Polarization-Insensitive Magnetic Quadrupole-Shaped and Electric Quadrupole-Shaped Fano Resonances Based on a Plasmonic Composite Structure

A combined structure with the unit cell consisting of four sub-units with 90° rotation in turn is designed. Each of sub-units is composed of two gold rods in transverse arrangement and one gold rod in longitudinal arrangement. Simulating electromagnetic responses of the structure, we verify that the structure exhibits the double Fano resonances, which originate from the coupling between magnetic quadrupoles and electric dipoles and the coupling between electric quadrupoles and electric dipoles. Simulation results also demonstrate that the structure is polarization-insensitive and shows an analogue of electromagnetically induced transparency at the two Fano resonances. Such a plasmonic structure has potential applications in photoelectric elements.

A Polarization-Insensitive Broadband Metamaterial Absorber at the Optical Regime

We present a polarization-insensitive broadband absorber which has a feature of metal-insulator-metal structures. The top metal layer consists of four-fan-rings-shaped gold. Simulations show that the absorber exhibits an absorption of nearly unity at the wavelength of 386.1 nm and a relative absorption bandwidth of 0.548, which refers to the ratio of the full absorption bandwidth over an absorption of 0.9 to the central wavelength. Meanwhile, the absorption is nearly independent of the polarized direction of the incident wave. This absorption bandwidth with insensitive polarization is widely reported to date for such metal-insulator-metal structures. Such a structure offers a way of realization of a polarization-insensitive broadband absorber ranging in ultraviolet-to-visible wavelengths.

Ultra-compact and broadband polarization-insensitive mode-order converting power splitter

A polarization-insensitive mode-order converting power splitter using a pixelated region is presented and investigated in this paper.As TE_(0)and TM_(0)modes are injected into the input port,they are converted into TE_(1)and TM_(1)modes,which evenly come out from the two output ports.The finite-difference time-domain method and direct-binary-search optimization algorithm are utilized to optimize structural parameters of the pixelated region to attain small insertion loss,low crosstalk,wide bandwidth,excellent power uniformity,polarization-insensitive property,and compact size.Experimental results reveal that the insertion loss,crosstalk,and power uniformity of the fabricated device at 1550 nm are 0.57,-19.67,and 0.094 d B in the case of TE polarization,while in the TM polarization,the relevant insertion loss,crosstalk,and power uniformity are 0.57,-19.40,and 0.11 d B.Within a wavelength range from 1520 to 1600 nm,for the fabricated device working at TE polarization,the insertion loss,crosstalk,and power uniformity are lower than 1.39,-17.64,and 0.14 dB.In the case of TM polarization,we achieved an insertion loss,crosstalk,and power uniformity less than 1.23,-17.62,and 0.14 dB.

An ultra-compact polarization-insensitive slot-strip mode converter

Integrated waveguides with slot structures have attracted increasing attention due to their advantages of tight mode confinement and strong light-matter interaction.Although extensively studied,the issue of mode mismatch with other strip waveguide-based optical devices is a huge challenge that prevents integrated waveguides from being widely utilized in large-scale photonic-based circuits.In this paper,we demonstrate an ultra-compact low-loss slot-strip converter with polarization insensitivity based on the multimode interference(MMI)effect.Sleek sinusoidal profiles are adopted to allow for smooth connection between the slot and strip waveguide,resulting reflection reduction.By manipulating the MMI effect with structure optimization,the self-imaging positions of the TE0 and TM0 modes are aligned with minimized footprint,leading to low-loss transmission for both polarizations.The measurement results show that high coupling efficiencies of−0.40 and−0.64 dB are achieved for TE_(0) and TM_(0) polarizations,respectively.The device has dimensions as small as 1.1μm×1.2μm and composed of factory-available structures.The above characteristics of our proposed compact slot-strip converter makes it a promising device for future deployment in multi-functional integrated photonics systems.

Polarization-Insensitive All-Optical Time-Division Demultiplexer Constructed with a Nonlinear Loop Interferometer

A polarization-insensitive 40-Gb/s time-division demultiplexer was demonstrated in a polarization-diversity loop configuration. The power penalty was measured to be 2.3 dB at a bit error rates of 10-9 for 10 Gb/s output signals.

Polarization-Insensitive Hybrid Plasmonic Waveguide Design for Evanescent Field Absorption Gas Sensor

We propose a polarization-insensitive design of a hybrid plasmonic waveguide(HPWG)optimized at the 3.392µm wavelength which corresponds to the absorption line of methane gas.The waveguide design is capable of providing high mode sensitivity(Smode)and evanescent field ratio(EFR)for both transverse electric(TE)and transverse magnetic(TM)hybrid modes.The modal analysis of the waveguide is performed via 2-dimension(2D)and 3-dimension(3D)finite element methods(FEMs).At optimized waveguide parameters,Smode and EFR of 0.94 and 0.704,can be obtained for the TE hybrid mode,respectively,whereas the TM hybrid mode can offer Smode and EFR of 0.86 and 0.67,respectively.The TE and TM hybrid modes power dissipation of~3 dB can be obtained for a 20-µm-long hybrid plasmonic waveguide at the 60%gas concentration.We believe that the highly sensitive waveguide scheme proposed in this work overcomes the limitation of the polarization controlled light and can be utilized in gas sensing applications.

Cut-wire metasurface embedded in magnetic mediums for ultra-wideband polarization-insensitive absorber with environmental adaptability

Metamaterials with artificial designability and perfect absorption provide a novel design method for the manipulation and attenuation of microwaves.However,owing to the limitations of meta-atomic reso-nance effect and the lossless medium,it is difficult to achieve effective microwave absorption in a broad-band frequency range.Hence,an ultra-wideband metamaterial absorber(UWMA)composed of two mag-netic media and a metasurface was designed,and the absorption bandwidth of 2.9 to 18 GHz for 90%absorptivity under normal incidence was achieved,covering almost the entire S,C,X,and Ku bands.Through detailed investigation of equivalent circuit,equivalent medium theory,electromagnetic field dis-tribution and front-back interface interference,the internal physical working mechanism was clarified essentially.In addition,the multi-environment adaptabilities of the proposed absorber,including polariza-tion sensitivity,large angle incidence,dual-station radar stealth,bearing capacity and corrosion resistance,were analyzed.The proposed metamaterial absorber presents an effective way to achieve ultra-wideband absorption and compatibility with environmental adaptability,and provides a new way of thinking for intelligent full-band stealth technology.

Ultra-high extinction-ratio light modulation by electrically tunable metasurface using dual epsilon-near-zero resonances

The lossy nature of indium tin oxide(ITO) at epsilon-near-zero(ENZ) wavelength is used to design an electrically tunable metasurface absorber. The metasurface unit cell is constructed of a circular resonator comprising two ITO discs and a high dielectric constant perovskite barium strontium titanate(BST) film. The ENZ wavelength in the accumulation and depletion layers of ITO discs is controlled by applying a single bias voltage. The coupling of magnetic dipole resonance with the ENZ wavelength inside the accumulation layer of ITO film causes total absorption of reflected light. The reflection amplitude can achieve ~84 d B or ~99.99% modulation depth in the operation wavelength of 820 nm at a bias voltage of-2.5 V. Moreover, the metasurface is insensitive to the polarization of the incident light due to the circular design of resonators and the symmetrical design of bias connections.