InGaP quantum nanophotonic integrated circuits with 1.5% nonlinearity-to-loss ratio

Optical nonlinearity plays a pivotal role in quantum information processing using photons, from heralded single-photon sources and coherent wavelength conversion to long-sought quantum repeaters. Despite the availability of strong dipole coupling to quantum emitters, achieving strong bulk optical nonlinearity is highly desirable. Here, we realize quantum nanophotonic integrated circuits in thin-film InGaP with, to our knowledge, a record-high ratio of 1.5% between the single-photon nonlinear coupling rate (g/2 pi = 11.2 MHz) and cavity-photon loss rate. We demonstrate second-harmonic generation with an efficiency of 71200 +/- 10300%/W in the InGaP photonic circuit and photon-pair generation via degenerate spontaneous parametric downconversion with an ultrahigh rate exceeding 27.5 MHz/mu W-an order of magnitude improvement of the state of the art-and a large coincidence-to-accidental ratio up to 1.4 x 10(4). Our work shows InGaP as a potentially transcending platform for quantum nonlinear optics and quantum information applications. (C) 2022 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This study realizes quantum nanophotonic integrated circuits in thin-film InGaP with strong optical nonlinearity, including efficient second-harmonic generation and generation of a large number of photon pairs.