集成光学微腔中的级联非线性效应及其在量子光源中的应用

Multi-photon quantum state is a key resource in quantum information processing. Traditionally, it is realized by paralleling multiple two-photon sources and performing linear optical operation and post-selection. Integrated optical microcavity can greatly enhance nonlinear interactions and enable the observation of multiple nonlinear processes that involves multiple resonant modes, generating the cascaded nonlinearity. The cascaded nonlinearity can generate multi-photon quantum states directly, which avoids probabilistic problems in paralleling and post-selection. It holds great potential to increase the brightness and scalability of quantum photon source. This project focuses on the cascaded nonlinear effect in optical microcavities and its applications in building quantum photon source. The following subjects will be included: (1) Investigation on the general approach to construct cascaded nonlinear effects in integrated microcavity and study the basic physical behavior; (2) Investigation on the multimode dispersion property of optical microcavity and physical realization of cascaded nonlinearity; (3) Investigation on bright telecom-visible entangled two-photon source and scalable multi-photon quantum photon sources in an integrated microcavity. The goal of this project is to find a general approach to construct cascaded nonlinearity in optical microcavity and increase the scalability of multi-photon quantum source. We expect to directly generate bright, telecom-visible entangled two-photon quantum state and scalable multi-photon quantum entangled state with brightness 1-2 orders of magnitude higher than traditional sources. Further, the project will explore the new physics in complex nonlinear optical systems and the applications of cascaded nonlinearity in both classical and quantum photonic devices.

多光子量子纠缠态是量子信息处理中的关键资源。传统方法利用并行的双光子源、线性光学操作和后选择概率性产生多光子量子态，其亮度和可扩展度受到限制。集成光学微腔的增强作用使多个谐振模式参与的多种非线性过程能够同时发生，形成级联非线性。这种多模参与的过程能够直接产生多光子量子态，避免传统方法的概率性问题，有望提升量子光源的亮度和光子数可扩展性。本项目围绕“集成光学微腔中的级联非线性效应及其在量子光源中的应用”的主题，具体研究：(1)集成光学微腔中级联非线性过程的人工构建与其基本物理行为效应、调控机制研究；(2)集成光学微腔的多模式色散调控与级联非线性的物理实现；(3) 级联非线性过程在量子光源中的应用。建立集成光学微腔中级联非线性过程构建的一般性方法，提高现有3、4光子量子光源的亮度1-2个数量级，提升光子数可扩展性。并进一步探索级联非线性中的新物理现象及其在集成经典与量子光子器件中的应用。

本项目依托于集成光子芯片上的波导、谐振腔等微纳光学结构，利用其增强光学非线性的能力和灵活色散调控的特点，从理论和实验上研究了多个模式同时参与、多种非线性效应同时发生这一复杂过程中的物理和应用。研究内容包含了对多模非线性过程的理论建模和数值计算、氮化铝集成光子芯片上级联非线性过程的实验实现以及该过程在量子纠缠光源中的应用。本项目的研究取得的重要结果包括：(1)建立了多模多非线性过程的统一理论框架并开发出了一套数值仿真程序，能够快速求解复杂非线性系统的动力学演化，并应用于光学频率梳的研究和单光子级非线性过程的研究；(2)在氮化铝集成光子芯片上，利用单个微环谐振腔同时实现了四波混频和光学和频，人工合成了有效的五波混频过程，其强度比材料本征响应高500倍以上；(3)利用级联非线性实现了可见-红外跨波段量子纠缠光源，并给出了可直接产生多光子量子纠缠态的方案，能够打破传统量子光源可扩展性受到的限制。本项目的研究拓展了集成非线性光子学新的应用方向，其研究成果在非线性频率转换、光频梳以及量子信息处理领域中具有重要应用潜力。