Xiaobin Hu

High efficiency broadband −90° to 90° arbitrary optical rotation realized with meta reflectarray

We theoretically demonstrate high efficiency broadband -90° to 90° arbitrary optical rotation realized with meta reflectarray composed of a L-shaped silver antenna array, a silica spacer, and a silver ground plane. Co-polarized and cross-polarized components of reflected wave can be manipulated efficiently by adjusting arm length of the L-shaped antenna, and 0° to 90° arbitrary optical rotation with high degree of linear polarization (DoLP) over a broadband can be achieved readily. The phase of cross-polarized field component can be reversed by turning the L-shaped antennas upside down, and 0° to 90° optical rotation can be turned into 0° to -90° rotation. Reflected phase can be shift by π after a 90° rotation of the L-shaped or Γ-shaped antennas, while optical rotation angle remains the same. Thus, rotation angle θ is changed to 180° + θ after the rotation, and we realized 0° to 360° polarization rotation with a step of 60° with the combination of six discrete structure units. In addition, we proposed metamaterial structures for highly efficient generation of vector beams with these units. The high efficiency broadband arbitrary angle optical rotation will profoundly affect a wide range of applications involving optical polarization.

Metallic metasurfaces for high efficient polarization conversion control in transmission mode

A high efficient broadband polarization converter is an important component in integrated miniaturized optical systems, but its performances is often restricted by the material structures, metallic metasurfaces for polarization control in transmission mode never achieved efficiency above 0.5. Herein, we theoretically demonstrate that metallic metasurfaces constructed by thick cross-shaped particles can realize a high efficient polarization transformation over a broadband. We investigated the resonant properties of designed matesurfaces and found that the interaction between double FP cavity resonances and double bulk magnetic resonances is the main reason to generate a high transmissivity over a broadband. In addition, through using four resonances effect and tuning the anisotropic optical response, we realized a high efficient (> 0.85) quarter-wave plate at the wavelength range from 1175nm to 1310nm and a high efficient (> 0.9) half-wave plate at the wavelength range from 1130nm to 1230nm. The proposed polarization converters may have many potential applications in integrated polarization conversion devices and optical data storage systems.

Realization of circularly polarized beam based on plasmonic metasurface

We present a quarter-wave plate composed of two pairs of cross-shaped elliptical nanoatennas. This setup can transform linearly polarized incident light to circular polarized light at a wavelength of 862nm. The cross-shaped elliptical configuration can control the amplitude and phase of incident light. By the modulation of the elliptical size, equal amplitude and specific phase difference can be obtained in orthogonal directions. Furthermore, as a quarter-wave plate, this configuration is not sensitive to the polarized direction of the linearly polarized incident beam. In order to verify the designed metasurface, numerical simulation were performed using the finite difference time domain method. Our results may benefit novel photonics devices design such as polarization manipulation, optical sensing, optical detecting, and photonic integration.

Resonant cavity enhanced waveguide transmission for broadband and high efficiency quarter-wave plate

Existing transmission type optical quarter-wave plates based on metallic sub-wavelength structures can hardly realize transmission efficiency above 60%. And their working bandwidths are still very narrow. In this paper, we demonstrate a transmission type quarter-wave plate design with efficiency above 92% over a broad wavelength range (from 1260 nm to 1560 nm). The device proposed is based on a one-dimensional metal-insulator-metal waveguide array buried in silica. Phase difference between transmitted TE and TM components can be tuned continuously. At the same time, transmission efficiency can be kept above 90% in the same spectral range for both the TE and TM incidences. The broad bandwidth and remarkable efficiency are explained with the combination of low dispersion of waveguide modes and the resonant cavity enhanced transmission effect. To give a better understanding of the structure, we also propose a modified effective medium model. The optical response of the structure can be well reproduced with the semi-analytic effective medium model.

0∘ to 90∘ arbitrary controllable optical activity with an array of L-shaped silver holes inside a silica cube

We realize high efficiency 0–90∘ arbitrary polarization rotation by using a single layer of L-shaped silver hole array inside a silica cube. The simulation results show that the 0–90∘ arbitrary polarization rotation can be manipulated easily by adjusting the arm length of L-shaped holes, and the degree of linear polarization (DoLP) of the transmission spectra can achieve high over all range of 0–90∘. Our design has been optimized for 1550 nm wavelength. This arbitrary polarization rotation plasmonic metamaterial may provide more possibilities for applications in photonics.

Generation of vector beams with polarization rotation metasurfaces

We theoretically demonstrate high efficiency broadband vector beams generation with polarization rotation metasurfaces composed of L-shaped silver antenna array, silica spacer, and silver ground plane. 0° to 90° arbitrary optical rotation with high degree of linear polarization (DoLP) over a broadband can be achieved readily by adjusting arm length of the L-shaped antenna. And through turning the L-shaped antennas upside down, the 0° to 90° optical rotation can be turned into 0° to -90°. Reflected phase can be shift by π after a 90° rotation of the L-shaped or Γ-shaped antennas, while optical rotation angle remains the same. Then six discrete units are designed to realize 0° to 360° polarization rotation with a step of 60°. With the combination of these units, we proposed metamaterial structures for highly efficient generation of radially polarized and azimuthally polarized vector beams.

Investigation of polarization-selective InGaAs sensor with elliptical two-dimensional holes array structure

Polarimetric imaging in infrared wavelengths have attracted more and more attention for broad applications in meteorological observations, medicine, remote sensing and many other fields. Metal metamaterial structures are used in nanophotonics in order to localize and enhance the incident electromagnetic field. Here we develop an elliptical gold Two-Dimensional Holes Array (2DHA) in which photons can be manipulated by surface plasmon resonance, and the ellipse introduce the asymmetry to realize a polarization selective function. Strong polarization dependence is observed in the simulated transmission spectra. To further understand the coupling mechanism between gold holes array and InP, the different parameters of the 2DHA are analyzed. It is shown that the polarization axis is perpendicular to the major axis of the ellipse, and the degree of polarization is determined by the aspect ratio of the ellipse. Furthermore, the resonance frequency of the 2DHA shows a linear dependence on the array period, the bandwidth of transmission spectra closely related to duty cycle of the ellipse in each period. This result will establish a basis for the development of innovative polarization selective infrared sensor.