Circular polarization

About: Circular polarization is a research topic. Over the lifetime, 15201 publications have been published within this topic receiving 234418 citations.

Inverse Faraday effect and propagation of circularly polarized intense laser beams in plasmas.

Abstract: The magnetic field generation through inverse Faraday effect and its effects on the propagation of a circularly polarized light wave are studied in a self-consistent way for relativistic intensities. The following results are presented. (i) The magnetic field is produced by two sources, the circular motion of single electrons which produces plasma magnetization, and the inhomogeneity of both the electron density and light intensity which produces nonzero currents in the azimuthal direction. The magnetic field is calculated for various profiles of electron density and light intensity. (ii) For the case of a plane wave in a homogeneous plasma, the cutoff frequency is calculated as a function of light intensity, which is different from that without consideration of magnetic field generation. An ultra-intense magnetic field as large as hundreds of MG is obtainable in an overdense plasma where the wave can propagate owing to the induced transparency. (iii) The evolution equations for a laser beam of finite width are derived. Due to magnetic field generation, the critical power for self-focusing of the laser beam is reduced by a factor of (1+${\mathrm{\ensuremath{\omega}}}_{\mathit{p}}^{2}$/${\mathrm{\ensuremath{\omega}}}^{2}$${)}^{\mathrm{\ensuremath{-}}1}$; the magnetic field tends to reduce the effect of the electron cavitation resulting from the transverse ponderomotive force. \textcopyright{} 1996 The American Physical Society.

Double-handed circular Bragg phenomena in polygonal helix thin films

Abstract: Oblique-incidence physical vapor deposition has been used to create optical thin films with a polygonal helix-shaped nanostructure. A series of titanium dioxide thin films are investigated, including triangle, square, pentagon, and star-shaped polygonal helices. Experimental optical measurements reveal a double-handed circular Bragg response: at one frequency band a polygonal helix reflects left-handed circularly polarized light, and at a second frequency band reflects right-handed circularly polarized light. The relative wavelength dependence of each reflection band is determined by the physical structure of the polygonal helix, a property that is set during the thin-film deposition process. Spectral-hole polarization filters, produced by adding twist and spacing layer defects to polygonal helix thin films, are also reported.

Ultrafast optical imaging of the spin Hall effect of light in semiconductors

Abstract: We experimentally demonstrate a general optical pump-probe technique to observe the spin Hall effect of light (SHEL) in an absorbing medium. In essence, a locally confined pump-induced modification of a material's absorptivity can effectively be used as an induced aperture allowing one to detect the transversely displaced circular polarization components of an incident beam through differential transmission techniques. We consider linear absorption mechanisms such as free-carrier absorption and Pauli blocking as well as nonlinear absorption processes such as two-photon absorption. For absorption mechanisms that do not depend on light polarization, the SHEL of the probe beam is obtained directly, while polarization-dependent properties give an effective SHEL displacement that depends on the action of the SHEL on both pump and probe beams. Using 150 fs pump, 820 nm pump and probe pulses we observe SHEL effects in silicon via free-carrier absorption. SHEL effects are also observed via Pauli blocking at 820 nm and two-photon absorption at 1550 nm in GaAs using $\ensuremath{\sim}150\text{ }\text{fs}$ pump and probe pulses.

Circularly polarised radiation from singly fed equilateral-triangular microstrip antenna

Abstract: The paper presents an equilateraltriangular microstrip antenna (MSA) that can produce circularly polarised waves with a single feed. Theoretically predicted results, such as the operating frequency and feed location with which good circularly polarised radiation can be obtained, are compared with experimentally obtained results. The calculations for the axial ratio and the radiation pattern are also compared with the measurements. For all of the results the agreement is found to be quite good, and it is confirmed that a singly fed equilateral-triangular MSA can produce two kinds of good circularly polarised waves at two different frequencies.

Design of Linear-to-Circular Polarization Transformers Made of Long Densely Packed Metallic Helices

Abstract: In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic waves in medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized wave may be transformed into a circularly polarized transmitted wave, and that the transmission efficiency of such polarization transformer may be as high as 95%. The theoretical results are supported by full wave simulations.