Multifunctional Metasurface Research Articles

Broadband high-efficiency multiple vortex beams generated by an interleaved geometric-phase multifunctional metasurface

Broadband high-efficiency multiple vortex beams generated by an interleaved geometric-phase multifunctional metasurface

Multifunctional Beam Manipulation at Telecommunication Wavelengths Enabled by an All‐Dielectric Metasurface Doublet

AbstractMultifunctional metasurfaces, which are planar devices featuring diverse functionalities, have attracted tremendous attention as they enable highly dense integration and miniaturization of photonic devices. Previous approaches based on spatial/spectral multiplexing of meta‐atoms on single metasurfaces are supposed to be inevitably limited in their functional diversity. An additional degree of freedom for design, achieved by cascading multiple metasurfaces into a single metasystem, promotes new combinations of functions that cannot be achieved with single‐layered metasurfaces. In this study, an all‐dielectric metasurface doublet (MD) is developed and implemented by vertically concatenating two arrays of rectangular nanoresonators on either side of a quartz substrate, in which distinct phase profiles are encoded for transverse magnetic and transverse electric polarized light. Multifunctional beam manipulation with concurrent increased beam deflection, beam reduction, and polarizing beam splitting is achieved at telecommunication wavelengths near 1550 nm. The MD is accurately created via lithographical nanofabrication, thus eliminating the extremely demanding post‐fabrication alignment. The proposed multifunctional metasurface is highly anticipated to expedite the development of advanced technologies for large‐scale photonic integration, optical metrology, light detection and ranging, spectroscopy, and optical processing.

Multifunctional polarization converting metasurface and its application to reduce the radar cross-section of an isolated MIMO antenna

This paper presents a wideband metasurface, based on polarization conversion operation and its application for the radar cross-section (RCS) reduction of an isolated MIMO antenna. The wideband metasurface is capable of converting linear polarization to orthogonal and circular polarizations. Linear polarization conversion is achieved over a wideband frequency range of 7.6–9.0 GHz. Whereas, linear-to-circular polarization is achieved in two different bands, from 7.10 to 7.40 GHz and 9.20 to 9.45 GHz. The RCS reduction is accomplished by destructive interference of the scattered waves, through the two sides of the designed metasurface. RCS reduction is achieved from 7.6 GHz to 8.6 GHz, with a maximum reduction of −32 dB at 7.6 GHz. To validate the RCS reduction, the polarization conversion metasurface is integrated with the isolated MIMO antenna working from 8.0–8.6 GHz, with high isolation of −25 dB. The radiation characteristics of the MIMO antenna are well preserved. The proposed integrated metasurface MIMO antenna is experimentally validated to verify the simulated results.

Dispersion engineering method results in multifunctional metasurfaces

Controlling the geometric design of the nanostructures in a metasurface leads to increased manipulation of the functionalities of metalenses.

Magnetically controlled multifunctional membrane acoustic metasurface

Acoustic artificial structures have attracted great interest due to their unique capacity in manipulating acoustic waves. Among them, acoustic metasurfaces are highlighted for tuning acoustic waves in the subwavelength scale, which is expected for realizing acoustic device miniaturization. However, traditional acoustic metasurfaces are passive and non-multifunctional, which limits their further practical applications. In this paper, a magnetically controlled approach is investigated for achieving a multifunctional acoustic metasurface. The properties of the proposed acoustic metasurface, consisting of elastic films and additional mass, could be continuously modulated by magnetic force. Through switching the magnetic forces, the transmitted acoustic wave is easily tailored and different functions such as focusing, beam-splitting-like, and other near-field acoustic displays are switched. This work extends the research of multifunctional metasurfaces and has excellent potential in a wide range of applications including acoustic imaging, communications, and particle manipulation (such as suspension and acoustic tweezers).

