# Improved second harmonic performance in periodically poled LNOI waveguides through engineering of lateral leakage

## TL;DR

This paper explores how engineering waveguide structures in lithium niobate on insulator (LNOI) can mitigate lateral leakage, significantly enhancing second harmonic generation efficiency in nonlinear optical devices.

## Contribution

It provides design guidelines to prevent lateral leakage in LNOI waveguides, leading to improved second harmonic generation performance.

## Key findings

- Lateral leakage occurs for TE modes in LNOI ridge waveguides due to birefringence.
- Design considerations can effectively eliminate lateral leakage at the second harmonic wavelength.
- Achieved a peak second harmonic generation efficiency of approximately 1160% W-1cm-2.

## Abstract

In this contribution we investigate the impact of lateral leakage for linear and nonlinear optical waveguides in lithium niobate on insulator (LNOI). Silicon nitride (SiN) loaded and direct patterned lithium niobate cross-sections are investigated. We show that lateral leakage can take place for the TE mode in LNOI ridge waveguides (X-cut lithium niobate), due to the birefringence of the material. This work gives guidelines for designing waveguides in LNOI that do not suffer from the lateral leakage effect. By applying these design considerations, we avoided the lateral leakage effect at the second harmonic wavelength of a nonlinear optical waveguide in LNOI and demonstrate a peak second harmonic generation conversion efficiency of ~1160% W-1cm-2.

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Source: https://tomesphere.com/paper/1906.02383