limiter I used simply a resistor. It's not ideal solution, but it works. Better would be a stabilised current supply with 7805 or LM317 (see here).
In the original construction of the laser unit, the laser beam is focused at the focal length of a few mm, which is not suitable for experiments. There are two lenses: the first transforms the divergent diode light into an parallel beam, the second focuses it to a near point. There are two possible solutions:
1) Remove the laser diode and place it into optics from another device (laser printer, metal pointer, ...). This is only possible with conventional housings 5.6 mm which fits into the optics.
2) Leave the laser diode in the the original unit, remove one of the lenses (the one closer to CD). The second lens is shifted a little bit away from the diode to make a beam focused to a focal point at a desired distance (1cm to 1m or more).
Laser diode must be placed exactly on the axis of the lens, otherwise you can not focus the beam. The laser diode should never be turned on if it is not placed in a sufficiently large metal cover - this serves as a heat sink!
What you can find in various drives:
- In DVD-RW drives there are 2 burning laser diodes: red for burning of DVD and infrared for burning of CD.
- The DVD-ROM drives (reading only) can only offer you a weak red diode like 1mW. they are good only to produce pointers or very faint laser-light show. They won't burn or cut anything.
- In the CD-RW / DVD-ROM combos (drive that burns CD and only reads DVD) you can find burning infrared diode and weak red diode (as in DVD-ROM)
- Finally, the diodes from CD-ROM readers are completely useless :).