Metasurfaces are an emerging platform for manipulating light on a two-dimensional plane. Existing metasurfaces comprise arrays of optical resonators such as plasmonic antennas or high-index nanorods. In this letter, we describe a new approach to realize metasurfaces based on electronic transitions in two-level systems (TLSs). These metasurfaces can reproduce all of the major results in conventional metasurfaces. In addition, since TLSs can be lossless, tunable, and orders of magnitude smaller than optical resonators, atomic metasurfaces can realize functions that are difficult to achieve with optical resonators. Specifically, we develop quantum scattering theory to describe the interaction between single photons and atomic metasurfaces. Based on the theory, we use a sheet of three-level Λ-type atoms as an example and theoretically demonstrate dynamically tunable single-photon steering. We further show directional beaming of spontaneously emitted photons from atomic metasurfaces.
Metasurfaces are two-dimensional optical structures enabling complete control of the amplitude, phase, and polarization of light. Unlike plasmonic metasurfaces, planar silicon structures facilitate high transmission, low losses and compatibility with existing semiconductor technologies. Here, we report an experimental demonstration of high-efficiency polarization- sensitive dielectric metasurfaces with full 2pi phase control in transmission mode at telecommunication wavelengths. Such silicon metasurfaces are poised to enable a versatile optical platform the realization of all-optical circuitry…
We show that a metasurface-coated two-dimensional (2D) slab waveguide enables the generation of arbitrary complex light fields by combining the extreme versatility and freedom on wavefront control of optical metasurfaces with the compactness of photonic integrated circuits. We demonstrated off-chip 2D focusing and holographic projection with our metasurface-dressed photonic integrated devices. This technology holds the potential for many other optical applications requiring 2D light field manipulation with full on-chip integration, such as solid-state LiDAR and near-eye AR/VR displays.
The manipulation of visible light is important in science and technology research. Metasurfaces can enable flexible and effective regulation of the phase, polarization, and propagation modes of an electromagnetic wave. Metasurfaces have become a research hotspot in optics and electromagnetics, and cross-polarization conversion is an important application for visible-light manipulation using a metasurface. A metasurface composed of nano-antenna arrays and bilayer plasma can reportedly convert the direction of linear polarized light efficiently. However, the metasurface of cross-polarization con…
A hybrid plasmonic-dielectric metasurface is proposed in order to manipulate beam propagation in desired manners. The metasurface is composed of patterned hybrid graphene-silicon nano-disks deposited on a low-index substrate, namely silica. It is shown that the proposed hybrid metasurface simultaneously benefits from the advantages of graphene-based metasurfaces and dielectric ones. Specially, we show that the proposed hybrid metasurface not only provides reconfigurability, just like previously proposed graphene-based metasurfaces, but also similar to dielectric metasurfaces it is low loss and…
The possibility of integration of two important categories of optical components, i.e., circular polarizer and lens, into a thin plasmonic metasurface is examined. After exploring general theoretical formulation, optimal designs to realize polarizing lenses at mid-infrared frequencies are presented, for the cases when metal losses cannot be neglected. A two-dimensional array of Y-shaped nanoantennas with polarization dependent and spatially varying phase response is the basis for such a unique compact polarizing lens, whose properties can have a high impact in integrated optics.
