Low-power continuous-wave second harmonic generation in semiconductor nanowires

TL;DR

This paper demonstrates low-power continuous-wave second harmonic generation in semiconductor nanowires integrated with photonic crystal cavities, significantly reducing power requirements for nonlinear optical applications on-chip.

Contribution

It introduces a novel integration of nanowires with photonic crystal cavities enabling efficient SHG at microwatt power levels, a substantial improvement over previous high-power pulsed methods.

Findings

Achieved SHG with ~3 μW CW laser power

Cavity-enhancement factor estimated around 150

SHG in nanowires exceeds silicon third harmonic generation by over two orders of magnitude

Abstract

Semiconductor nanowires (NWs) are promising for realizing various on-chip nonlinear optical devices, due to their nanoscale lateral confinement and strong light-matter interaction. However, high-intensity pulsed pump lasers are typically needed to exploit their optical nonlinearity because light couples poorly with nanometric-size wires. Here, we demonstrate microwatts continuous-wave light pumped second harmonic generation (SHG) in AlGaAs NWs by integrating them with silicon planar photonic crystal cavities. Light-NW coupling is enhanced effectively by the extremely localized cavity mode at the subwavelength scale. Strong SHG is obtained even with a continuous-wave laser excitation with a pump power down to ~3 uW, and the cavity-enhancement factor is estimated around 150. Additionally, in the integrated device, the NW's SHG is more than two-order of magnitude stronger than third harmonic generations in the silicon slab, though the NW only couple s with less than 1% of the cavity mode. This significantly reduced power-requirement of NW's nonlinear frequency conversion would promote NW-based building blocks for nonlinear optics, specially in chip-integrated coherent light sources, entangled photon-pairs and signal processing devices.