Efficient and robust second-harmonic generation in thin-film lithium niobate using modal phase matching

TL;DR

This paper presents a design for a thin-film lithium niobate waveguide that achieves efficient, robust second-harmonic generation through modal phase matching, offering a scalable alternative to PPLN with high conversion efficiency.

Contribution

The authors introduce a double-ridge waveguide design on LNOI that enables perfect phase matching and high efficiency SHG, advancing scalable integrated nonlinear photonics.

Findings

Achieved conversion efficiency of 3.92/W in a 1-cm waveguide.

Designed a waveguide with perfect phase matching between fundamental and higher-order modes.

Demonstrated potential for entangled photon pair generation in the infrared C-band.

Abstract

A double-ridge waveguide is designed for efficient and robust second-harmonic generation (SHG) using the thin-film lithium-niobate-on-insulator (LNOI) platform. Perfect phase matching (PhM) is achieved between the fundamental waveguide mode at 1550 nm and a higher-order mode at the second harmonic. The fabrication tolerances of the PhM condition are simulated using a finite-difference method mode solver, and conversion efficiencies as high as 3.92/W are obtained for a 1-cm long waveguide. This design allows access to the largest element of the second-order nonlinear susceptibility tensor, and represents a scalable alternative to waveguides based on periodically-poled lithium niobate (PPLN). The design has the potential for generating pairs of entangled photons in the infrared C-band by spontaneous parametric down-conversion (SPDC).