Observation of second-harmonic generation in silicon nitride waveguides through bulk nonlinearities

TL;DR

This paper reports the experimental observation of second-harmonic generation in silicon nitride waveguides, revealing bulk nonlinearities and demonstrating active tuning capabilities, which could enable advanced nanophotonic devices in integrated photonics.

Contribution

First experimental demonstration of bulk second-order nonlinearities in silicon nitride waveguides with dispersion engineering and active tuning, expanding their application potential.

Findings

Observation of second-harmonic generation in silicon nitride.

Identification of multiple nonlinear susceptibility components.

Active tuning of the second-harmonic signal with bias voltages.

Abstract

We present experimental results on the observation of a bulk second-order nonlinear susceptibility derived from both free-space and integrated measurements in silicon nitride. Phase-matching is achieved through dispersion engineering of the waveguide cross-section, independently revealing multiple components of the nonlinear susceptibility, namely X(2)yyy and X(2)xxy. Additionally, we show how the generated second-harmonic signal may be actively tuned through the application of bias voltages across silicon nitride. The nonlinear material properties measured here are anticipated to allow for the practical realization of new nanophotonic devices in CMOS-compatible silicon nitride waveguides, adding to their viability for telecommunication, data communication, and optical signal processing applications.