Manipulation Of Polarization State Research Articles

Optical Polarization Encoding Using Graphene‐Loaded Plasmonic Metasurfaces

Moreover, the development of a feasible metadevice design that has the ability to dynamically tune the light polarization state has attracted enormous interest. Such metadevices can be employed for realizing not only the polarization encoding but also polarization-division multiplexing (PDM), which is a crucial technique that can signifi cantly increase the transmission capacity of a single physical channel. [ 34 ] The traditional technique for realizing PDM requires a complex optical system and cumbersome volume. Therefore, a metadevice-based polarization modulator offers a new approach for simplifying the optical process and miniaturizing the required volume. Although metasurfaces can transform light polarization, the change of polarization-control characteristic requires variation of the size, shape, and material properties of the structure. Hence, the dynamical manipulation of the polarization state using a metasurface is still challenging. In this work, we propose a metadevice by integrating a single layer of graphene with an anisotropic metasurface, which can dynamically modulate the polarization state of light with wide tunable range in MIR wavelengths. By switching gate voltage applied on the graphene among three different values, the incident linearly polarized (LP) light can be dynamically converted into left circularly polarized (LCP) light, right circularly polarized (RCP) light, or linearly cross-polarized light in the refl ection direction by the proposed metadevice. A continuous polarization evolution from LCP to RCP light can be achieved as the gate voltage gradually increases. In addition, two mutually perpendicular LP light beams and an elliptically polarized (EP) light beam can also be generated in the refl ection direction by the proposed metadevice under EP light illumination. Based on these polarization-control characteristics, the proposed metadevice can realize polarization encoding and the PDM technique. The process of multiplexing and demultiplexing in the PDM technique can be accomplished by metadevices with a more simple approach and in a more compact space than traditional PDM techniques. The new degrees of freedom enabled by the metadevice facilitate the arbitrary manipulation of light polarization states and will profoundly affect a wide range of modern optical communication devices. Control of the light polarization state is an important area of research for metasurfaces. The anisotropy of plasmonic metasurfaces plays a dominant role in manipulating the light polarization state. The different optical responses along two orthogonal principal axes of the nanostructures result in different amplitude attenuation and phase retardation of the Optical Polarization Encoding Using Graphene-Loaded Plasmonic Metasurfaces

Peculiarities of Acoustooptic Transformation of Bessel Light Beams in Gyrotropic Crystals (*)

The peculiarities have been studied of acoustooptic (AO) diffraction of quasi- nondiffracting vector Bessel light beams (BLB) on the ultrasound waves in optical gyrotropic cubic crystals. The system of coupled equations describing the process of acoustooptic interaction is solved, diffraction efficiency has been calculated. The mathematical description of AO interaction, which differs from the similar description for the plane optical waves means of two types of synchronism, is conducted. It is shown that besides the usual longitudinal synchronism realized at the equality of phase velocities transmitted and diffracted waves, for Bessel beams it is also necessary to perform the so-called transverse synchronism. It is related with the fact, that Bessel beams with differing cone angles have different spatial structure and, consequently, various values of overlap integral with the input beam. The possibility has been investigated of transformation of the order of phase dislocation of Bessel beams wave front due to AO diffraction. It is proposed to use the process of acoustooptic diffraction in gyrotropic cubic crystals as a method for dynamic manipulation of polarization state of output Bessel beam, particularly for transformation of left- to right (and vice versa) polarization states.

Burst-mode manipulation of magnonic vortex crystals

The manipulation of polarization states in $4\ifmmode\times\else\texttimes\fi{}4$ vortex crystals using sinusoidal magnetic field bursts is investigated by means of a broadband ferromagnetic-resonance setup. Magnetic field excitation with the proper amplitude and frequency allows tuning different polarization states, which are observed in the measured absorption spectra. The variation of the sinusoidal burst width consecutively identifies the time scale of the underlying process. A memorylike polarization state writing process is demonstrated on the submicrosecond time scale.

