High-efficiency second-harmonic and sum-frequency generation in a silicon nitride microring integrated with few-layer GaSe

TL;DR

This paper demonstrates high-efficiency second-harmonic and sum-frequency generation in silicon nitride microring resonators integrated with few-layer GaSe, leveraging the material's high second-order nonlinear susceptibility for advanced nonlinear photonic applications.

Contribution

The study introduces a novel integration of GaSe with SiN microrings to enable efficient second-order nonlinear processes, overcoming SiN's centrosymmetry limitations.

Findings

Achieved 849%/W second-harmonic generation efficiency.

Achieved 123%/W sum-frequency generation efficiency.

Demonstrated effective phase-matching and resonance enhancement.

Abstract

Silicon nitride (SiN) photonics platform has attributes of ultra-low linear and nonlinear propagation losses and CMOS-compatible fabrication process, promising large-scale multifunctional photonic circuits. However, the centrosymmetric nature of SiN inhibits second-order nonlinear optical responses in its photonics platform, which is desirable for developing efficient nonlinear active devices. Here, we demonstrate high-efficiency second-order nonlinear processes in SiN photonics platform by integrating a few-layer GaSe flake on a SiN microring resonator. With the pump of microwatts continuous-wave lasers, second-harmonic generation and sum-frequency generation with the conversion efficiencies of 849%/W and 123%/W, respectively, are achieved, which benefit from the ultrahigh second-order nonlinear susceptibility of GaSe, resonance enhanced GaSe-light interaction, and phase-matching condition satisfied by the mode engineering. Combining with the easy integration, the GaSe-assisted high-efficiency second-order nonlinear processes offer a new route to enriching already strong functionality of SiN photonics platform in nonlinear optics.