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

ABSTRACT InGaP‐on‐insulator (InGaP‐OI), with its intrinsically high 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 mechanisms 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 quality factor enhancement at 780 nm, enabling a second‐harmonic generation efficiency of %/W and a degenerate photon‐pair generation rate of 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.