Controlling dispersion in multifunctional metasurfaces

Metasurfaces can be designed to exhibit different functionalities with incident wavelength, polarization, or angles through appropriate choice and design of the constituent nanostructures. As a proof-of-concept, we design and simulate three multifunctional metalenses with vastly different focal lengths at blue and red wavelengths to show that the wavelength dependence of focal length shift can be engineered to exhibit achromatic, refractive, or diffractive behavior. In addition, we design a metalens capable of achromatically focusing an incident plane wave to a spot and a vortex at red and blue wavelengths, respectively. These metalenses are designed with coupled subwavelength-scale dielectric TiO2 nanostructures. Our method illustrates a more general design strategy for multifunctional metasurfaces by considering phase and group delay profiles with applications in imaging, spectroscopy, and wearable optical devices.

Electro-optically Tunable Multifunctional Metasurfaces.

Shaping the flow of light at the nanoscale has been a grand challenge for nanophotonics over decades. It is now widely recognized that metasurfaces represent a chip-scale nanophotonics array technology capable of comprehensively controlling the wavefront of light via appropriately configuring subwavelength antenna elements. Here, we demonstrate a reconfigurable metasurface that is multifunctional, i.e., notionally capable of providing diverse optical functions in the telecommunication wavelength regime, using a single compact, lightweight, electronically controlled array with no moving parts. By electro-optical control of the phase of the scattered light from each identical individual metasurface element in an array, we demonstrate a single prototype multifunctional programmable metasurface that is capable of both dynamic beam steering and reconfigurable light focusing. Reconfigurable multifunctional metasurfaces with arrays of tunable optical antennas thus can perform arbitrary optical functions by programmable array-level control of scattered light phase, amplitude, and polarization, similar to dynamic and programmable memories in electronics.

Simultaneous Full-Color Printing and Holography Enabled by Centimeter-Scale Plasmonic Metasurfaces.

Optical metasurfaces enable novel ways to locally manipulate light's amplitude, phase, and polarization, underpinning a newly viable technology for applications, such as high‐density optical storage, holography, and displays. Here, a high‐security‐level platform enabled by centimeter‐scale plasmonic metasurfaces with full‐color, high‐purity, and enhanced‐information‐capacity properties is proposed. Multiple types of independent information can be embedded into a single metamark using full parameters of light, including amplitude, phase, and polarization. Under incoherent white light, the metamark appears as a polarization‐ and angle‐encoded full‐color image with flexibly controlled hue, saturation, and brightness, while switching to multiwavelength holograms under coherent laser illumination. More importantly, for actual applications, the extremely shallow functional layer makes such centimeter‐scale plasmonic metamarks suitable for cost‐effective mass production processes. Considering these superior performances of the presented multifunctional plasmonic metasurfaces, this work may find wide applications in anticounterfeiting, information security, high‐density optical storage, and so forth.

Dual‐band multifunctional metasurface for absorption and polarization conversion

In this paper, a multifunctional metasurface capable of switching between an absorber and a polarization converter is presented. The active metasurface comprises diamond-shaped unit cells embedded with PIN diodes. The characteristic of the design lies in its capability of exhibiting multifunctionality at the same frequency of operation. The structure behaves as an absorber and linear polarization converter around 15 and 17 GHz when the PIN diode is switched ON and OFF, respectively. The working principle is demonstrated with the help of simulated results. Finally, the design is fabricated and measured, and it is seen that the results are in accordance with that of the simulated ones, establishing the concept behind switchability of absorber and polarization converter.

Metasurfaces for Terahertz Wavefront Modulation: a Review

Metasurface is an artificial material composed of a series of subwavelength structure units and has unique electromagnetic characteristics. Based on the ability of manipulating the phase, amplitude, and polarization of electromagnetic wave, various kinds of metasurfaces are designed to realize wavefront manipulations, such as beam focusing, beam steering, vector beams generating, and holographic imaging. This paper reviews the design methods of metasurfaces for wavefront modulation and evolution of the metasurfaces designed for wavefront manipulation in the terahertz (THz) region. The metasurfaces can be divided into two categories: passive and active metasurfaces. For the passive metasurfaces, the single-functional metasurfaces, multifunctional metasurfaces, and high diffraction efficient metasurfaces designed for various THz wavefront shaping, such as focusing, imaging, and special beams generating, are reviewed. For the active metasurfaces, the metasurfaces with fixed structure and all-optical metasurfaces without fixed structure for THz wavefront modulation are summarized. Furthermore, a comparison on the performance of different kinds of metasurfaces for THz wavefront modulation is presented and the development direction and challenges of the THz wavefront modulation metasurfaces in the future are discussed.

