All-dielectric optical metasurfaces represent a new platform that is able to change electromagnetic field dramatically, while having thickness much smaller than the optical wavelength. The properties of metasurface depends critically on the geometry of its nanostructuring, therefore they are pre-set during the fabrication process. However, a number of practical application of such metasurfaces requires the dynamic change of their properties with operation. Embedding the metasurface in LC we can offer unique opportunities for such tuning and control of their properties. Here we show that by applying voltage across the LC or by varying its temperature we are able to control the spectral position of the metasurface’s electric and magnetic resonances. Using this method, we demonstrate experimentally the tuning of the properties of homogeneous metasurface consisted from array of equal elements as well as switch on and off different metasurface devices that use nanostructures with gradient geometries.
In particular, we show that applying voltage across the LC cell (one substrate of which is a Si disk metasurface), we can change the spectral position of electric and magnetic resonances thus changing intensity and phase of transmitted electromagnetic wave. To demonstrate possibility of thermal controlling of metasurface with special geometry, we further utilize gradient metasurface that deflect light beams. By heating the LC to the critical temperature we can switch the transmitted beam from straight propagation to angular deflection. Overall, by combining developed LC technologies with the emerging field of nanostructured metasurfaces we show the potential for novel ultra-thin tunable optical devices.
Andrei Komar, Zheng Fang, Isabelle Staude, Manuel Decker, Andrey E. Miroshnichenko, Justus Bohn, Ramon Paniagua Dominguez, Ye Feng Yu, Arseniy I. Kuznetsov, Yuri S. Kivshar, and Dragomir N. Neshev, "Liquid-crystal tunable metasurfaces for phase modulation and beam deflection (Conference Presentation)," Proc. SPIE 10113, High Contrast Metastructures VI, 1011316 (Presented at SPIE OPTO: February 03, 2017; Published: 28 April 2017); https://doi.org/10.1117/12.2251767.5395679960001.
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