Design of Multifunctional Janus Metasurface Based on Subwavelength Grating

Low profile high gain RHCP antenna for L-Band and S-Band using rectangular ring metasurface with backlobe suppression

In this reported work a single feed, miniaturized, dual layer, and low profile antenna is presented for 1.575GHz frequency band. The proposed antenna offers high gain, lower noise bandwidth, with better sensitivity and range. The ground choke technique is used for back lobe suppression. The prototype is fabricated on FR 4 substrate using manual fabrication technique. This offers an inexpensive and readily available fabrication. Therefore, fabricated antenna is small size, low cost, easily fabricated and tested for satellite communication. The antenna comprises of two layers, containing a patch radiator and a Metasurface layer with 3x3 rectangular ring resonators. The layers are separated using foam with a 12mm width. The proposed prototype is radiating at 1.575GHz and 2.33GHz with an overall dimension of 85.6 x 68.4 x 15.204 mm. The developed antenna provides a gain of 5.9 dBi. The simulated results are verified using VNA and anechoic chamber testing. Moreover, the developed antenna has been successfully tested for L-Band Satellite communication in real time scenario without any LNA. Higher Gain due to Metasurface increase the efficiency of the system. The promising results indicate the aptness of the developed antenna for real-world applications of L-Band and S-Band.

Metasurface-based circular polarizer with a controllable phase and its application in holographic imaging

A diatomic circular polarizer based on a single-layered metasurface is proposed. This metasurface circular polarizer carries the controllable phase besides the desired circular dichroism, which is different from the existing circular polarizers. The diatoms contain two nanoholes equivalent to half-wave plates with a specified cross angle and a fixed phase difference. The alternative circular polarization transmission of this circular polarizer depends on the relative angular position of diatoms, and the controllable phase of this circular polarizer can be adjusted through rotating nanoholes. The generation of the optical vortex and holographic imaging verifies the polarization and phase manipulation of the diatomic circular polarizer. The numerical simulations and the experimental measurement give the powerful verification. Simple design, compact structure, and poly-functionality enable the wide applications of circular polarizer in integrated and polarized optics.

A Single-Celled Metasurface for Multipolarization Generation and Wavefront Manipulation

Due to their unprecedented ability to flexibly manipulate the parameters of light, metasurfaces offer a new approach to integrating multiple functions in a single optical element. In this paper, based on a single-celled metasurface composed of chiral umbrella-shaped metal-insulator-metal (MIM) unit cells, a strategy for simultaneous multiple polarization generation and wavefront shaping is proposed. The unit cells can function as broadband and high-performance polarization-preserving mirrors. In addition, by introducing a chiral-assisted Aharonov-Anandan (AA) geometric phase, the phase profile and phase retardation of two spin-flipped orthogonal circular polarized components can be realized simultaneously and independently with a single-celled metasurface via two irrelevant parameters. Benefiting from this flexible phase manipulation ability, a vectorial hologram generator and metalens array with spatially varying polarizations were demonstrated. This work provides an effective approach to avoid the pixel and efficiency losses caused by the intrinsic symmetry of the PB geometric phase, and it may play an important role in the miniaturization and integration of multipolarization-involved displays, real-time imaging, and spectroscopy systems.

Sub-wavelength patterned pulse laser lithography for efficient fabrication of large-area metasurfaces

Rigorously designed sub-micrometer structure arrays are widely used in metasurfaces for light modulation. One of the glaring restrictions is the unavailability of easily accessible fabrication methods to efficiently produce large-area and freely designed structure arrays with nanoscale resolution. We develop a patterned pulse laser lithography (PPLL) approach to create structure arrays with sub-wavelength feature resolution and periods from less than 1 μm to over 15 μm on large-area thin films with substrates under ambient conditions. Separated ultrafast laser pulses with patterned wavefront by quasi-binary phase masks rapidly create periodic ablated/modified structures by high-speed scanning. The gradient intensity boundary and circular polarization of the wavefront weaken diffraction and polarization-dependent asymmetricity effects during light propagation for high uniformity. Structural units of metasurfaces are obtained on metal and inorganic photoresist films, such as antennas, catenaries, and nanogratings. We demonstrate a large-area metasurface (10 × 10 mm²) revealing excellent infrared absorption (3–7 μm), which comprises 250,000 concentric rings and takes only 5 minutes to produce.