Scaling down quantitative phase imaging

Quantitative phase gradient images can now be captured in a single shot thanks to the use of two layers of compact, multifunctional dielectric metasurfaces.

Multifunctional 2.5D metastructures enabled by adjoint optimization

Optical metasurfaces are two-dimensional arrays of meta-atoms that modify different characteristics of light such as phase, amplitude, and polarization. One intriguing feature that distinguishes them from conventional optical components is their multifunctional capability. However, multifunctional metasurfaces with efficiencies approaching those of their single-functional counterparts require more degrees of freedom. Here we show that 2.5D metastructures, which are stacked layers of interacting metasurface layers, provide sufficient degrees of freedom to implement efficient multifunctional devices. The large number of design parameters and their intricate intercoupling make the design of multifunctional 2.5D metastructures a complex task, and unit-cell approaches to metasurface design produce suboptimal devices. We address this issue by designing 2.5D metastructures using the adjoint optimization technique. Instead of designing unit cells individually, our technique considers the structure as a whole, accurately accounting for inter-post and inter-layer coupling. As proof of concept, we experimentally demonstrate a double-wavelength metastructure, designed using adjoint optimization, that has significantly higher efficiencies than a similar device designed with a simplified approach conventionally used in metasurface design. The 2.5D metastructure architecture empowered by the optimization-based design technique is a general platform for realizing high-performance multifunctional components and systems.

Switchable multifunctional fish-bone elastic metasurface for transmitted plate wave modulation

In this paper, a switchable multifunctional elastic metasurface is proposed to manipulate the transmitted plate waves. The flexural-dominated plate wave mode is concerned. The subwavelength functional unit of the designed metasurface looks like a “fish-bone” structure with nuts as vibrators. The positions of the nuts can be tuned continuously by screwing in or out, changing the phase shift in a full 2π span with high transmission. The tunability of the phase shift is demonstrated both numerically and experimentally, and can be interpreted by the dispersion properties of the wave propagating through the fish-bone like functional unit. Finally, according to the generalized Snell's law, broadband switches of an elastic metasurface between several functions including the directional refraction, wave focusing and beam self-bending are simulated numerically by just screwing in or out the nuts (vibrators).

融合计算全息术与纳米印刷术的多功能超表面研究进展

Computer-generated holography and nanoprinting are two typical applications of optical metasurfaces. Recently, merging holography and nanoprinting into a multifunctional metasurface becomes an emerging research hotspot, which has prospective applications in multi-folded anti-counterfeiting, information decoding and multiplexing, multi-channel image display and VR/AR, etc. In this paper, based on the features of metasurface-based nanoprinting and computer-generated holography, the advances in the research of merging them were classified and characterized in detail. Specifically, the merging methods were discussed in detail which included orthogonal-polarization multiplexing scheme, in-plane arrangement scheme, multilayer-stacking scheme, simultaneous spectrum and phase control scheme, complex amplitude modulation scheme, orientation degeneracy scheme. The future development of multifunctional metasurfaces was prospected.

Programmable anisotropic digital metasurface for independent manipulation of dual-polarized THz waves based on a voltage-controlled phase transition of VO2microwires

A THz reprogrammable anisotropic digital metasurface based on a VO2phase transition.

