Broadband achromatic metalens in terahertz regime

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2019,（20）
• 页码范围: 1525-1531
• 页数: 7页
• 语种: 英文

摘要

Achromatic focusing is essential for broadband operation,which has recently been realised 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.