Temperature‐Controlled and Photoexcited Multitasking Janus Metasurface in the Terahertz Region

• Published in: Annalen der Physik Vol. 534; no. 5
• Main Authors: Guo, Zi‐Han, Sun, Yuan‐Zhe, Zeng, Li, Zhang, Hai‐Feng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-05-2022
• Subjects: Conversion ratio; Electric fields; Electromagnetic radiation; Germanium; Janus metasurfaces; Metasurfaces; Multitasking; multitasking devices; photoexcited materials; Photosensitivity; Polarization; polarization conversion; temperature‐controlled features; Vanadium dioxide
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.202100499

In this paper, a photoexcited multitasking Janus metasurface (MJM) based on the phase‐changed material vanadium dioxide and the photosensitive materials silicon and germanium in the terahertz (THz) region is proposed, which also exploits the directionality feature of electromagnetic waves. The MJM can switch its functionalities between working band shifting and full‐space polarized wave control, and six functions can be implemented by exciting the switchable materials. By regulating the power of the incident pump beam, it is feasible to complete band adjustment in terms of normal incidence, i.e. the band range of polarization conversion ratio >0.9 changing from 1.23 THz–1.91 THz to 0.98 THz–1.91 THz in the reflection state and axial ratio (AR) <3 dB band range toggling between 0.69 THz–1.08 THz and 0.67 THz–0.96 THz in the transmission state. However, for the backward incidence,, it presents reflective linear‐to‐circle (LTC) polarization conversion (PC), with AR <3 dB domain of 0.99 THz–1.63 THz. The multiple reflection interference theory and electric field distributions are introduced to interpret the high performance. Moreover, the designed device exhibits a high angular tolerance for achieving LTC PC. The integration of numerous functions in a single structure endows the MJM with the great benefit for efficient polarization‐controlled applications.
Tunable linear‐to‐circle (LTC) polarization conversion (PC) switches working band between 0.69–1.08 THz and 0.67–0.96 THz for normal incidence. In the reflection state, the operating band of the linear‐to‐linear PC changes from 1.23–1.91 THz to 0.98–1.91 THz. For backward incidence, it presents LTC PC with effective domain of 0.99–1.63 THz.