非线性光学在科学技术的诸多领域发挥着重要作用。其发展得益于具有更高光学非线性的材料的发现与应用。本文展示了一种磷化铟镓（InGaP）集成光子学平台，可用于宽带、超高效的二阶非线性光学。InGaP 纳米光子波导在 1.55 $μ$m 泵浦波长下实现了二阶谐波生成，归一化效率达 $128,000\%$/W/cm$^2$，比电信 C 波段的最先进水平高出近两个数量级。此外，我们实现了一种超亮、宽带的时间-能量纠缠光子源，其光子对生成率为 97 GHz/mW，带宽为 115 nm，中心位于电信 C 波段。该 InGaP 纠缠光子源展现出高符合与偶然计数比（CAR）$>10^4$ 以及双光子干涉可见度 $>98\%$。该 InGaP 二阶非线性光子学平台将对非经典光生成、光信号处理和量子网络产生广泛影响。
英文摘要：
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 $μ$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.
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Kramers-Kronig causality in integrated photonics: The spectral tension between ultraviolet transition and mid-infrared absorption
Southern University of Science and Technology（南方科技大学）；International Quantum Academy（国际量子科学院）；Shenzhen Futian SUSTech Institute for Quantum Technology and Engineering（深圳福田南科大量子技术与工程研究院）；College of Physics and Optoelectronic Engineering, Shenzhen University（深圳大学物理与光电工程学院）；Institute of Advanced Photonics Technology, School of Information Engineering, Guangdong University of Technology（广东工业大学信息工程学院先进光子技术研究所）
