Quasi-phase-matching $\chi^{(3)}-$parametric interactions in sinusoidally-tapered waveguides

TL;DR

This paper demonstrates how sinusoidally-tapered waveguides can be used for efficient quasi-phase-matching in third-order nonlinear processes, significantly enhancing third-harmonic generation compared to uniform waveguides.

Contribution

It introduces a Fourier-series analysis method for designing quasi-phase-matching in sinusoidally-tapered waveguides, enabling orders-of-magnitude improvements in conversion efficiency.

Findings

Enhanced third-harmonic generation efficiency in tapered fibers

Conversion efficiency depends on modulation amplitude, period, and pump wavelength

Orders-of-magnitude increase in efficiency over uniform waveguides

Abstract

In this article, I show how periodically-tapered waveguides can be employed as efficient quasi-phase-matching schemes for four-wave mixing parametric processes in third-order nonlinear materials. As an example, a thorough study of enhancing third-harmonic generation in sinusoidally-tapered fibres has been conducted. The quasi-phase-matching condition has been obtained for nonlinear parametric interactions in these structures using Fourier-series analysis. The dependencies of the conversion efficiency of the third harmonic on the modulation amplitude, tapering period, longitudinal-propagation direction, and pump wavelength have been studied. In comparison to uniform waveguides, the conversion efficiency has been enhanced by orders of magnitudes. I envisage that this work can reshape the field of guided nonlinear optics using centrosymmetric materials.