融合计算全息术与纳米印刷术的多功能超表面研究进展

融合计算全息术与纳米印刷术的多功能超表面研究进展

Reconfigurable Multifunctional Metasurface for Broadband Polarization Conversion and Perfect Absorption

A reconfigurable multifunctional metasurface is proposed to realize the switching between broadband polarization conversion and perfect absorption by integrating the PIN diodes into the structure. An appropriate feed plate is designed to provide the bias voltage that controls the state of the diodes. When the diodes are in off-state, the metasurface will work in polarization conversion mode, which can convert the co-polarization wave into its cross-polarization state with polarization conversion ratio (PCR) of over 90% in the range from 2.97 to 6.03 GHz; While the diodes are in on-state, the metasurface exhibits perfect absorption with absorptivity of over 90% from 2.56 to 7.62 GHz, and the relative absorption bandwidth (RAB) reaches 99.4%. In addition, the metasurface is fabricated and measured to confirm the multifunctional performance. The proposed metasurface is expected to be applied in electromagnetic detection, stealth technology and communication system.

In situ steering of shear horizontal waves in a plate by a tunable electromechanical resonant elastic metasurface

A multifunctional electromechanical coupling metasurface is proposed to steer elastic shear horizontal (SH) waves. The horizontal shear deformation of the metasurface is coupled with a shunting circuit by in-plane polarized piezoelectric patches. A prospective phase distribution along the metasurface can be achieved by adjusting the negative capacitances of the shunting circuit to change the electromechanical resonant response. Multiple functions are demonstrated, including wave focusing and anomalous refraction of plane waves in different frequencies. In addition, an asymmetric wave transmission is produced by designing a dual-layer metasurface. Results show that this metasurface opens up a way toward advanced electromechanical coupling and tunable manipulation of elastic SH waves.

Multifunctional elastic metasurface design with topology optimization

Metasurfaces have emerged as promising materials for wave manipulation due to their compact form. While various innovative designs have been proposed and impressive wave-shaping capabilities have been demonstrated, the practical applications of these materials require additional features and functionalities such as high-energy transmission and robust manipulation, which are difficult to realize based on physics-driven design approaches. In this work, we propose a systematic design method based on topology optimization for the design of elastic metasurfaces with multiple objectives/requirements. Theoretical analyses were conducted to identify the conditions for achieving high transmission and robust manipulation. Based on the analyses, a topology optimization formulation is proposed for achieving specific phase delays and high transmission within a given frequency band. Genetic algorithm is adopted to solve the optimization problem, with special treatments on the structural connectivity. Both locally resonant and non-resonant structures can be obtained from this method, and there is no need to pre-determine the type of structures to be designed. Depending on the design emphasis and the working frequency range, the proposed design method can automatically determine the best type of structures that meet the design requirements. With this method, metasurfaces for anomalous refraction of longitudinal waves were designed. Nearly full transmission with robust performance has been confirmed by numerical simulations. To demonstrate the generality of the proposed method, a multi-functional metasurface for simultaneously control of longitudinal and shear waves has also been designed, which is the first realization of such functionality.

Optimized chemical potential graphene-based coding metasurface approach for dynamic manipulation of terahertz wavefront

In this paper, a new method for the design of pixelated graphene-based coding metasurface is proposed. This method suggests a straightforward approach by utilizing graphene tunable pixels (GTPs), which can control the reflection phase in a real-time manner at terahertz (THz) frequencies. The proposed unit cell is composed of four distinct graphene patches in the same layer, which has a separate DC bias source. Each meta-atom can change the reflection phase by choosing appropriate chemical potential that obtained by utilizing optimization-based methods. By changing the reflection phase profile across the metasurface, the proposed device can manipulate the reflected wave dynamically. To investigate our proposed structure, we present a multifunctional reconfigurable metasurface to manipulate electromagnetic (EM) wave in the half-space and generate converged vortex beam, non-diffractive Bessel beam, and EM bump illusion. The simulation and theoretical results show that the suggested method offers a feasible strategy for multifunctional metasurface applications. Chemical potential optimization method in graphene-based coding metasurface is not limited to a specific structure for phase-only metasurface. Indeed it has an unique capability for phase, amplitude, and polarization control in various beamforming applications at THz spectrum for modern information systems, data encryption, and THz communication applications.