Abstract

PAZ, José Luis; LASCANO, Luis  and  COSTA-VERA, Cesar. Nonlinear Optical Properties in Four-Wave Mixing Signals: Stochastic Considerations of Solvent and Spectral Diffusion. Rev Politéc. (Quito) [online]. 2019, vol.43, n.2, pp.7-20. ISSN 2477-8990.

Using the Optical Bloch equations, and considering a molecular system interacting with a thermal reservoir in Four-wave mixing spectroscopy, we derive analytical expressions for the nonlinear optical properties. In this work, we introduce different methodologies for the study of the macroscopic polarizations and nonlinear optical susceptibilities. In a two-level system, we have considered the collective effects of the thermal reservoir as a time dependent frequency, whose manifestation is the broadening of the upper level according to a prescribed random function. Here, the optical responses calculated through a methodology based on the averaging of the coherence obtained by the resolution of the optical stochastic Bloch equations. We were able to calculate the optical susceptibilities at different frequencies, depicted as numerical surfaces for the behavior of the optical responses, as function of the pump- and probe-frequency detuning factor and the strength of the noise source. Relaxation times using symmetry properties of the optical responses, effects of spectral diffusion on the third order nonlinear susceptibility for two- and three-level quantum systems, are studied. The results presented in this work show potential applications for the optical characterization of complex molecular systems.

Keywords : Optical susceptibility; absorptive and dispersive properties; four-wave mixing.

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