Second-harmonic generation in single-mode integrated waveguides through mode-shape modulation

TL;DR

This paper introduces a novel mode-shape-modulation technique for quasi-phase-matching in integrated waveguides, enabling efficient second-harmonic generation without periodic poling, demonstrated in lithium niobate ridge waveguides.

Contribution

It presents a simple, flexible method for quasi-phase-matching via waveguide width modulation, avoiding complex fabrication processes like periodic poling.

Findings

Demonstrated second-harmonic generation at 784 nm in lithium niobate waveguides.

Achieved quasi-phase-matching through mode-shape modulation without periodic poling.

Experimental validation confirms the effectiveness of the MSM technique.

Abstract

A simple and flexible technique for achieving quasi-phase-matching in integrated photonic waveguides without periodic poling is proposed and experimentally demonstrated, referred to as mode-shape-modulation (MSM). It employs a periodic variation of waveguide width to modulate the intensity of the pump wave, effectively suppressing out-of-phase light generation. This technique is applied to the case of second-harmonic generation in thin-film lithium niobate ridge waveguides. MSM waveguides are fabricated and characterized with pulsed-pumping in the near-infrared, showing harmonic generation at a signal wavelength of 784 nm.