Polarization insensitivity electromagnetically induced reflection in graphene metasurface

The electromagnetically induced reflection(EIR)effect of graphene metamaterials has been investigated by finite difference time domain(FDTD)method.In this study,a metamaterial sandwich structure composed of silica(SiO2),gold and graphene on terahertz band is designed.By changing the width of the two ribbons of graphene length and the incident angle of electromagnetic wave,the EIR effect of the structure is discussed,and it can be found that SiO2 is a kind of excellent dielectric material.The simulation results show that graphene metamaterial is not sensitive to polarized incident electromagnetic wave.Therefore,such EIR phenomena as insensitive polarization and large incident angle can be applied to optical communication filters and terahertz devices.

Polarization Insensitivity in Double-Split Ring and Triple-Split Ring Terahertz Resonators

A modified double-split ring resonator and a modified triple-split ring resonator, which offer polarization-insensitive performance, are investigated, designed and fabricated. By displacing the two gaps of the conventional double- split ring resonator away from the center, the second resonant frequency for the 0° polarized wave and the resonant frequency for the 90° polarized wave become increasingly close to each other until they are finally identical. Theoretical and experimental results show that the modified double-split ring resonator and the modified triple-split ring resonator are insensitive to different polarized waves and show strong resonant frequency dips near 433 and 444OHz, respectively. The results of this work suggest new opportunities for the investigation and design of polarization-dependent terahertz devices based on split ring resonators.

Polarization insensitivity in square split-ring resonators with asymmetrical arm widths

A polarization-insensitive, square split-ring resonator（SSRR） is simulated and experimented. By investigating the influence of the asymmetrical arm width in typical SSRRs, we find that the variation of the arm width enables a blue shift of the resonance frequency for the 0° polarized wave and a red shift of the resonance frequency for the 90° polarized wave. Thus, the resonance frequency for the 0° polarized wave and the resonance frequency for the 90° polarized wave will be identical by asymmetrically adjusting the arm width of the SSRR. Two modified, split-ring resonators（MSRRs） that are insensitive to the polarization with asymmetrical arm widths are designed, fabricated, and tested. Excellent agreement between the simulations and experiments for the MSRRs demonstrates the polarization insensitivity with asymmetrical arm widths. This work opens new opportunities for the investigation of polarization-insensitive, split-ring resonator metamaterials and will broaden the applications of split-ring resonators in various terahertz devices.

1550nm Polarization-Insensitive Semiconductor Optical Amplifier Based on AlGaInAs-InP

Polarization insensitive AlGaInAs InP semiconductor optical amplifier is realized at a wavelength of 1550nm.The active layer consists of three tensile strained wells with strain 0 40%.The amplifiers are fabricated to ridge waveguide structure with 7° tilted cavity.The two facets are coated with two layers of anti reflection Ti 3O 5/Al 2O 3 films.Residual facet reflectivity is found to be less than 0 03%.The semiconductor optical amplifer exhibits 20dB of signal gain and 7 2dBm of saturation output power with an excellent polarization insensitivity (less than 0 8dB) at 200mA and 1540nm window.

Wide-Band Polarization-Independent Semiconductor Optical Amplifier Gate with Tensile-Strained Quasi-Bulk InGaAs

A semiconductor optical amplifier gate based on tensile strained quasi bulk InGaAs is developed.At injection current of 80mA,a 3dB optical bandwidth of more than 85nm is achieved due to dominant band filling effect.Moreover,the most important is that very low polarization dependence of gain (<0 7dB),fiber to fiber lossless operation current (70～90mA) and a high extinction ratio (>50dB) are simultaneously obtained over this wide 3dB optical bandwidth (1520～1609nm) which nearly covers the spectral region of the whole C band (1525～1565nm) and the whole L band (1570～1610nm).The gating time is also improved by decreasing carrier lifetime.The wide band polarization insensitive SOA gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

Polarization Insensitive Broadband Zero Indexed Nano-Meta Absorber for Optical Region Applications

Broadband response metamaterial absorber(MMA)remains a challenge among researchers.A nanostructured new zero-indexed metamaterial(ZIM)absorber is presented in this study,constructed with a hexagonal shape resonator for optical region applications.The design consists of a resonator and dielectric layers made with tungsten and quartz(Fused).The proposed absorbent exhibits average absorption of more than 0.8972(89.72%)within the visible wavelength of 450–600 nm and nearly perfect absorption of 0.99(99%)at 461.61 nm.Based on computational analysis,the proposed absorber can be characterized as ZIM.The developments of ZIM absorbers have demonstrated plasmonic resonance characteristics and a perfect impedance match.The incidence obliquity in typically the range of 0◦–90◦both in TE and TM mode with maximum absorbance is more than 0.8972(∼89.72%),and up to 45◦angular stability is suitable for solar cell applications,like exploiting solar energy.The proposed structure prototype is designed and simulated by studying microwave technology numerical computer simulation(CST)tools.The finite integration technique(FIT)based simulator CST and finite element method(FEM)based simulator HFSS also helps validate the numerical data of the proposed ZIM absorber.The proposed MMA design is appropriate for substantial absorption,wide-angle stability,absolute invisible layers,magnetic resonance imaging(MRI),color images,and thermal imaging applications.

Graphene-Based Tunable Polarization Insensitive Dual-Band Metamaterial Absorber at Mid-Infrared Frequencies

A graphene-based tunable dual-band metamaterial absorber which is polarization insensitive is numerically pro- posed at mid-infrared frequencies. In numerical simulation the metamaterial absorber exhibits two absorption peaks at the resonance wavelengths of 6.246 μm and 6.837μm when the Fermi level of graphene is fixed at 0. 6 eV. Absorption spectra at different Fermi levels of graphene are displayed and tuning functions are discussed in detail. Both the resonance wavelengths of the absorber blue shift with the increase in Fermi level of graphene. Moreover, the surface current distributions on the gold resonator and ground plane at the two resonance wavelengths are simulated to deeply understand the physical mechanism of resonance absorption.

Broadband visible light absorber based on ultrathin semiconductor nanostructures

It is desirable to have electromagnetic wave absorbers with ultrathin structural thickness and broader spectral absorption bandwidth with numerous applications in optoelectronics.In this paper,we theoretically propose and numerically demonstrate a novel ultrathin nanostructure absorber composed of semiconductor nanoring array and a uniform gold substrate.The results show that the absorption covers the entire visible light region,achieving an average absorption rate more than 90%in a wavelength range from 300 nm to 740 nm and a nearly perfect absorption from 450 nm to 500 nm,and the polarization insensitivity performance is particularly great.The absorption performance is mainly caused by the electrical resonance and magnetic resonance of semiconductor nanoring array as well as the field coupling effects.Our designed broadband visible light absorber has wide application prospects in the fields of thermal photovoltaics and photodetectors.

Polarization insensitive arrayed-input spectrometer chip based on silicon-on-insulator echelle grating

Imaging spectrometers are most commonly used on satel- lites and aircrafts, including unmanned aerial vehicles （UAVs）, where the spare volume and weight are limited.