Modulational instability of optical beams in photorefractive media in the presence of two wave and four wave mixing effects

TL;DR

This paper investigates the modulational instability of optical beams in photorefractive media, focusing on two wave and four wave mixing effects, and derives models to analyze their impact on beam stability.

Contribution

It introduces a new model for forward four wave mixing in photorefractive media and analyzes the resulting modulational instability using linear stability analysis.

Findings

Instability gain is derived for both two wave and four wave mixing cases.

Self-phase-modulation effects are suppressed, highlighting holographic focusing nonlinearities.

The study provides insights into beam stability in photorefractive media with complex nonlinear interactions.

Abstract

Modulational instability in a photorefractive medium is studied in the presence of two wave mixing. We then propose and derive a model for forward four wave mixing in the photorefractive medium and investigate the modulational instability induced by four wave mixing effects. By using the standard linear stability analysis the instability gain is obtained. In both the cases, the geometry is such that the effect of self-phase-modulation self-focusing is suppressed and only the holographic focusing nonlinearity is acting.