Question about laser diode power

Peter Walsh wrote 08/07/2019 at 18:20 0 points

I'm considering a speed-of-light experiment using the diode from a cheap laser pointer to generate ns pulses of light using a transistor in avalanche mode.

The experiment would benefit from having powerful pulses, and the avalanche mode circuit allows me to choose the energy of each pulse by appropriate choice of capacitor.

I was wondering if there is any reason this wouldn't work, *assuming* the average power is within the laser diode spec, and *assuming* no other parameters are exceeded such as spark-gap distance or capacitor voltage rating.

For example, I am considering 12,000 pulses/sec at a peak power of 100 watts per ns pulse, which averages 1.2 mW, which is well within the 5mW rating of the diode with some safety overhead. (The avalanche voltage needed to generate pulses is around 180 volts, so 12,000 times a second a capacitor charged to 180 volts would dump energy into the laser diode.)

Is there any reason why this wouldn't work using cheap laser-pointer diodes?

(I need Red, Green, and Blue pulses to verify that the results aren't wavelength dependent).