Exciton–Phonon Mechanism of Optical Bistability

Abstract

PESTRYAKOV A joint effect of exciton-phonon and exciton-exciton interactions on optical properties of semiconductors is studied. In these substances the exciton density is shown to be a mukivalued function of incident light intensity and the frequency and temperature conditions under which the optical bistability arises are specified. Investigation of nonlinear optical properties of semicondudora with account for the indirect phototransitions exhibits that both multistable optical states and the bistable ones distinguished by a complicated dynamics of the switching may be observed in such systems.

10.1007/s11449-008-2011-z

“…Therefore, the relationship between the illumination (I 0 ) and transmission (I) intensities becomes nonlinear. As a result, certain intervals of external parameters may exist, within each of which two different values of I with correspond to one value of I 0 ; i.e., the state of optical bistability is implemented [8,9].…”

“…In the thermodynamic equilibrium state of the system of excitons, phonons, and laser radiation, the balance equation is satisfied as follows [9]:…”

“…Assuming the exciton concentration to be variable (via change in the illumination intensity I 0 ), one can find the absorption coefficient at fixed frequencies and temperatures from the system of equations (2), (3), (6)- (9), and the radiation intensity I at the output of a crystal of certain thickness d or the crystal transmittance τ = I/I 0 (as a function of I 0 ) from the Bouguer-Lambert law.…”

“…One of the causes of bistability in semiconductors is the dynamic nonlinearity of optical absorption in the exciton frequency range (internal optical bistability) [8,9]. The possibility of implementing two or more stable optical states of a crystal in the region of exciton resonances opens new possibilities not only for recording and storing optical information, but also for controlling the development of nonlinear phenomena by changing external factors.…”

“…Theoretical investigations of the manifestation of optical bistability in the region of excitation of Wannier-Mott and Frenkel excitons, carried out more than 15 years ago under the guidance of Nitsovich, nearly exhausted the problems related to manifestation of optical [9], temperature [10], polarization [11], and magnetooptical [12,13] bistabilities in isotropic crystals. It was established that the dynamic nonlinearity of optical absorption, which is favorable for implementing optical bistability at high laser intensities, is explained by the competition of the processes of excitation of exciton states and their relaxation due to the exciton-phonon interaction [13,14].…”