Zhang Qi, Qi Jiwei, Wu Qiang, Lu Yao, Zhao Wenjuan, Wang Ride, Pan Chongpei, Wang Shibiao, Xu Jingjun
Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, TEDA Institute of Applied Physics and School of physics, Nankai University, Tianjin, 300457, China.
Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, China.
Sci Rep. 2017 Dec 14;7(1):17602. doi: 10.1038/s41598-017-17712-4.
Highly intense terahertz electromagnetic field and efficiently surface localized terahertz field in subwavelength volumes are of vital importance for terahertz photonics integration, also will greatly accelerate the development for integrated applications in biochemical sensing, imaging, terahertz spectroscopy, enhancement of nonlinear effects and even quantum research. In this paper, we achieved large terahertz field enhancement and surface field localization through depositing a pair of Au composite antennas on a LiNbO subwavelength slab waveguide, which can serve as an excellent on-chip platform for terahertz research and application. The antennas consist of two opposing tip-to-tip triangles separated by a gap, and each triangle combines with a strip antenna. Time-resolved imaging and finite-difference time-domain method were used to resolve the characteristics of the designed antennas experimentally and simulatively. Through these methods, we demonstrated outstanding abilities of the platform: leading to a large electric field enhancement, concentrating almost full terahertz energy on the waveguide's surface when they are resonant with the terahertz waves and tunable resonant frequency. These abilities make the subwavelength waveguide coupling with the composite antennas be able to sever as a good integrated device to identify terahertz-sensitive small objects, or an excellent platform to terahertz spectroscopy and quantum research.
在亚波长体积中实现高强度太赫兹电磁场和高效的表面局域太赫兹场对于太赫兹光子学集成至关重要，这也将极大地加速其在生化传感、成像、太赫兹光谱学、非线性效应增强乃至量子研究等集成应用方面的发展。在本文中，我们通过在铌酸锂亚波长平板波导上沉积一对金复合天线，实现了太赫兹场的大幅增强和表面场局域化，该波导可作为太赫兹研究与应用的优良片上平台。天线由一对通过间隙隔开的对顶三角形组成，每个三角形与一个条形天线相结合。采用时间分辨成像和时域有限差分方法对所设计天线的特性进行了实验和模拟解析。通过这些方法，我们展示了该平台的卓越能力：实现了大幅电场增强，当与太赫兹波共振时，几乎将所有太赫兹能量集中在波导表面，且共振频率可调。这些能力使得亚波长波导与复合天线的耦合能够作为识别太赫兹敏感小物体的良好集成器件，或作为太赫兹光谱学和量子研究的优良平台。
