Microwatts continuous-wave pumped second harmonic generation in few- and mono-layer GaSe

TL;DR

This paper reports the first demonstration of continuous-wave pumped second harmonic generation in few- and mono-layer GaSe flakes on silicon photonic crystal cavities, significantly reducing pump power and enhancing nonlinear optical processes.

Contribution

It introduces a novel CW pumped SHG in 2D GaSe on photonic cavities, leveraging high nonlinearity and resonance to enable low-power nonlinear optics.

Findings

SHG achieved with microwatt pump power

650 times stronger SHG than silicon third harmonic

Potential for integrated nonlinear optoelectronic devices

Abstract

We demonstrate the first achievement of continuous-wave (CW) pumped second harmonic generation (SHG) in few- and mono-layer gallium selenide (GaSe) flakes, which are coated on silicon photonic crystal (PC) cavities. Because of ultrahigh second order nonlinearity of the two-dimensional (2D) GaSe and localized resonant mode in the PC cavity, SHG's pump power is greatly reduced to microwatts. In a nine-layer GaSe coated PC cavity, while the optical power inside the GaSe flake is only 1.5 percent of that in the silicon PC slab, the SHG in GaSe is more than 650 times stronger than the third harmonic generation in silicon slab, indicating 2D GaSe's great potentials to strengthen nonlinear processes in silicon photonics. Our study opens up a new view to expand 2D materials' optoelectronic applications in nonlinear regime and chip-integrated active devices.