Independent Phase Control in Gap‐Tuned Metasurfaces for Dual‐Function Switching

• Published in: Laser & photonics reviews Vol. 18; no. 10
• Main Authors: Liao, Yi, Chen, Kaiji, Su, Xiaoqiang, Xu, Quan, Niu, Li, Wu, Tong, Zhang, Huifang, Gu, Jianqiang, Zhang, Xueqian
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.10.2024
• Subjects: Angular momentum; Circular polarization; Control equipment; Controllability; dual‐function switching; dynamic phase; gap‐tuned metasurface; independent phase control; Metasurfaces; Pancharatnam–Berry phase; Phase control; Switching (polarity); Wave front control; Wave fronts
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.202400100

Seeking new ways to actively control the phase using metasurfaces has gained significant attention in recent years, which is the key to achieve controllable wavefronts under external stimuli. Among various active phase control mechanisms, a mechanical method based on gap tuning, termed as gap‐tuned metasurface here, has shown promise in continuous phase adjustment. However, previous studies face limitations in independent and complete phase control at different gap distances, which is crucial in dual‐function switching applications. In this study, a novel type of gap‐tuned metasurfaces are proposed, which can overcome the above limitations through simultaneously manipulating the Pancharatnam–Berry phase and gap‐induced dynamic phase under circularly polarized incidences. Two exemplary gap‐tuned metasurfaces capable of orbital angular momentum (OAM) switching and focusing‐polarity switching are experimentally demonstrated. Furthermore, the special dynamic phase design also exhibits phase conjugate property similar to the Pancharatnam–Berry phase, making circular polarization handedness an alternative route for dual‐function switching. This method provides a straightforward and effective means for the development of active wavefront control devices. A novel mechanical method for achieving dual‐function switching is proposed using gap‐tuned metasurfaces. The special design allows independent control over the reflection phases and wavefronts at two gap states through manipulating Pancharatnam–Berry phase and dynamic phase. Two metasurfaces capable of switching orbital angular momentum and focusing polarity are presented. This method offers a robust pathway to realize dynamic devices.