Efficient continuous-wave nonlinear frequency conversion in high-Q Gallium Nitride photonic crystal cavities on Silicon

TL;DR

This paper demonstrates efficient continuous-wave nonlinear frequency conversion, including second and third harmonic generation, in high-Q gallium nitride photonic crystal cavities on silicon, highlighting their potential for integrated nonlinear optics.

Contribution

It reports the first high-Q gallium nitride photonic crystal cavities with near-theoretical quality factors enabling efficient nonlinear frequency conversion under continuous-wave excitation.

Findings

Achieved normalized SHG conversion efficiency of 2.4×10^{-3} W^{-1}

Detected SHG emission power up to 0.74 nW without saturation

Validated gallium nitride's suitability for integrated nonlinear optical processing

Abstract

We report on nonlinear frequency conversion from the telecom range via second harmonic generation (SHG) and third harmonic generation (THG) in suspended gallium nitride slab photonic crystal (PhC) cavities on silicon, under continuous-wave resonant excitation. Optimized two-dimensional PhC cavities with augmented far-field coupling have been characterized with quality factors as high as 4.4$\times10^{4}$, approaching the computed theoretical values. The strong enhancement in light confinement has enabled efficient SHG, achieving normalized conversion efficiency of 2.4$\times10^{-3}$ $W^{-1}$, as well as simultaneous THG. SHG emission power of up to 0.74 nW has been detected without saturation. The results herein validate the suitability of gallium nitride for integrated nonlinear optical processing.