Theoretical and Experimental Study of Optical Bistability in Four-Level Nonradiative Dyes
We consider bistability which occurs in materials which may be described by a multilevel energy spectrum for which bistability is caused by an intensity-dependent nonlinear refraction which is derived from the saturation of absorption. Such a model for a nonlinear refractive index was first introduced by Liao and Bloom to explain degenerate four-wave mixing in ruby.1 Since, in this system, optical bistability occurs at intensities near or higher than the saturation intensity, the typical power series expansion of the susceptibility is not valid. Correct analysis requires use of the functional form of the susceptibility. We provide here such an analysis for a four-level nonradiative dye with a relatively large unsaturable absorption loss. In this case optical bistability has been observed at intensities near or higher than the saturation intensity.
KeywordsSaturable Absorber Nonlinear Refractive Index Nonlinear Susceptibility Optical Bistability Saturation Intensity
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- 2.S.L. McCall and H.M. Gibbs, “Optical Bistability” Dissipative Systems in Quantum Optics, R. Bonifacio, ed., Springer Verlag, Berlin, 1982Google Scholar