InGaP $\chi^{(2)}$ integrated photonics platform for broadband, ultra-efficient nonlinear conversion and entangled photon generation

TL;DR

This paper introduces an InGaP integrated photonics platform that achieves broadband, ultra-efficient second-order nonlinear optical processes and generates high-quality entangled photon pairs for quantum applications.

Contribution

It demonstrates a highly efficient InGaP nanophotonic waveguide for second-harmonic generation and a broadband entangled photon source with record performance metrics.

Findings

Normalized second-harmonic generation efficiency of 128,000%/W/cm²

Entangled photon source with 97 GHz/mW pair rate and 115 nm bandwidth

High two-photon interference visibility >98% and CAR >10^4

Abstract

Nonlinear optics plays an important role in many areas of science and technology. The advance of nonlinear optics is empowered by the discovery and utilization of materials with growing optical nonlinearity. Here we demonstrate an indium gallium phosphide (InGaP) integrated photonics platform for broadband, ultra-efficient second-order nonlinear optics. The InGaP nanophotonic waveguide enables second-harmonic generation with a normalized efficiency of $128,000\%$/W/cm$^2$ at 1.55 $\mu$m pump wavelength, nearly two orders of magnitude higher than the state of the art in the telecommunication C band. Further, we realize an ultra-bright, broadband time-energy entangled photon source with a pair generation rate of 97 GHz/mW and a bandwidth of 115 nm centered at the telecommunication C band. The InGaP entangled photon source shows high coincidence-to-accidental counts ratio CAR $>10^4$ and two-photon interference visibility $>98\%$. The InGaP second-order nonlinear photonics platform will have wide-ranging implications for non-classical light generation, optical signal processing, and quantum networking.