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TE0导模干涉刻写周期可调亚波长光栅理论研究
引用本文:王茹,王向贤,杨华,叶松.TE0导模干涉刻写周期可调亚波长光栅理论研究[J].物理学报,2016,65(9):94206-094206.
作者姓名:王茹  王向贤  杨华  叶松
作者单位:1. 兰州理工大学理学院, 兰州 730050; 2. 巢湖学院机械与电子工程学院, 合肥 238000
基金项目:国家重点基础研究发展计划(批准号: 2013CBA01703)、 国家自然科学基金(批准号: 61505074)、兰州理工大学红柳青年教师培养计划(批准号: Q201509)和巢湖学院自然科学基金(批准号: XLZ201201)资助的课题.
摘    要:通过棱镜耦合激发非对称金属包覆介质波导结构中的TE0导波模式, 利用两束TE0模的干涉从理论上实现了周期可调的亚波长光栅刻写. 分析了TE0模式的色散关系, 刻写亚波长光栅的周期与激发光源、棱镜折射率、光刻胶薄膜厚度及折射率之间的关系. 用有限元方法数值模拟了金属薄膜、光刻胶薄膜和空气多层结构中TE0导模的干涉场分布. 研究发现, 激发光源波长越短, TE0 模干涉刻写的亚波长光栅周期越小; 光刻胶越厚, 刻写的亚波长光栅周期越小; 高折射率光刻胶有利于更小周期亚波长光栅的刻写. 相较于表面等离子体干涉光刻, 基于TE0 模的干涉可在厚光刻胶条件下通过改变激发光源、棱镜折射率、光刻胶材料折射率、特别是光刻胶薄膜的厚度等多种方式实现对亚波长光栅周期的有效调控.

关 键 词:亚波长光栅  导模  色散曲线  有限元方法
收稿时间:2015-12-03

Theoretical investigation of adjustable period sub-wavelength grating inscribed by TE0 waveguide modes interference lithography
Wang Ru,Wang Xiang-Xian,Yang Hua,Ye Song.Theoretical investigation of adjustable period sub-wavelength grating inscribed by TE0 waveguide modes interference lithography[J].Acta Physica Sinica,2016,65(9):94206-094206.
Authors:Wang Ru  Wang Xiang-Xian  Yang Hua  Ye Song
Institution:1. School of Science, Lanzhou University of Technology, Lanzhou 730050, China; 2. College of Mechanical and Electrical Engineering, Chaohu University, Hefei 238000, China
Abstract:Sub-wavelength grating is a critical element in micro and nano-photonics. So its fabrication and application have attracted a great deal of research attention. While the existing lithography technologies of sub-wavelength grating fabrication have some insufficient points, such as high cost, low output, technical complexity, or difficult to change the period of the sub-wavelength grating. In this paper, an adjustable period and large area sub-wavelength grating with low cost and maskless is proposed and theoretically realized. The sub-wavelength grating is inscribed by the interference between two TE0 waveguide modes, where the TE0 waveguide mode is existent in an asymmetric metal-cladding dielectric waveguide structure excited by the prism coupling method. The dispersion curve of TE0 waveguide mode, the relationship between the period of the sub-wavelength grating and the exciting light source, the refractive index of the prism and the photoresist, especially the thickness of the photoresist are theoretically analyzed in detail. The distribution of the interference optical field of TE0 waveguide mode in the multilayer structure including metal film, photoresist and air layer is numerically simulated using the finite element method. The shorter the exciting light wavelength with the identical photoresist condition, the smaller the period of sub-wavelength grating inscribed by TE0 waveguide modes interference lithography is. For further studying the influences of refractive index and thickness of photoresist and the refractive index of the prism on the period of sub-wavelength grating, the exciting light with 442 nm wavelength and the Ag matel film are used. The period of sub-wavelength grating is smaller with thicker photoresist film, when the refractive indexes of photoresist and prism are the same. The larger refractive index of photoresist is beneficial to inscribing the sub-wavelength grating with smaller period when the refractive index of prism and the thickness of photoresist are identical. The prism with higher refractive index can provide wave vector-matching condition with lager propagation constant, and can inscribe sub-wavelength grating with smaller period. Compared with surface plasmons interference lithography which needs the thicker photoresist film due to the finite penetration depth of SPs, TE0 waveguide modes interference can realize adjustableperiod sub-wavelength grating writing for thicker photoresist condition by changing exciting light source, the refractive index of prism, the refractive index of photoresist and especially the thickness of photoresist. The realization of adjustable period sub-wavelength grating inscribed by TE0 waveguide modes interference lithography will provide important theoretical support for reducing the fabrication cost of sub-wavelength gratings and broadening the application scope of sub-wavelength grating.
Keywords:sub-wavelength grating  waveguide mode  dispersion curve  the finite element method
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