Qingqing Cheng, Meilin Ma, Dong Yu, Zhixiong Shen, Jingya Xie, Juncheng Wang, Nianxi Xu, Hanming Guo, Wei Hu, Shuming Wang, Tao Li, Songlin Zhuang
https://www.sciencedirect.com/science/article/pii/S2095927319304621
Achromatic focusing is essential for broadband operation, which has recently been realized from visible to infrared wavelengths using a metasurface. Similarly, multi-terahertz functional devices can be encoded in a desired metasurface phase profile. However, metalenses suffer from larger chromatic aberrations because of the intrinsic dispersion of each unit element. Here, we propose an achromatic metalens with C-shaped unit elements working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the centre frequency. The designed metalens possesses a high working efficiency of more than 68% at the peak and a relatively high numerical aperture of 0.385. We further demonstrate the robustness of our C-shaped metalens, considering lateral shape deformations and deviations in the etching depth. Our metalens design opens an avenue for future applications of terahertz meta-devices in spectroscopy, time-of-flight tomography and hyperspectral imaging systems.