With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modeling a metasurface as time-varying admittance sheets, we provide an analytical calculation method to predict the metasurface time-domain responses. This allows derivation of design specifications in the form of equivalent sheet admittance, which is usef…
In recent years, optical vortex beams possessing orbital angular momentum have caught much attention due to their potential for high capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provides infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile …
We conceptualized three-array scalable metasurfaces comprising only three thin strip grids and numerically demonstrated their characteristics in the mid-infrared spectral regime for switchable polarization manipulation and related asymmetric diodelike transmission (AT). A few or all of the grids were taken to be made of VO$_2$, a phase-change material. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO$_2$. The achieved scenarios of functionality switching that depend on the VO$_…
Manipulating the polarization of light is highly desired for versatile applications ranging from super resolution, optical trapping, to particle acceleration. The enormous freedom in metasurface design motivates the implementation of polarization control in ultrathin and compact optical systems. However, the majority of proposed strategies based on metasurfaces have been demonstrated only a spatially homogeneous polarization generation, while less attention has been devoted to spatially variant inhomogeneous vector beams. Here, we demonstrate a novel method for generating arbitrary radial and …
Nonlinear wavefront control is a crucial requirement in realizing nonlinear optical applications with metasurfaces. Numerous aspects of nonlinear frequency conversion and wavefront control have been demonstrated for plasmonic metasurfaces. However, several disadvantages limit their applicability in nonlinear nanophotonics, including high dissipative loss and low optical damage threshold. In contrast, it has been shown that metasurfaces made of high-index dielectrics can provide strong nonlinear responses. Regardless of the recent progress in nonlinear optical processes using all-dielectric nan…
We develop an analytical framework for self-stabilizing optical manipulation of freestanding metasurfaces in three dimensions. Our framework reveals that the challenging problem of stabilization against translational and rotational perturbations in three dimensions is reduced to a simpler scattering analysis of the metasurface unit cell in two dimensions. We derive universal analytical stiffness coefficients applicable to arbitrary three-dimensional radial metasurfaces and radial beam intensity profiles. The analytical nature of our framework facilitates highly efficient discovery of optimal o…
Space-time modulated metasurfaces have attracted significant attention due to the additional degree of freedom in manipulating the electromagnetic (EM) waves in both space and time domains. However, the existing techniques have limited wave control capabilities, leading to just a few feasible schemes like regulation of only one specific harmonic. Here, we propose to realize independent manipulations of arbitrarily dual harmonics and their wave behaviors using a space-time-coding (STC) digital metasurface. By employing different STC sequences to the reflection phase of the metasurface, independ…
Auxiliary nanostructures introduce additional flexibility into optomechanical manipulation schemes. Metamaterials and metasurfaces capable to control electromagnetic interactions at the near-field regions are especially beneficial for achieving improved spatial localization of particles, reducing laser powers required for trapping, and for tailoring directivity of optical forces. Here, optical forces acting on small particles situated next to anisotropic substrates, are investigated. A special class of hyperbolic metasurfaces is considered in details and is shown to be beneficial for achieving…
Metasurfaces have shown unprecedented possibilities for wavefront manipulation of waves. The research efforts have been focused on the development of metasurfaces that perform a specific functionality for waves of one physical nature, for example, for electromagnetic waves. In this work, we propose the use of power-flow conformal metamirrors for creation of multiphysics devices which can simultaneously control waves of different nature. In particular, we introduce metasurface devices which perform specified operations on both electromagnetic and acoustic waves at the same time. Using a purely …
Vortex beams carrying orbital angular momentum (OAM) have been widely applied in various electromagnetic, optical, and quantum systems. A tailored OAM spectrum composed of several specific modes as expected holds a promise for expanding the degrees of freedom of the systems. However, such a broadband high-purity tailored spectrum is difficult to be achieved by the present devices, where the broadband amplitude manipulation has not been explored yet. In this work, inspired by the envelope-modulation theory, an elegant and universal way to manipulate the OAM spectrum in wide bandwidth is propose…
Faraday rotation is a fundamental magneto-optical phenomenon used in various optical control and magnetic field sensing techniques. Recently, it was shown that a giant Faraday rotation can be achieved in the low-THz regime by a single monoatomic graphene layer. Here, we demonstrate that this exceptional property can be manipulated through adequate nano-patterning, notably achieving giant rotation up to 6THz with features no smaller than 100nm. The effect of the periodic patterning on the Faraday rotation is predicted by a simple physical model, which is then verified and refined through accura…