Metallic stereostructured layer: An approach for broadband polarization state manipulation

In this letter, we report a full-metallic broadband wave plate assembled by standing metallic L-shaped stereostructures (LSSs). We show that with an array of LSSs, high polarization conversion ratio is achieved within a broad frequency band. Moreover, by rotating the orientation of the array of LSSs, the electric components of the reflection beam in two orthogonal directions and their phase difference can be independently tuned. In this way, all the polarization states on the Poincaré sphere can be realized. As examples, the functionalities of a quarter wave plate and a half wave plate are experimentally demonstrated with both reflection spectra and focal-plane-array imaging. Our designing provides a unique approach in realizing the broadband wave plate to manipulate the polarization state of light.

A perfect metamaterial polarization rotator

Polarization conveys valuable information for electromagnetic signal processing exhibiting tremendous potential in developing application driven photonic devices. Manipulation of polarization state of an electromagnetic wave has drawn a lot of research interests in many different fields, especially in the terahertz regime. Here, we propose a unique approach to efficiently rotate the linear polarization of terahertz wave in a broadband configuration with tri-layer metasurfaces. We experimentally observe a nearly perfect orthogonal polarization conversion with an ultrahigh efficiency, demonstrating a ultrathin terahetz rotator. The Fabry-Perot cavity effect in the tri-layer metasurfaces is attributed to the underlying mechanism of high transmittance and polarization rotation.

Topological spin-orbit interaction of light in anisotropic inhomogeneous subwavelength structures

Spin-orbit interaction resulting from spatial polarization state manipulation is demonstrated. Polarization-state manipulation is achieved by utilizing the effective birefringent nature of subwavelength structures acting as an anisotropic inhomogeneous medium. Experimental verification is obtained by measuring the effect of the unavoidable spin-dependent Pancharatnam-Berry phase modulation on the far-field diffraction pattern of the beam. Unlike the usual dynamic spin-orbit interaction that splits spin states in the temporal frequency (energy) domain, this topological spin-orbit interaction results in the splitting of spin states degenerated by their spatial frequencies (momentum).

Excitation of a single hollow waveguide mode using inhomogeneous anisotropic subwavelength structures

We propose and analyze a general approach for coupling a free space uniformly polarized beam to a desired hollow waveguide mode, thus enabling a single mode operation. The required spatial polarization state manipulation is achieved by use of inhomogeneous anisotropic subwavelength structures. Demonstration is obtained by coupling a linearly polarized CO(2) laser beam at a wavelength of 10.6 mum to the TE(01), TM(01), EH(11), EH(21), and EH(31) modes of a 300 mum diameter dielectric-coated hollow metallic waveguide. Full polarization and intensity analysis of the beam at the waveguide's inlet and outlet ports indicates a high coupling efficiency to a single waveguide mode. Finally, shaping the waveguide mode to a nearly diffraction limited linearly polarized beam and to a radially polarized vectorial vortex are also demonstrated.

Space-Variant Polarization-State Manipulation with Computer-Generated Subwavelength Gratings

Novel methods for space-variant polarization-state manipulation using subwavelength metal and dielectric gratings are presented. By locally controlling the period and direction of the grating, we show that any desired polarization can be achieved. The methods presented in this paper are generic to any portion of the spectrum, and we present experimental demonstrations of our theory using CO2 laser radiation at a wavelength of 10.6 m. Moreover, we exploited our computer-generated subwavelength gratings to demonstrate a polarization Talbot self-imaging, as well as nondiffracting periodically space-variant polarization beams, and a unique method for real-time polarization measurement. We also present novel optical phase elements based on the space-domain Pancharatnam-Berry phase. Unlike diffractive and refractive elements, the phase is not introduced through optical path differences, but results from the geometrical phase that accompanies space-variant polarization manipulation. We intoduce and experimentally demonstrate PancharatnamBerry phase optical elements (PBOEs) based on computer-generated subwavelength gratings such as polarization beamsplitters, optical switches and spiral phase.

Space-variant polarization state manipulation with computer-generated subwavelength metal stripe gratings

A novel approach to the design and analysis of space-variant polarization elements using computer-generated subwavelength metal stripe gratings is presented. We demonstrate that by locally controlling the direction and period of the grating any desired space-variant polarization state manipulation can be obtained. We illustrate our approach with two distinct types of manipulators: space-variant polarizers and space-variant polarization state transformations. The elements were formed on GaAs as well as ZnSe substrates and designed for laser radiation at 10.6 μ m. The results include full space-variant polarization calculations and measurements and show high-quality space-variant polarized beams with a polarization purity of over 99%.