中国激光, 2019, 46 (6): 0614006, 网络出版: 2019-06-14
太赫兹液晶可调谐功能器件 
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Terahertz Tunable Devices Based on Liquid Crystal
图 & 表
图 1. 三种向列相液晶在THz波段的折射率。(a)实验原理示意图;(b) 5CB液晶折射率谱线;(c) E7液晶折射率谱线;(d) BNHR液晶折射率谱线[62]
Fig. 1. Refractive indexes of three nematic liquid crystals in THz regime. (a) Principle diagram of experiment; (b) refractive index spectra of 5CB liquid crystal; (c) refractive index spectra of E7 liquid crystal; (d) refractive index spectra of BNHR liquid crystal[62]
图 2. 实验测得双频液晶(DP002-016)的THz双折射特性。(a)入射光的偏振态沿着x轴的时域信号;(b)沿着y轴的时域信号;(c) x轴方向的折射率谱;(d) y轴方向的折射率谱;(e) x轴方向的消光系数;(f) y轴方向的消光系数[63]
Fig. 2. Experimentally measured THz birefringent performance of dual-frequency liquid crystal (DP002-016). (a) Time-domain signal of incident light polarization along x-axis; (b) time-domain signal along y-axis; (c) refractive index spectra along x-axis; (d) refractive index spectra along y-axis; (e) extinction coefficient along x-axis; (f) extinction coefficient along y-axis[63]
图 3. 双频液晶(DP002-016)随交变电场频率变化的THz双折射和相移特性。(a)双频液晶在1 kHz和100 kHz 交变电场下的液晶分子排布示意图;(b)群折射率随交变频率变化的曲线;(c)双折射相移谱线[63]
Fig. 3. THz birefringent and phase shift performances of dual-frequency liquid crystal (DP002-016) versus frequency of alternating electric field. (a) Schematic of liquid crystal molecular arrangement under alternating electric fields of 1 kHz and 100 kHz; (b) group refractive index versus alternating frequency; (c) phase shift spectra of birefringence[63]
图 4. 太赫兹金属光子晶体可调谐滤波器的传输特性。(a)在不同液晶有效折射率nLC下液晶填充PC器件的透射率谱;(b) PC器件结构示意图;(c) PC器件开、关频率下的稳态场分布;(d)在不同液晶有效折射率nLC下液晶填充PCW器件的透过率谱;(e) PCW器件结构示意图;(f) PCW器件开、关频率下的稳态场分布[86]
Fig. 4. Transmission characteristics of THz metal photonic crystal tunable filters. (a) Transmission spectra of liquid crystal-filled PC device under different effective refractive indexes nLC of liquid crystal; (b) structural diagram of PC device; (c) steady-state field distributions at ON and OFF frequencies of PC device; (d) transmission spectra of liquid crystal-filled PCW device under different effective refractive indexes nLC of liquid crystal; (e) structural diagram of PCW device; (f) steady-stat
图 5. 可调控太赫兹EIT与EIA超材料器件的传输特性实验结果。θ=0°时外电场沿着y方向时液晶超材料(a)示意图及(b)传输谱线;θ=0°时外电场沿着x方向时液晶超材料(c)示意图及(d)传输谱线;θ=90°时外电场沿着y方向时液晶超材料(e)示意图及(f)传输谱线[87]
Fig. 5. Experimental results of transmission characteristics of tunable THz EIT and EIA metamaterial devices. (a) Schematic and (b) transmission spectra of liquid crystal metamaterial when external electric field is along y direction at θ=0°; (c) schematic and (d) transmission spectra of liquid crystal metamaterial when external electric field is along x direction at θ=0°; (e) schematic and (f) transmission spectra when external electric field is along y direction at θ=90°[87]
图 6. 基于栅-格复合介质超表面结构的太赫兹液晶相移器的实验结果。(a)液晶填充介质超表面的3D结构示意图;(b)随外电场变化的有效折射率谱;(c)在0.7 THz频率处三种基于不同介质基板的电控液晶相移器随偏置电场变化的相移曲线[97]
Fig. 6. Experimental results of THz liquid crystal phase shifter based on grid-lattice composite dielectric metasurface structure. (a) 3D structural diagram of liquid crystal filled dielectric metasurface; (b) effective refractive index spectra for different external electric fields; (c) phase shift of three electronically controlled liquid crystal phase shifters based on different dielectric substrates versus bias electric field at 0.7 THz [97]
图 7. 基于电控液晶-石墨烯光栅的宽带可调QWP的仿真结果。(a)基于PGGLC的宽带可调谐液晶相移器的示意图;(b)偏振转换示意图以及两种QWP的工作曲线对比图[98]
Fig. 7. Simulation results of broadband tunable QWP based on electronically controlled liquid crystal-graphene grating. (a) Schematic of broadband tunable QWP based on PGGLC; (b) schematic of polarization conversion and comparison of operating curves of two QWPs[98]
表 1几种常见液晶材料在THz波段的光学各向异性参数
Table1. Optical anisotropy parameters of several common liquid crystals in THz regime
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表 2三种液晶在0.2~1 THz频率波段的光学各向异性参数
Table2. Optical anisotropy parameters of liquid crystal in THz regime
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冀允允, 范飞, 于建平, 许士通, 程洁嵘, 王湘晖, 常胜江. 太赫兹液晶可调谐功能器件[J]. 中国激光, 2019, 46(6): 0614006. Yunyun Ji, Fei Fan, Jianping Yu, Shitong Xu, Jierong Cheng, Xianghui Wang, Shengjiang Chang. Terahertz Tunable Devices Based on Liquid Crystal[J]. Chinese Journal of Lasers, 2019, 46(6): 0614006.
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