On-chip mode-division multiplexing (MDM) has been emerging as a promising technology to further enhance the link capacity and bandwidth of data communications with multiple mode channels. Both mode converters and mode exchangers are indispensable fundamental components for flexible mode operations. While several configurations have been developed previously, it is still very challenging to efficiently manipulate arbitrary high-order modes in a versatile way to reduce the R&D and prototyping costs. Here we initiate a breakthrough with a simple yet universal generic mode operator building block …
Geballe Laboratory for Advanced Materials, Stanford University（斯坦福大学格巴尔先进材料实验室）
Metasurface-based optical elements typically manipulate light waves by imparting space-variant changes in the amplitude and phase with a dense array of scattering nanostructures. The highly-localized and low optical-quality-factor (Q) modes of nanostructures are beneficial for wavefront-shaping as they afford quasi-local control over the electromagnetic fields. However, many emerging imaging, sensing, communication, display, and non-linear optics applications instead require flat, high-Q optical elements that provide notable energy storage and a much higher degree of spectral control over the …
Metasurfaces, composed of subwavelength scattering elements, have demonstrated remarkable control over the transmitted amplitude, phase, and polarization of light. However, manipulating the amplitude upon transmission has required loss if a single metasurface is used. Here, we describe high-efficiency independent manipulation of the amplitude and phase of a beam using two lossless phase-only metasurfaces separated by a distance. With this configuration, we experimentally demonstrate optical components such as combined beam-forming and splitting devices, as well as those for forming complex-val…
Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the nanoscale. Here we add a temporal gradient to the picture, showing that spatio-temporal variations over a surface may largely extend the degree of light manipulation in metasurfaces, and break several of their constraints associated to symmetries. As an example, we synthesize a non-reciprocal classical analogue to electromagnetic induced transparency, opening a narrow window of one-way transmission in an otherwise opaque surface. These properties pave th…
The strong interaction of light with micro- and nanostructures plays a critical role in optical sensing, nonlinear optics, active optical devices, and quantum optics. However, for wavefront shaping, the required local control over light at a subwavelength scale limits this interaction, typically leading to low-quality-factor optical devices. Here, we demonstrate an avenue towards high-quality-factor wavefront shaping in two spatial dimensions based on all-dielectric Huygens metasurfaces by leveraging higher-order Mie resonances. We design and experimentally realize transmissive band stop filte…
The optical elements comprised of sub-diffractive light scatterers, or metasurfaces, hold a promise to reduce the footprint and unfold new functionalities of optical devices. A particular interest is focused on metasurfaces for manipulation of phase and amplitude of light beams. Characterisation of metasurfaces can be performed using interferometry, which, however, may be cumbersome, specifically in the infrared (IR) range. Here, we realise a new method for characterising IR metasurfaces based on nonlinear interference, which uses accessible components for visible light. Correlated IR and visi…
Metasurfaces enable manipulation of light propagation at an unprecedented level, benefitting from a number of merits unavailable to conventional optical elements, such as ultracompactness, precise phase and polarization control at deep subwavelength scale, and multifunctionalities. Recent progress in this field has witnessed a plethora of functional metasurfaces, ranging from lenses and vortex beam generation to holography. However, research endeavors have been mainly devoted to static devices, exploiting only a glimpse of opportunities that metasurfaces can offer. We demonstrate a dynamic met…
Metasurfaces composed of planar arrays of sub-wavelength artificial structures show promise for extraordinary light manipulation; they have yielded novel ultrathin optical components such as flat lenses, wave plates, holographic surfaces and orbital angular momentum manipulation and detection over a broad range of electromagnetic spectrum. However the optical properties of metasurfaces developed to date do not allow for versatile tunability of reflected or transmitted wave amplitude and phase after fabrication, thus limiting their use in a wide range of applications. Here, we experimentally de…
Plasma-state metasurfaces for ultra-intensive field manipulation
College of Physics, Sichuan University（四川大学物理学院）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；School of Optics and Photonics, Beijing Institute of Technology（北京理工大学光电学院）；University of Hong Kong（香港大学）；Chinese Academy of Sciences（中国科学院）
Metasurfaces enable flat optical elements by leveraging optical resonances in metallic or dielectric nanoparticles to obtain accurate control over the amplitude and phase of the scattered light. While highly efficient, these resonances are static and difficult to tune actively. Exciton resonances in atomically thin 2D semiconductors provide a novel and uniquely strong resonant light-matter interaction, which presents a new opportunity for optical metasurfaces. Their resonant properties are intrinsic to the band structure of the material and do not rely on nanoscale patterns and are highly tuna…
The recently proposed extreme-ultraviolet (EUV) beams with time-varying orbital angular momentum (OAM) realized by high-harmonic generation (HHG) provides extraordinary tools for quantum excitation control and particle manipulation. However, such an approach is not easily scalable to other frequency regimes. Here, we design a space-time-coding digital metasurface operating in microwave frequencies to experimentally generate different modes of time-varying OAM. We also introduce a concept of superhelicity of time-varying OAM with a higher-order twist of the wavefront structure, which can be fur…
