硅基光子集成芯片斯托克斯参数测量研究

It is of great significance to measure Stokes parameters of light in both fundamental and application research of light associated with polarization states. The rapid development of micro-nanophotonics offers new opportunities for measuring Stokes parameters of light in smaller sizes. This project focuses on the key scientific issue of miniaturizing and integrating measurement for light polarization state, and intends to study how to achieve the synchronous measurement of Stokes parameters of light with wide bandwidth and high precision on silicon-based photonic integrated devices. This research aims to solve the series problems of the conventional polarization detecting equipment composed of bulk optical components with complex structure, large volume and high cost, as well as the micro-nano polarimetry proposed in recent years with large insertion loss, low detection precision and complicated measurement. This research intends to create and integrate three kinds of polarization-dependent outputs on the silicon-based waveguide, i.e, x/y linear polarization output, diagonal polarization output and circular polarization output, which corresponds to the measurement of Stokes parameters S1, S2 and S3, respectively. The on-chip polarimetry in our research is based on the polarization-dependent excitation, conversion and coupled output on silicon-based waveguide, and thus the unit design of polarization measurement is fully controllable, thereby greatly improving the measurement performance of the device. The research that will be conducted in this project for the on-chip measurement of Stokes parameter of light can be used not only for polarization detecting, polarization-based multiplexing and signal processing in current integrated photonic currents, but also be hopefully applied to the future photonic polarization (spin)-based integrated quantum networks.

光的斯托克斯参数测量在偏振光学基础研究与应用研究中具有极为重要的意义。微纳光子学的迅速发展为在更小尺寸上实现光的斯托克斯参数测量提供了全新的机会。本项目围绕光偏振态测量的小型化与集成化关键科学问题，拟在硅基光子集成芯片上研究实现光斯托克斯参数的宽带宽高精度同步测量。研究旨在解决传统的偏振检测设备结构复杂、体积庞大、成本高，以及近几年提出的微纳偏振测量仪插损大、检测精度低、测量复杂等系列问题。研究拟在硅基波导上构建并集成三种偏振依赖输出单元，即：x/y线偏振、对角线偏振与圆偏振输出，分别对应斯托克斯参数S1、S2与S3的测量。研究是基于波导模式的偏振依赖性激发、转换与耦合输出，偏振测量单元设计完全可控，从而大幅提高器件的测量性能。本项目拟开展的片上斯托克斯参数测量研究，不仅能用于当前集成光子偏振态检测以及偏振光复用与信号处理，更有望应用于未来基于光子偏振（自旋）传输与控制的集成光量子网络中。

光的偏振态在光学基础研究与应用中具有重要的意义，微纳光子学的迅速发展为在更小尺度上测量光的斯托克斯参数以及研究与光偏振相关的物理现象提供了全新的机会。本项目围绕微纳波导传输媒介，研究了光的偏振态检测方案及其它相关物理规律。首先，项目针对片上硅基手性（自旋偏振态）耦合这一基本单元器件，提出了叉形倒拉锥纳米波导来提高耦合带宽，使手性耦合带宽大幅提升。数值结果显示，相比于原始倒拉锥波导，在保证手性耦合定向性大于0.9的情况下，手性耦合带宽能拓展到接近70纳米。其次，本项目设计并验证了一种基于偏振旋转/分束/相移器与定向耦合器结合的片上斯托克斯偏振检测方案。数值仿真结果显示，该方案能较好实现任意偏振态检测，且精度高，尺寸小，可调谐。再次，项目研究并发现对向传输的狭缝波导对电磁手性以及其梯度力有明显的增强效果。这种手性梯度力增强可用于手性纳米粒子的全光手性分离。与以往的全光手性分离比，其具有梯度力大、突破衍射极限、可大规模集成、开发成光流控技术等优点。项目研究对这一发现做了系统分析与验证。进一步，项目针对光纤圆柱形波导的模式、偏振、自旋以及轨道角动量等基本物理量进行系统研究，发现了一种基于TM01与TE01本征模退简并干涉的自旋-轨道相互作用，称之为自旋-轨道映射。该现象与传统的自旋轨道转换相比，不管在机理上，对传输介质的要求，还是基本光学现象方面，都有根本的不同之处。最后，针对光纤导波的本征模退简并现象，项目研究从另一角度解释了其原因，即利用射线光学，综合考虑传统的Goos–Hänchen与Imbert–Fedorov位移，结合涡旋模式扭转的坡印廷矢量来进行定性分析与定量证明。相比于传统的本征模解析分析，该方法更加直观形象，便于理解。本项目开展的片上偏振测量方案与相关研究，对当前集成光子偏振态检测技术以及偏振相关的光复用与信号处理技术有重要的推动作用，更有望开拓微纳光学与光纤光学的偏振相关新技术与新应用。