基于光热折变玻璃设计的太赫兹超透镜  

Designed Terahertz Metalenses Based on Photo-Thermo-Refractive Glass

作　　者：咸寅龙 朱治昱 何冬兵[1] Xian Yinlong;Zhu Zhiyu;He Dongbing(Key Laboratory of Materials for High Power Laser,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院上海光学精密机械研究所高功率激光单元技术实验室,上海201800 [2]中国科学院大学材料与光电研究中心,北京100049

出　　处：《中国激光》2024年第22期243-249,共7页Chinese Journal of Lasers

摘　　要：为探索光热折变(PTR)玻璃在太赫兹领域中的应用,对PTR玻璃进行了太赫兹时域透过光谱扫描,获得了PTR玻璃样品的吸收系数和折射率。使用PTR玻璃作为超透镜基底,设计出环形开口谐振环太赫兹超透镜单元。使用电磁仿真软件,通过对设计单元的环宽、开口大小和旋转角度进行仿真,获得了具有较高光学透过率且能同时实现2π相位覆盖的超透镜单元结构。通过对超透镜单元进行排布,设计出焦距分别为3000、5000、8000和10000μm的聚焦超透镜,并对其聚焦效果进行了仿真验证。仿真结果表明,PTR玻璃可以作为太赫兹超透镜的基底,拓展了PTR玻璃的应用范围。Objective Terahertz metalenses have broad prospects in the future;however, currently, common metalens preparation methods such as lithography, electron beam lithography(EBL), and focused ion beam(FIB) usually require the use of a photoresist, which is cumbersome. Using photothermo-refractive(PTR) glass as a substrate eliminates the need for a photoresist during the preparation process. PTR glass is a UV-sensitive silicate glass material doped with photosensitive elements, such as Ce, Ag, and Sn. After UV exposure and thermal treatment, small NaF microcrystals precipitate. Owing to the different etching rates of hydrofluoric acid on the PTR glass substrate and NaF microcrystals, selective exposure of the area to be etched can be achieved, resulting in the desired groove structure. To obtain a complete metalens unit structure, metal thin films can be prepared in the grooves using methods such as evaporation, magnetron sputtering, atomic layer deposition, and chemical vapor deposition. To verify whether PTR glass can be applied to metalenses, THz metalenses are designed using PTR glass as a substrate.Methods We measure and analyze the absorption coefficient and refractive index of PTR glass in the terahertz band by scanning its terahertz transmission spectrum(Fig. 2) and obtain the relative dielectric constant of the material. A cell simulation model is constructed in COMSOL at a working frequency of 0.4 THz [Fig. 3(a)], and the cell structure is simulated to obtain the cell transmittance and phase.Results and Discussions Using the control-variable method, we simulate the ring width, opening angle, and rotation angle of the resonant ring, obtaining nine structures(Table 1). According to Formula(5), we arrange the units to obtain metalenses with focal lengths of 3000, 5000, 8000, and 10000 μm with numerical apertures of 0.6042, 0.4819, 0.3960, and 0.3593, respectively. After analyzing the electric-field intensity of the metalens(Fig. 5), we obtain the normalized electric-field intensity along the x-direction at the

关 键 词：PTR玻璃 太赫兹波 超透镜 

分 类 号：O434.3[机械工程—光学工程]