Optical Bistability in CdS and Related Materials

Optical Bistability at the Absorption Edge of Semiconductors

“…8) this is quite hopeless in the excitonic spectral range, because saturation of absorption is dominating in CdS a t T = 300 K. The exciton broadening is so large that off-resonant operation and, by this, increasing absorption can be achieved only far away from the resonance (Urbach tail) and at high intensities. Increasing absorption hysteresis observed on cooled CdS (T = 7 K) a t intensity levels of 1 kW/cm2 has been attributed t o OB via a collosional broadening of the free exciton [122]. But this explanation is in contradiction with current theoretical results 1202, 1981.…”

“…I n [113,120] closed hysteresis loops with sharp switch-on and -off have been observed a t intensities of 30 and 5 kW/cm2, respectively, consistent with the saturation intensity given before. I n [122] only switch-on has been found, but a t a much higher intensitiy of 1 MW/cm2. This is a result of the unreasonably long cavity length of 10 pm used.…”