Fabrication of metasurfaces with nanoscale structures is inefficient for large areas. Here, the authors introduce patterned pulse laser lithography for creating structured arrays with sub-wavelength feature on large-area thin films under ambient conditions.

Multi-Band High-Efficiency Multi-Functional Polarization Controller Based on Terahertz Metasurface

Electromagnetic metasurfaces with excellent electromagnetic wave regulation properties are promising for designing high-performance polarization control devices, while the application prospect of electromagnetic metasurfaces is limited because of the current development situations of the complex structure, low conversion efficiency, and narrow working bandwidth. In this work, we design a type of reflective terahertz metasurface made of a simple structure that can achieve multiple polarization modulation with high efficiency. It is shown that the presented metasurface can realize ultra-broadband, cross-polarization conversion with the relative working bandwidth reaching 94% and a conversion efficiency of over 90%. In addition, the proposed metasurface can also efficiently accomplish different polarization conversion functions, such as linear-to-linear, linear-to-circular, or circular-to-linear polarization conversion in multiple frequency bands. Due to the excellent properties, the designed metasurface can be used as a high-efficiency multi-functional polarization modulation device, and it has important application value in terahertz imaging, communication, biological detection, and other fields.

Multifunctional Plasmonic Grating Based on the Phase Modulation of Excitation Light

Multifunctional optical devices are desirable at all times due to their features of flexibility and high efficiency. Based on the principle that the phase of excitation light can be transferred to the generated surface plasmon polaritons (SPPs), a plasmonic grating with three functions is proposed and numerically demonstrated. The Cherenkov SPPs wake or nondiffracting SPPs Bessel beam or focusing SPPs field can be correspondingly excited for the excitation light, which is modulated by a linear gradient phase or a symmetrical phase or a spherical phase, respectively. Moreover, the features of these functions such as the propagation direction of SPPs wake, the size and direction of the SPPs Bessel beam, and the position of SPPs focus can be dynamically manipulated. In consideration of the fact that no extra fabrication is required to obtain the different SPPs fields, the proposed approach can effectively reduce the cost in practical applications.

High-Performance Asymmetric Optical Transmission Based on a Dielectric-Metal Metasurface

Asymmetric optical transmission plays a key role in many optical systems. In this work, we propose and numerically demonstrate a dielectric-metal metasurface that can achieve high-performance asymmetric transmission for linearly polarized light in the near-infrared region. Most notably, it supports a forward transmittance peak (with a transmittance of 0.70) and a backward transmittance dip (with a transmittance of 0.07) at the same wavelength of 922 nm, which significantly enhances operation bandwidth and the contrast ratio between forward and backward transmittances. Mechanism analyses reveal that the forward transmittance peak is caused by the unidirectional excitation of surface plasmon polaritons and the first Kerker condition, whereas the backward transmittance dip is due to reflection from the metal film and a strong toroidal dipole response. Our work provides an alternative and simple way to obtain high-performance asymmetric transmission devices.

Spin-decoupled metasurface for broadband and pixel-saving polarization rotation and wavefront control

In this paper, a strategy to achieve a simultaneous wavefront shaping and polarization rotation, without compromising the number of pixels and energy efficiency as well as having broadband operation range, is proposed. This strategy is based on the application of a spin-decoupled phase metasurface composed by only one set of metal-insulator-metal (MIM) umbrella-shaped chiral unit cells. Quasi-non-dispersive and spin-decoupled phase shift can be achieved simply by changing single structural parameter of the structure. By further merging the Pancharatnam-Berry (PB) geometric phase, conversion of an incident LP light beam into right- and left-handed circularly polarized reflected beams with similar amplitudes, desired phase profiles and controlled phase retardation on a nanoscale is enabled with high efficiency. Based on the proposed strategy, a polarization-insensitive hologram generator with control optical activity, and a multiple ring vortex beam generator are realized. The results obtained in this work provide a simple and pixel-saving approach to the design of integratable and multitasking devices combining polarization manipulation and wavefront shaping functions, such as vectorial holographic generators, multifocal metalenses, and multichannel vector beam generators.