Hyperbolic Metamaterial Devices for Wavefront Manipulation

Abstract

Metasurfaces have shown great potential to reshape the wavefront of electromagnetic (EM) waves, but transmissive meta-devices face challenges of low-efficiency and/or fabrication complexities. Here, an alternative approach to realize high-efficiency transmission-mode meta-devices to control EM wavefronts, based on hyperbolic metamaterial (HMM) waveguides supporting tailored spoof surface plasmons (SSPs) on their side walls, is proposed. By manipulating the dispersions of SSPs through adjusting the HMM geometrical parameters, the phases of EM waves passing through such waveguides, which enables the design of meta-devices with desired transmission-phase profiles for particular wave-manipulation applications, can be controlled. Microwave experiments are implemented to demonstrate two wave-control effects based on the mechanism, that is, beam-deflection and focusing, and a maximum conversion efficiency of 42.9% is achieved for the anomalous refracted beam. By scaling down the HMM meta-devices, the proposal herein is applicable to optical frequencies and in principle promises significantly raised conversion efficiencies. The scheme herein can offer a higher effective refractive index and more tunable dispersion without using high-index dielectric materials, and thus can serve as an effective and robust approach to make high-efficiency transmissive meta-devices with diversified functionalities.approach to the extreme control of EM waves, leading to a variety of intriguing phenomena and applications that are unattainable with natural materials such as negative refraction, [4] super-resolution imaging, [5] and invisibility cloaking. [6] As the 2D equivalent of metamaterials, metasurfaces have shown great promises to control EM waves by locally modulating the phase, amplitude and/or polarization of the scattered field. [7][8][9][10][11][12][13] Distinct from traditional photonic devices (e.g., lenses) that rely on propagation phases accumulated inside the device to shape the wavefront, metasurfaces utilize the interfacial phase discontinuities introduced by subwavelength-sized planar resonators to locally control the amplitude and phase of scattered waves and thus to reshape the wavefront of EM waves. Many fascinating wave-manipulation effects were discovered based on metasurfaces, such as light bending, [7,11,13] unidirectional surface plasmon coupling, [8,14] invisibility cloaks, [6,15] flat lenses, [9,16] holography, [17,18] and generation of vortex beam. [7,19] Transmissive metasurfaces are particularly useful in practice, but the working efficiencies of single-layer plasmonic metasurfaces are typically low. For example, a single-layer Pancharatnam-Berry (PB) metasurface, working for circularly polarized (CP) light, cannot exhibit an efficiency higher than 25%, due to

Empowered Layer Effects and Prominent Properties in Few‐Layer Metasurfaces

“…Although these limits can be partially resolved by using thicker dielectric structures, these structures always need relatively larger size compared with plasmonic structures and have limited degrees of freedom to control the phase. However, few‐layer metasurfaces can easily realize high‐efficiency transmission and cover the full 2π phase range . In addition, the few‐layer metasurfaces can provide more degrees of freedom to manipulate the phase.…”

Reconfigurable continuous-zoom metalens in visible band

“…(6). It is because of the coupling effect among adjacent nanobricks and finite aperture of the metalens [38,39], such deviation will decrease as the mutual rotation angle θ increases or say the focal length decreases. Although the simulated focal plane is not at an ideal place, it does not affect the zoom functionality of a large range since the mutual rotation angle θ is reconfigurable and all the simulation results show that the metalens can focus light well.…”

Mode-resolved directional enhancement of spontaneous emission inside/outside finite multilayer hyperbolic metamaterials

“…Hyperbolic Metamaterials (HMMs) hold promise to embody the boundless possibilities in light-matter interaction on nanoscale [1]. Artificial materials having hyperbolic dispersion have been designed for various applications such as nano focusing [2], sensing [3,4], wave front manipulation [5], sub diffraction imaging [6,7], emission enhancement of quantum emitters [8,9] and many more. HMMs have attracted a great attention for spontaneous emission enhancement due to the large photonic Local Density of States (LDOS) associated with their unique modes having large wave vector, so called highk modes [10,11].…”