Dramatic Raman Gain Suppression in the Vicinity of the Zero Dispersion Point in Gas-Filled Hollow-Core Photonic Crystal Fiber

TL;DR

This paper demonstrates a significant suppression of Raman gain in hydrogen-filled hollow-core photonic crystal fibers by tuning the zero dispersion point near the pump wavelength, enabling new nonlinear optical explorations.

Contribution

It introduces a novel method to achieve dramatic Raman gain suppression in gas-filled fibers by pressure tuning the zero dispersion point close to the pump wavelength.

Findings

Complete suppression of Stokes light at specific pressures.

Enabling exploration of weaker nonlinear processes.

Long collinear interaction lengths achieved.

Abstract

In 1964 Bloembergen and Shen predicted that Raman gain could be suppressed if the rates of phonon creation and annihilation (by inelastic scattering) exactly balance. This is only possible if the momentum required for each process is identical, i.e., phonon coherence waves created by pump-to-Stokes scattering are identical to those annihilated in pump-to-anti-Stokes scattering. In bulk gas cells, this can only be achieved over limited interaction lengths at an oblique angle to the pump axis. Here we report a simple system that provides dramatic Raman gain suppression over long collinear path-lengths in hydrogen. It consists of a gas-filled hollow-core photonic crystal fiber whose zero dispersion point is pressure-adjusted to lie close to the pump laser wavelength. At a certain precise pressure, generation of Stokes light in the fundamental mode is completely suppressed, allowing other much weaker nonlinear processes to be explored.