The best known of all opto-electronic devices is the so called LED (light-emitting diode), which emits a fairly narrow bandwidth of visible (usually red, orange, yellow or green) or invisible (infrared) light when its internal diode junction is stimulated by a forward electric current/voltage (power). LEDs have typical power-to-light energy conversion efficiencies some 10 to 50 times greater than of a simple tungsten lamp and have very...