Nonlinear stimulated Brillouin scattering in a single-mode optical fiber

TL;DR

This paper predicts and demonstrates a novel nonlinear stimulated Brillouin scattering effect in single-mode fibers, involving higher-order phonon processes and unique gain features at specific detunings, requiring counter-propagating pumps.

Contribution

It introduces a new nonlinear optical phenomenon in fibers, expanding understanding of phonon interactions beyond conventional stimulated Brillouin scattering.

Findings

Observation of Stokes gain at half the conventional Brillouin frequency

Absence of anti-Stokes absorption at the opposite detuning

Requirement of counter-propagating pump beams for phase-matching

Abstract

We predict and experimentally observe a nonlinear variant of stimulated Brillouin scattering in a single-mode fiber that arises from consideration of higher-order processes for phonon generation. The effect manifests itself at high laser excitation as the appearance of Stokes gain for a detuning equal to half of the conventional Brillouin frequency in the fiber, with no accompanying anti-Stokes absorption at the opposite detuning, and requires counter-propagating pump beams for phase-matching. We believe that this could be a new nonlinear optical effect that has not been observed before.