We report the use of fluence-dependent self-defocusing nonlinear absorption and laser-induced melting and subsequent crystalline regrowth (annealing) in silicon to construct a passive nonlinear optical energy switch. The device has high transmission for low input energies but low transmission for high input energies. The optical self-action mechanisms responsible for the switching have a subpicosecond initiation time and a recovery time determined by the carrier lifetime, which can be adjusted from nearly a millisecond for very pure crystalline Si to <5 psec for severely radiation-damaged Si. In contrast to previous power-restricting nonlinear optical switches1–3 using organic liquids, this device offers the advantage of isolating energy components from pulses that exceed some critical energy for all pulse widths less than the carrier lifetime. Other possible applications of this device include its use as an optical Zener diode in integrated optical circuits.
© 1984 Optical Society of AmericaPDF Article