亚波长波导中偏振操控的理论和实验研究

Subwavelength polarization devices are of importance in highly integrated photonic circuit. Surface plasmon polaritons (SPP) are the transverse-magnetic (TM) waves propagating along the metal surface. The SPPs have subwavelength confinements, and they also exhibit inherent polarization dependence. Recently, the ultra-small polarization devices were numerically reported based on the hybrid plasmonic waveguides, which supported both of the SPP mode and the TE modes. Due to the presence of the dielectric waveguide in the hybrid plasmonic waveguide, the devices sizes were difficult to be downscaled to subwavelength scales. Moreover, the hybrid structures comprising of the dielectric and metal greatly increased the fabrication difficulty, and the experimental works were rare. To address the large structural size and fabrication difficulty, the pure metallic subwavelength waveguide structures are proposed to realize the polarization manipulation, including the polarization coupling, splitting, combining, and rotating. By this way, the polarization devices are considerably shrunk, which can greatly increase the integration density of the photonic circuits. The content of the project contains the design of the subwavelength plasmonic waveguides, the coupling between the light sources to the SPP modes, the realization of the polarization splitting, combining, and rotating in the subwavelength plasmonic waveguides, and the achievement of the subwavelength on-chip polarization devices.

亚波长偏振器件在高集成度光子回路中具有重要的应用。表面等离激元是金属表面的TM波，具有亚波长束缚，但同时又具有偏振依赖特性。目前超小的偏振器件基本都是基于既支持表面等离激元模式又支持介质TE模式的复合波导结构。由于金属介质复合结构加工困难，因此实验工作很少。另一方面，这种复合波导结构一方面由于介质波导的存在，尺寸很难达到亚波长以下。本项目针对复合波导偏振器件尺寸大、实验难以制备的难题，基于课题组前期研究基础提出在亚波长金属波导上研究光的偏振耦合、分束、合束、旋转等操控行为，从而实现突破衍射极限的偏振光子器件，极大地提高集成光子回路的集成密度。主要内容包括：设计出支持两个垂直偏振模式的亚波长表面等离激元波导；光场(尤其是纳米光源)不同偏振态到亚波长表面等离激元的定向耦合；在亚波长表面等离激元波导上设计微纳结构实现偏振分束、合束、旋转等，获得突破衍射极限的片上偏振器件。

亚波长片上偏振器件是高集成度光子回路和光子芯片中重要组成部分。针对复合波导偏振器件尺寸大、实验难以制备的难题，本项目提出在亚波长金属波导上研究光的偏振耦合、分束、合束、旋转等操控行为，从而实现突破衍射极限的偏振光子器件，极大地提高集成光子回路的集成密度。主要内容包括：设计出支持两个垂直偏振模式的亚波长表面等离激元波导；光场(尤其是纳米光源)不同偏振态到亚波长表面等离激元的定向耦合；在亚波长表面等离激元波导上设计微纳结构实现偏振分束、合束、旋转等，获得突破衍射极限的片上偏振器件。..在该项目的资助下，该项目严格按照任务书进行，在理论和实验方面取得了一定的成果，已发表SCI论文23篇，影响因子大于6的论文14篇，5篇被选为期刊的封面文章。包括一篇包括2篇Advanced Materials、1篇Laser & Photonics Reviews（封面）、3篇Advanced Optical Materials (2篇封面)、3篇ACS Photonics、3篇Nanoscale (1篇封面文章)、2篇Nanophotonics。这些工作获得了国内外同行的关注和认可，被Chemical Reviews, Advanced Optical Materials, Progress in Quantum Electronics等综述文章正面引用报道。因为申请者在表面等离激元器件方面的贡献，项目负责人受Advanced Optical Materials，Chinese Journal of Semiconductors，中国激光等期刊发表综述文章。其中Advanced Optical Materials期刊的Plasmonic devices综述文章(Plasmonic sensing and modulation based on Fano resonances)，被选为该期刊的封面文章，并在该期刊的名人堂(Hall of Fame)重点报道。在项目执行期间，项目负责人参加国内外学术会议13个，其中邀请报告11个。2019年获国家基金委优秀青年科学基金项目资助。2020年担任第九届中国光学学会基础光学专业委员会委员和《量子电子学报》第八届编委会委员。