Electrically tunable transmission of gold binary-grating metasurfaces integrated with liquid crystals

Double-Resolved Beam Steering by Metagrating-Based Tamm Plasmon Polariton

We consider Tamm plasmon polariton in a subwavelength grating patterned on top of a Bragg reflector. We demonstrate dynamic control of the phase and amplitude of a plane wave reflected from such metagrating due to resonant coupling with the Tamm plasmon polariton. The tunability of the phase and amplitude of the reflected wave arises from modulation of the refractive index of a transparent conductive oxide layer by applying the bias voltage. The electrical switching of diffracted beams of the ±1st order is shown. The possibility of doubling the angular resolution of beam steering by using asymmetric reflected phase distribution with integer and half-integer periods of the metagrating is demonstrated.

Active optical metasurfaces: comprehensive review on physics, mechanisms, and prospective applications

Optical metasurfaces with subwavelength thickness hold considerable promise for future advances in fundamental optics and novel optical applications due to their unprecedented ability to control the phase, amplitude, and polarization of transmitted, reflected, and diffracted light. Introducing active functionalities to optical metasurfaces is an essential step to the development of next-generation flat optical components and devices. During the last few years, many attempts have been made to develop tunable optical metasurfaces with dynamic control of optical properties (e.g., amplitude, phase, polarization, spatial/spectral/temporal responses) and early-stage device functions (e.g., beam steering, tunable focusing, tunable color filters/absorber, dynamic hologram, etc) based on a variety of novel active materials and tunable mechanisms. These recently-developed active metasurfaces show significant promise for practical applications, but significant challenges still remain. In this review, a comprehensive overview of recently-reported tunable metasurfaces is provided which focuses on the ten major tunable metasurface mechanisms. For each type of mechanism, the performance metrics on the reported tunable metasurface are outlined, and the capabilities/limitations of each mechanism and its potential for various photonic applications are compared and summarized. This review concludes with discussion of several prospective applications, emerging technologies, and research directions based on the use of tunable optical metasurfaces. We anticipate significant new advances when the tunable mechanisms are further developed in the coming years.

Design and Simulation of Active Frequency-selective Metasurface for Full-colour Plasmonic Display

In this paper, we report a full-colour plasmonic pixel by incorporating a low-index buffer layer and an EO material layer with a gap surface plasmon-based metasuface. The reflection spectra can be modulated by an external voltage bias with a reflectivity higher than 60% when filtering red, green and blue primary light. Vivid colour can be generated by mixing the three primaries in time sequence. Brightness can be tuned by the duty cycle of bright and dark state. Theoretical calculations demonstrate that the switchable pixels we designed can achieve a gamut overlapping 80% area of NTSC colour space and a contrast ratio of 10.63, 26.11 and 2.97 for red, green and blue when using a white quatom-dot-enhancement-film backlit.

Achieving a tunable metasurface based on a structurally reconfigurable array using SMA

We introduce a structurally reconfigurable metasurface which is made of shape memory alloys (SMA). It could change the morphology of the unit cells repeatedly as we expect in response to a thermal stimulus and realize a tuning range from 13.3GHz to 17.2GHz for both polarizations simultaneously. Equivalent circuit models describe the operational principle and design methodology, the physical mechanism is interpreted with the variation of surface current distribution on the structure. The experimental results coincide with the numerical simulations, making the all-metal metasurface an attractive choice for manipulating the electromagnetic wave in a wide range of spectrums with the merits of higher controllability for dynamic behavior and greater freedom for design and manufacturing.

Liquid-crystal tunable color filters based on aluminum metasurfaces

Designing color pixels using plasmonic nanostructures and metasurfaces has become a luring area of research in recent years. Here, we experimentally demonstrated the voltage tunability of a dynamic plasmonic color filter by using an aluminum grating integrated with the nematic liquid crystal (LC). Along with a typical substrate coated with rubbed polyimide film, the aluminum grating itself serves as a molecular alignment layer to form a twisted LC cell. This hybrid structure allows electrically controlled transmission color by applying the voltage. A significant spectral tunability of such a device has been demonstrated by applying the small voltage from 0 to 4 V_rms.

Electrically Tunable Gap Surface Plasmon-based Metasurface for Visible Light

In this paper, an electrically tunable metasuface is designed for visible regime. The device mainly consists of a V-shaped metallic metasurface, an ITO film, an electro-optic (EO) dielectric and a metal layer fabricated on a silica substrate. A continuous electrical modulation of resonant wavelength has been theoretically demonstrated in the visible range from 555 nm to 640 nm by changing the voltage applied on the EO dielectric from -20 V to 20 V. During the modulation, the steering angle also changes with the selective color. The peak cross-polarized reflectivity is higher than 48% and the bandwidth is narrower than 60 nm. The resonant wavelength shift can be explained by that the refractive index variation of the EO material induces resonance condition changes of the gap surface plasmon (GSP). The results provide a novel design solution for active plasmonic devices, especially for dynamic metadevices.