chapter  30
24 Pages

Laser Diode and Laser Diode-Based Lighting

LEDs work by spontaneous emission in which an electron annihilates a hole releasing a photon. Here, the carriers recombine with an average lifetime but not with any specic lifetime indentured to a particular carrier. Electron-hole recombination, and therefore photon emission, takes place even after the withdrawal of bias voltage. Also, this photon emission occurs at a rate which is independent of any external perturbing electromagnetic

radiation. Moreover, the photons emitted in this process have many dierent wavelengths and ramble in random directions; hence, they are incoherent or disjointed. Such emission is essentially an unprompted or voluntary emission; hence termed “spontaneous.”