Tunable Photonic Metasurfaces: Fundamentals and Applications

Photonic metasurfaces—two-dimensional arrangements of resonant nanoparticles with designer optical responses—have emerged as a game-changer in the field of flat optics [1,2]. However, most metasurfaces exhibit fixed properties after fabrication, and adding tunability expands vastly the scope of the metasurface use scenarios. Here, we review our recent results in metasurfaces tunable at various time scales, from seconds to femtoseconds; see Fig. 1. We start by using liquid crystals as switching agents for metalenses with electrically actuated focal spots at low (&lt; 10 V) voltages and high focal spot tunability [3]. The second part of the talk demonstrates pico- and femtosecond-scale tuning in semiconductor metasurfaces that provide an ultrafast platform for all-optical information processing [4]. Finally, we outline the potential use of tunable metasurfaces in polarization synthesizers, nonlinear and quantum optics, and frequency conversion on demand [5,6].<br/>References<br/>[1] Kildishev, A. V.; Boltasseva, A.; Shalaev, V. M. Planar photonics with metasurfaces. Science 2013, 339, 1232009.<br/>[2] Yu, N.; Capasso, F. Flat optics with designer metasurfaces. Nat. Mater. 2014, 13, 139−150.<br/>[3] Bosch, M.; Shcherbakov, M. R.; Won, K.; Lee, H.-S.; Kim, Y.; Shvets, G. Electrically Actuated Varifocal Lens Based on Liquid-Crystal- Embedded Dielectric Metasurfaces, Nano Lett. 2021, 21, 3849−3856.<br/>[4] Shcherbakov, M. R. et al. Ultrafast all-optical tuning of direct-gap semiconductor metasurfaces, Nat. Commun. 2017, 8, 17.<br/>[5] Karl, N. et al. Frequency Conversion in a Time-Variant Dielectric Metasurface, Nano Lett. 2020, 20, 10, 7052–7058.<br/>[6] Bosch, M.; Shcherbakov, M. R.; Fan, Z.; Shvets, G. Polarization states synthesizer based on a thermo-optic dielectric metasurface, J. Appl. Phys. 2019, 126, 073102.