Universal active metasurfaces for dynamic beam steering and reconfigurable focusing at telecommunication wavelengths

We report the design and experimental demonstration of a ‘universal’ reconfigurable metasurface, which by electrical control of individual metasurface elements, enables both dynamic beam steering and reconfigurable focusing

Universal active metasurfaces for dynamic beam steering and reconfigurable focusing at telecommunication wavelengths

We report the design and experimental demonstration of a ‘universal’ reconfigurable metasurface, which by electrical control of individual metasurface elements, enables both dynamic beam steering and reconfigurable focusing

Tunable all-dielectric metasurface for phase modulation of the reflected and transmitted light via permittivity tuning of indium tin oxide

We propose an electrically tunable metasurface, which can achieve relatively large phase modulation in both reflection and transmission modes (dual-mode operation). By integration of an ultrathin layer of indium tin oxide (ITO) as an electro-optically tunable material into a semiconductor-insulator-semiconductor (SIS) unit cell, we report an approach for active tuning of all-dielectric metasurfaces. The proposed controllable dual-mode metasurface includes an array of silicon (Si) nanodisks connected together via Si nanobars. These are placed on top of alumina and ITO layers, followed by a Si slab and a silica substrate. The required optical resonances are separately excited by Si nanobars in reflection and Si nanodisks in transmission, enabling highly confined electromagnetic fields at the ITO-alumina interface. Modulation of charge carrier concentration and refractive index in the ITO accumulation layer by varying the applied bias voltage leads to 240° of phase agility at an operating wavelength of 1696 nm for the reflected transverse electric (TE)-polarized beam and 270° of phase shift at 1563 nm for the transmitted transverse magnetic (TM)-polarized light. Independent and isolated control of the reflection and transmission modes enables distinctly different functions to be achieved for each operation mode. A rigorous coupled electrical and optical model is employed to characterize the carrier distributions in ITO and Si under applied bias and to accurately assess the voltage-dependent effects of inhomogeneous carrier profiles on the optical behavior of a unit cell

Array-Level Inverse Design of Beam Steering Active Metasurfaces

We report an array-level inverse design approach to optimize the beam steering performance of active metasurfaces, thus overcoming the limitations posed by nonideal metasurface phase and amplitude tuning. In contrast to device-level topology optimization of passive metasurfaces, the outlined system-level optimization framework relies on the electrical tunability of geometrically identical nanoantennas, enabling the design of active antenna arrays with variable spatial phase and amplitude profiles. Based on this method, we demonstrate high-directivity, continuous beam steering up to 70° for phased arrays with realistic tunable antenna designs, despite nonidealities such as strong covariation of scattered light amplitude with phase. Nonintuitive array phase and amplitude profiles further facilitate beam steering with a phase modulation range as low as 180°. Furthermore, we use the device geometries presented in this work for experimental validation of the system-level inverse design approach of active beam steering metasurfaces. The proposed method offers a framework to optimize nanophotonic structures at the array level that is potentially applicable to a wide variety of objective functions and actively tunable metasurface antenna array platforms

Array-scale inverse design of active metasurfaces

We develop an inverse design approach to optimize array architectures of reconfigurable metasurfaces and report dramatically improved beam steering performances with non-ideal antenna components. The versatility is enhanced by enabling continuous steering up to 70°

All-dielectric multiple quantum well active metasurfaces

We report a design of an all-dielectric Mie-resonant active metasurface, which exhibits a high reflectance (>45%) and a broad tunable phase shift at an operation wavelength of 1550 nm. The proposed design can be used for the realization of two-dimensional active metasurfaces

Emitter-Metasurface Interface for Manipulating Emission Characteristics of Quantum Defects

We demonstrate a chip-scale quantum emitter-metamaterial device that emits highly directional photons. Our device opens the door for quantum imaging of yveak sources by adding photon(s) to manipulate the photon statistics for improved signal-to-noise ratio

Emitter-Metasurface Interface for Manipulating Emission Characteristics of Quantum Defects

We demonstrate a chip-scale quantum emitter-metamaterial device that emits highly directional photons. Our device opens the door for quantum imaging of yveak sources by adding photon(s) to manipulate the photon statistics for improved signal-to-noise ratio