- Apr 18, 2011
was surfing the net just now and came along this piece of info
source Sam's Laser FAQ - Items of InterestLaser Powered LEDs
If you have a green laser pointer or more powerful DPSS green (or shorter wavelength) laser, here's a very expensive way of lighting up a red LED. Get a green or yellow LED with a clear (not frosted) lens and connect it to a red LED anode-anode, cathode to cathode. With a bit of luck, if the green laser is shined directly into the green or yellow LED, the red LED will glow. How brightly will depend on many factors including the actual (not advertised!) power of your laser, how much of the beam spot hits the LED chip, and the specific characteristics of both LEDs.
Note that measuring the output voltage of the green or yellow LED with a multimeter will be inaccurate if your laser is pulsed or quasi-CW as it will read the average voltage which may be much lower than the forward voltage drop of the red LED. The peak power output of the LED will be proportional to the peak power of the incident laser beam. Thus, a pulsed laser is more likely to work here than a CW one. Your mileage may vary.
The principle behind this stunt is that the green or yellow LED acts like a solar cell (or should we say "laser cell") for the laser and generates an output which is a function of the incident optical power and its band-gap voltage. Shorter wavelength LEDs should be able to power longer wavelength LEDs but not the other way around (unless two are wired in series with two lasers used for optical input). Thus, it should be possible to power an IR LED from a red LED and HeNe laser but that would be so boring.
Don't expect rigs like this to be used an alternative power sources any time soon. The efficiency is less than a whopping 0.001 percent (electrical power of 0.5 W into the green DPSS laser for 1 microwatt or less optical output power from the red LED).