Efficient Terahertz Generation in Triply Resonant Nonlinear Photonic Crystal Microcavities

TL;DR

This paper introduces a novel triply resonant photonic crystal cavity system that significantly enhances terahertz generation via difference-frequency generation, achieving near-complete pump depletion and high conversion efficiency.

Contribution

It presents a new design for triply resonant photonic crystal cavities enabling efficient THz generation with quantum-limited conversion, using coupled-mode theory for analysis.

Findings

High nonlinear overlap achieved through coupling THz and near-infrared cavities.

Complete depletion of pump frequency possible in feasible geometries.

Conversion efficiency can be optimized by adjusting mode Q-factors.

Abstract

We propose a scheme for efficient cavity-enhanced nonlinear THz generation via difference-frequency generation (DFG) processes using a triply resonant system based on photonic crystal cavities. We show that high nonlinear overlap can be achieved by coupling a THz cavity to a doubly-resonant, dual-polarization near-infrared (e.g. telecom band) photonic-crystal nanobeam cavity, allowing the mixing of three mutually orthogonal fundamental cavity modes through a chi(2) nonlinearity. We demonstrate through coupled-mode theory that complete depletion of the pump frequency - i.e., quantum-limited conversion - is possible in an experimentally feasible geometry, with the operating output power at the point of optimal total conversion efficiency adjustable by varying the mode quality (Q) factors.