Three types of electronic optical bistabilities in CdS

Abstract

We investigate optical bistability in CdS, induced by photo-electronic non-linearities. Varying the photon energy and the temperature of the sample we find three different types of optical bistability. The switching times are always around 1 ns or below, notably 300 PS for dispersive optical bistability. Optical bistability by bleaching of absorption at room temperature shows a contrast ratio of about 50 between the two stable branches. The dependence on various parameters, including the microscopic foundations, is discussed experimentally a s well as theoretically.

Light-induced transmission nonlinearities in gallium selenide

“…Such variations of the absorption coefficient and refractive index can be very large in the vicinity of the absorption edge and they are nonlinear because they do not depend directly on the incident beam intensity, but on some other variable which depends on it. These optical effects have been reported in cadmium sulfide ͑CdS͒ 11 and GaSe [12][13][14] and they are explained in terms of the screening of excitons by photogenerated carriers. The collision broadening of the free exciton resonance has also been claimed in order to explain changes in the absorption and refractive index in CdS and GaSe.…”

Tailoring light–matter coupling in semiconductor and hybrid-plasmonic nanowires

“…In testing the switch mechanism, the authors ruled out the dispersive, absorptive, and induced absorptive bistabilities previously shown by Wegener et al . in CdS platelets,[145] instead identifying the more recently discovered phenomenon of stimulated polariton-polariton scattering[146–148] as the most likely solution. First shown in larger microcavity structures, stimulated polariton scattering occurs when slowly decaying exciton-polaritons in the bottleneck regime at momentum k quickly scatter to a higher-momentum “idler” state at 2 k and a lower momentum “signal” state at k~ 0 in the presence of resonant excitation and an existing idler signal to stimulate scattering into the mode.…”

On the Multispike Structure of a Transmitted Pulse in Monocrystalline Films with Absorption Bistability

“…the absorption coefficicnt to zl.. and the diffusion coeflicient to YL'T-I . For bistability to take place, the absorption coefficient a ( N ) must, in the region of some N, change so sharply that [3] dcc CI G > N (3) Then, in this region (2) can have several steady-state solutions. The problem is to elucidate the conditions of a transition between these solutions.…”