current flow reverse if 'active'(LED)?

[system]

Heyah!

I searched for some information regarding LED's and found out that they can only go one way because of the two metals inside of the LED have 2+/- electrons making it easy to go one way but difficult to go the other way. This got me thinking about valves. When valves are open you can also squeeze to the other side! So I was wondering if it is possible to excite an LED(through a laser beam or something similar) to allow current to flow to the opposite "allowed" direction.

Setup:

+ = +
|<|= LED
- = -
--- = wire
LOAD=LOAD, I'm so clever. I know.

Laser beam shooting photons at LED
+ --- |<| --- LOAD --- -

I tried googling this kind of information but it appears that no one has really thought about it. Or I'm a bad googeler.

-Iskall

[CrossRoads]

http://arduino.cc/playground/Learning/LEDSensor

Try browsing for "led as photodetector arduino", will find some interesting hits.

[system]

That is very interesting and cool and all but sadly not what I'm looking for. I'm trying to create a cheap relay by having one diode connected to another diode, giving one diode some load and quite alot of power and then the other diode as a lever for the first diode for "on" / "off" with the big power source.

[CrossRoads]

Ah - that sounds like simple transistor.

PWM filter link
http://sim.okawa-denshi.jp/en/CRlowkeisan.htm