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Physical review. B, Condensed matter

New type of optical bistability in polymers mediated by phonons

Xiao-shen Li, D. L. Lin, Thomas F. George, Xin Sun

Published Feb 15, 1990• 20 citations
Publisher

Abstract

A new type of optical bistability mediated by phonon and virtual-exciton coupling is suggested for polymers. Numerical results with parameters pertaining to polydiacetylene-toluene-sulfonate are given as an illustration. The stability of the steady-state solution is examined, and the physical mechanism responsible for the bistability is discussed.

DOI
10.1103/physrevb.41.3280

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A new type of optical bistability mediated by phonon and virtual-exciton coupling is suggested for polymers. Numerical results with parameters pertaining to polydiacetylene-toluene-sulfonate are given as an illustration. The stability of the steady-state solution is examined, and the physical mechanism responsible for the bistability is discussed.
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An exciton-phonon mechanism for producing cavityless optical bistability is suggested. We consider the influence of the oscillating subsystem of a crystal on the absorption process of a laser wave in the region of exciton frequencies. It is shown that exciton-phonon interaction leads to nonlinear dependence of the absorption coefficient on the density of the exciton gas. The increase of absorption with increasing exciton density, however, is possible only in the frequency region on the long-wavelength tail of the exiton band. As a result, the exciton density of the crystal becomes a hysteresis function of external parameters (intensity of the incident wave, temperature, etc.). We calculate the absorption coefficient of excitons and define the frequency and temperature regions where optical bistability may exist. We analyze different relaxation mechanisms of excitons and explain the experimental results of observing optical bistability in different semiconductor crystals.