High-Efficiency InGaP-on-Insulator Microresonator Nonlinear Conversion and Entanglement Generation

TL;DR

This paper demonstrates a low-loss, high-efficiency InGaP-on-insulator microresonator platform for nonlinear optical conversion and entanglement generation, with significant performance improvements.

Contribution

It identifies and mitigates propagation loss mechanisms, enabling high nonlinear conversion efficiency and photon-pair generation in integrated photonics.

Findings

Achieved propagation loss as low as 0.49 dB/cm at 1560 nm

Demonstrated second-harmonic generation efficiency of 3.01×10^5 %/W

Photon-pair generation rate of 11.7 MHz/μW with high coincidence-to-accidental ratio

Abstract

InGaP-on-insulator, with its intrinsically high $\chi^{(2)}$ optical nonlinearity, has emerged as an efficient and bright integrated photonic platform for frequency conversion and on-chip entanglement generation, but high waveguide propagation loss in the visible wavelength range has limited its overall performance. Here, we identify the dominant loss mechanism through mode-profile analysis and effectively mitigate the loss using a surface treatment method. Statistical analysis of the resonator quality factor and propagation loss reveals the optimal ring radius that maintains a strong nonlinear interaction while suppressing significant bending related loss, resulting in loss as low as 0.49 dB/cm (4.31 dB/cm) at 1560 nm (780 nm). The method provides a 3.5--4$\times$ linear performance enhancement, enabling a second-harmonic generation efficiency of $3.01\times10^{5}$ %/W and a photon-pair generation rate of $11.7,\mathrm{MHz}/\mu\mathrm{W}$ and coincidence-to-accidental ratio as high as 10,000. The quasi-phase matching condition is experimentally verified, and nonlinear conversion is systematically characterized across the entire parameter space. This work establishes a scalable pathway for classical and quantum photonics in a low-loss, highly nonlinear, and wafer-scale integration platform.