Control of the phase and polarization states of light is an important goal for nearly all optical research. The development of an efficient optical component that allows the simultaneous manipulation of the polarization and phase distribution is needed. Traditional methods require the combination of multiple optical devices, and a single optical device cannot easily realize full control of light. We theoretically predict and experimentally verify that our proposed dual-metasurfaces provide an excellent means to simultaneously manipulate the phase and polarization of transmission light at the n…
Metasurface holograms are typically fabricated on rigid substrates. Here we experimentally demonstrate broadband, flexible, conformable, helicity multiplexed metasurface holograms operating in the visible range, offering increased potential for real life out-of-the-lab applications. Two symmetrically distributed holographic images are obtained when circularly polarized light impinges on the reflective-type metasurface positioned on non- planar targets. The two off-axis images with high fidelity are interchangeable by controlling the helicity of incident light. Our metasurface features the arra…
Metalenses, which exhibit superior light-modulating performance with sub-micrometer-scale thicknesses, are suitable alternatives to conventional bulky refractive lenses. However, fabrication limitations, such as a high cost, low throughput, and small patterning area, hinder their mass production. Here, we demonstrate the mass production of low-cost, high-throughput, and large-aperture visible metalenses using an argon fluoride immersion scanner and wafer-scale nanoimprint lithography. Once a 12-inch master stamp is imprinted, hundreds of centimeter-scale metalenses can be fabricated. To enhanc…
Metasurfaces offer unprecedented flexibility in the design and control of light propagation, replacing bulk optical components and exhibiting exotic optical effects. One of the basic properties of the metasurfaces, which renders them as frequency selective surfaces, is the ability to transmit or reflect radiation within a narrow spectral band that can be engineered on demand. Here we introduce and demonstrate experimentally in the THz domain the concept of wavevector selective surfaces -- metasurfaces transparent only within a narrow range of light propagation directions operating effectively …
A full (2$π$) phase modulation is critical for efficient wavefront manipulation. In this article, a metasurface based on graphene long/short-strip resonators is used to implement a dynamic 2$π$ phase modulation by applying different voltages to different graphene resonators. The configuration is found to have high reflection efficiency (minimum 56%) and has a full phase modulation in a wide frequency range. Terahertz (THz) beam steering as large as 120 degrees ($\pm60^\circ$) is demonstrated in a broad frequency range (1.2 to 1.9 THz) by changing the Fermi levels of different graphene resonato…
Ultracold atom arrays in optical lattices emerge as an excellent playground for the integration of topological photonics and quantum optics. Here, we study high-order topological quantum optics in an ultracold atom metasurface intended to mimic the two-dimensional Su-Schrieffer-Heeger model. We find the existence of long-range interactions beyond nearest-neighbor ones leads to isolated corner states in the band gap, and show a corner atom can be addressed by a laser drive far away from it via these nontrivial states. We demonstrate the Purcell factor can be used as a powerful tool to examine t…
As two-dimensional metamaterials, metasurfaces open up new avenues for designing static planar optics. However, the dynamic modulation of metasurfaces in the optical band is required for practical applications. The existing dynamic devices rarely utilized the polarization manipulation capability of metasurfaces. Here, we demonstrate an electrically tunable multifunctional metasurface in the visible range by integrating birefringent liquid crystals (LCs) with all-dielectric metasurfaces based on a novel packaging scheme. By combining the helicity-dependent geometric phase of the metasurface and…
Designer manipulation of light at the nanoscale is key to several next-generation technologies, from sensing to optical computing. One way to manipulate light is to design a material structured at the sub-wavelength scale, a metamaterial, to have some desired scattering effect. Metamaterials typically have a very large number of geometric parameters that can be tuned, making the design process difficult. Existing design paradigms either neglect degrees of freedom or rely on numerically expensive full-wave simulations. In this work, we derive a simple semi-analytic method for designing metamate…
Here we make use of vanadium dioxide (VO2) to design a bifunctional metasurface working at the same targeted frequency. With the increase of temperature, the functionality of the designed metasurface can switch from a multi-channel retroreflector to a perfect absorber, caused by the phase transition of VO2 from insulator to conductor. Different from traditional bifunctional metasurfaces designed by simple composition of two functionalities, our proposed bifunctional metasurface is based on the interaction between two functionalities. The device shows good potential for the combination of wavef…
Optical metasurfaces have come into the spotlight as a promising platform for light manipulation at the nanoscale, including ultrafast all-optical control via excitation with femtosecond laser pulses. Recently, dichroic metasurfaces have been exploited to modulate the polarization state of light with unprecedented speed. Here, we theoretically predict and experimentally demonstrate by pump-probe spectroscopy the capability to reconfigure the ultrafast dichroic signal of a gold metasurface by simply acting on the polarization of the pump pulse, which is shown to reshape the spatio-temporal dist…
Femtosecond all-optical polarization manipulation of harmonic generation in an anisotropic strongly coupled plasmon-epsilon-near-zero metasurface
Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, School of Electronic Science and Engineering, Xi’an Jiaotong University（教育部光电技术与器件重点实验室、陕西省信息光子技术重点实验室，西安交通大学电子科学与工程学院）
