Circular polarization

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

Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology

Abstract: Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.

Linear and circular-polarization conversion in X-band using anisotropic metasurface.

Abstract: An ultrathin single-layer metasurface manifesting both linear cross-polarization conversion (CPC) and linear-to-circular polarization (LP-to-CP) conversion in X-band is presented in this research. The designed metasurface acts as a multifunctional metasurface achieving CPC over a fractional bandwidth of 31.6% (8–11 GHz) with more than 95% efficiency while linear-to-circular polarization conversion is realized over two frequency bands from 7.5–7.7 GHz and 11.5–11.9 GHz. Moreover, the overall optimized structure of the unit cell results in a stable polarization transformation against changes in the incidence angle up to 45° both for transverse-electric (TE) and transverse-magnetic (TM) polarizations. The proposed metasurface with simple structure, compact size, angular stability and multifunctional capability qualifies for many applications in communication and polarization manipulating devices.

Polarization of Astronomical Maser Radiation. III. Arbitrary Zeeman Splitting and Anisotropic Pumping

Abstract: General solutions of the maser polarization problem are presented for arbitrary absorption coefficients. The results are used to calculate polarization for masers permeated by magnetic fields with arbitrary values of \xB, the ratio of Zeeman splitting to Doppler linewidth, and for anisotropic pumping. The $\xb \to 0$ limit of the magnetic solution reproduces the linear polarization derived in previous studies, which were always conducted at this unphysical limit. While terms of higher order in \xb\ have a negligible effect on the magnitude of $q$, they produce some major new results. In particular, the linear polarization is accompanied by circular polarization, proportional to \xb. Because \xb\ is proportional to the transition wavelength, the circular polarization of SiO masers should decrease with rotation quantum number, as observed. In the absence of theory for $\xb < 1$, previous estimates of magnetic fields from detected maser circular polarization had to rely on conjectures in this case and generally need to be revised downward. The fields in SiO masers are \about\ 2--10 G and were overestimated by a factor of 8. The OH maser regions around supergiants have fields of \about\ 0.1--0.5 mG, which were overestimated by factors of 10--100. The fields were properly estimated for OH/IR masers ($\la$ 0.1 mG) and \H2O masers in star-forming regions (\about\ 15--50 mG). Spurious solutions that required stability analysis for their removal in all previous studies are never reproduced here; in particular, there are no stationary physical solutions for propagation at $\sin^2\theta < \third$, where $\theta$ is the angle from the direction of the magnetic field, so such radiation is unpolarized. These spurious solutions can be identified as the \xb\ = 0 limits of non-physical solutions and they never arise at finite

Above-Threshold Ionization by an Elliptically Polarized Field: Quantum Tunneling Interferences and Classical Dodging

Abstract: Measurements of above-threshold ionization electron spectra in an elliptically polarized field as a function of the ellipticity are presented. In the rescattering regime, electron yields quickly drop with increasing ellipticity. The yields of lower-energy electrons rise again when circular polarization is approached. A classical explanation for these effects is provided. Additional local maxima in the yields of lower-energy electrons can be interpreted as being due to interferences of electron trajectories that tunnel out at different times within one cycle of the field.

Chiral-Selective Plasmonic Metasurface Absorbers Operating at Visible Frequencies

Abstract: We demonstrate theoretically and experimentally a chiral-selective plasmonic absorber by utilizing n-shaped-resonators in the visible frequencies. Our metasurface design enables chiral-selective absorption bands, in which absorption peaks for left-handed circularly polarized and right-handed circularly polarized occur at different resonance wavelengths resulting in significant circular dichroism (CD). Both simulated and measured absorption spectra exhibit maximum absorptions exceeding 80% associated with a CD value of ~0.5. Such a chiral plasmonic metasurface absorber with high performance could find applications in optical filters, non-linear optics, thermal emitters, and hot-electron collection devices.