Metasurface-based flat lens have great potentials for applications in compact and portable cameras. However, the properties of optical metasurfaces are strongly limited by the intrinsic ohmic loss of metal and the fixed working distance. Here, we propose a highly efficient all-dielectric metasurface lens working in near-infrared frequency range. By exploiting silicon nanoblock as meta-atoms, the silicon metasurface produces phase changes covering 0 to 2π and near-unity reflection, inducing the focusing of light over a broad wavelength range. Interestingly, the focal length of such an ultrathin flat lens can be dynamically controlled by incorporating tunable materials such as liquid crystals. By utilizing the phase transition or electrical alignment of liquid crystals, the focal length has been tuned up to 10 %. We believe our research will be important to accelerate the applications of optical metasurfaces.
A class of 45 • linearly polarized and circular polarized high scanning rate leaky wave antennas are proposed in this paper, which is based on slow-wave substrate integrated waveguide structure. High scanning rate leaky wave antennas have recently become attractive for imaging applications and automotive radar. These applications also require a continuous scanning range without an open stopband, as seen at broadside for ordinary leaky wave antennas. Furthermore, both 45 • linearly polarization and circularly polarization are required in practical applications. In this paper, we propose an all-in-one leaky wave antenna design, which features high scanning rate, continuous scanning capability across the broadside, 45 • linear polarization or circularly polarization, single-layer configuration, and single-side radiation. Two design examples are provided to illustrate the proposed principle. Both simulation and experimental validation are given.
INDEX TERMSLeaky wave antenna, substrate integrated waveguide, scanning rate, open stopband, linear polarization, circular polarization.
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