Abstract-Achromatic terahertz Airy beam generation with dielectric metasurfaces

 

Qingqing Cheng , Juncheng Wang, Ling Ma, Zhixiong Shen, Jing Zhang, Xiaoying Zheng ,Tao Chen, Ye Yu, Dong Yu, Qiong He, Wei Hu, Tao Li, Songlin Zhuang,  Lei Zhou

https://www.degruyter.com/view/journals/nanoph/ahead-of-print/article-10.1515-nanoph-2020-0536/article-10.1515-nanoph-2020-0536.xml?rskey=WV2s5h&result=7&tab_body=abstract

Airy beams exhibit intriguing properties such as nonspreading, self-bending, and self-healing and have attracted considerable recent interest because of their many potential applications in photonics, such as to beam focusing, light-sheet microscopy, and biomedical imaging. However, previous approaches to generate Airy beams using photonic structures have suffered from severe chromatic problems arising from strong frequency dispersion of the scatterers. Here, we design and fabricate a metasurface composed of silicon posts for the frequency range 0.4–0.8 THz in transmission mode, and we experimentally demonstrate achromatic Airy beams exhibiting autofocusing properties. We further show numerically that a generated achromatic Airy-beam-based metalens exhibits self-healing properties that are immune to scattering by particles and that it also possesses a larger depth of focus than a traditional metalens. Our results pave the way to the realization of flat photonic devices for applications to noninvasive biomedical imaging and light-sheet microscopy, and we provide a numerical demonstration of a device protocol.

Abstract-Broadband achromatic metalens in terahertz regime

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.