Nonlinear optics in gallium phosphide cavities: simultaneous second and third harmonic generation

TL;DR

This paper demonstrates simultaneous second and third harmonic generation in gallium phosphide microdisks, analyzing the nonlinear processes and mode interactions despite material absorption challenges.

Contribution

It provides new insights into the nonlinear optical processes in GaP cavities, highlighting the roles of direct and cascaded sum frequency generation at telecom wavelengths.

Findings

Both second and third harmonic signals are generated simultaneously.

The third harmonic generation is influenced by cavity mode detuning.

Nonlinear processes are significant despite material absorption.

Abstract

We demonstrate the simultaneous generation of second and third harmonic signals from a telecom wavelength pump in a gallium phosphide (GaP) microdisk. Using analysis of the power scaling of both the second and third harmonic outputs and calculations of nonlinear cavity mode coupling factors, we study contributions to the third harmonic signal from direct and cascaded sum frequency generation processes. We find that despite the relatively high material absorption in gallium phosphide at the third harmonic wavelength, both of these processes can be significant, with relative magnitudes that depend closely on the detuning between the second harmonic wavelength of the cavity modes.