Demonstration of the spectral and the geometrical criteria that control high-reflectivity Brillouin-enhanced four-wave mixing

Abstract

The interplay between frequency and geometry in high-reflectivity Brillouin-enhanced four-wave mixing (BEFWM) is examined. We obtain detailed knowledge of the frequency relationship among all four interacting beams by using a unique laser system that directly supplies all three BEFWM input beams with independent and precise relative frequency control and by analyzing the phase-conjugate output spectrum. In accordance with an existing model, geometry measurements clearly confirm an inverse relationship between pump–pump and pump–signal angles when the input frequencies are fixed, and the total phase mismatch is found to be constant over a broad range of spectrally and spatially diverse BEFWM conformations. Output detunings similar to previously reported input detunings are observed. Line-shape analysis of the various resonances supports the concept that high-reflectivity BEFWM arises from the formation of distinct read and write gratings and that the energy transfer between them is controlled by a relatively broad phase-mismatch range.