Birefringence phase-matched direct third-harmonic generation in a ridge optical waveguide based on a KTiOPO4 single crystal

Augustin Vernay,Florent Bassignot,Corinne Félix,Mathieu Chauvet,Véronique Boutou,Benoit Boulanger,David Jegouso

doi:10.1364/oe.432636

Abstract

Birefringence phase-matched third-harmonic generation at 1594 nm is performed for the first time in a KTiOPO4 single crystal micrometric ridge waveguide. The energy conversion efficiency reaches 3.4% for a pump energy as low as 2 µJ over a pulse duration of 15 ps at a repetition rate of 10 Hz. Strong agreements between theory and experiments for both phase-matching and conversion efficiency is obtained, which let us envision future triple photon generation quantum experiments.

Highlights

Beside efficient generation of short wavelengths, nonlinear Third-Harmonic Generation (THG) components have the thrilling potential for novel quantum optical experiments based on direct Triple Photons Generation (TPG) [1,2]
We report on the first experimental demonstration of direct THG in micrometric KTP ridge waveguides
We have shown that KTP ridge waveguides are good candidates for efficient phasematched THG of which we made the first experimental demonstration

Summary

Introduction

Beside efficient generation of short wavelengths, nonlinear Third-Harmonic Generation (THG) components have the thrilling potential for novel quantum optical experiments based on direct Triple Photons Generation (TPG) [1,2]. Promising results have been obtained in planar periodically-poled LiNbO3 (PPLN) waveguides [7] and in ridge waveguides using two PPLN crystals [7,8] The latter nonlinear micrometric ridge waveguides are emerging due to their high frequency conversion efficiency and good matching with optical fibers [8,9]. Demonstrations have been realized in ridge waveguides carved in KTP bulk single crystals exploiting birefringence phase-matching (BPM) [10,11] or in QPM periodically-poled KTP [12,13] showing strong performances for second-harmonic generation. This study is a preliminary step for designing further quantum optical experiments based on direct Triple Photons Generation (TPG), i.e. 3ω → ω + ω + ω, that is the exact reverse process of THG, exhibiting the same BPM conditions [2].

Design of a Y-cut ridge waveguide

Fabrication and geometrical characterization of the waveguide

BPM wavelengths and spectral acceptance

Conversion efficiency

Findings

Conclusions