Circular polarization

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

Polarization time and length for random optical beams

Abstract: We investigate the dynamics of the instantaneous polarization state of stationary, partially polarized random electromagnetic beamlike fields. An intensity-normalized correlation function of the instantaneous Poincare vector is introduced for the characterization of the time evolution of the polarization state. This polarization correlation function enables us to define a polarization time and a polarization length over which the polarization state remains substantially unchanged. In the case of Gaussian statistics, the polarization correlation function is shown to assume a simple form in terms of the parameters employed to characterize partial coherence and partial polarization of electromagnetic fields. The formalism is demonstrated for a partially polarized, temporally Gaussian-correlated beam, and black-body radiation. The results are expected to find a range of applications in investigations of phenomena where polarization fluctuations of light play an important role.

Raman optical activity instrument for biochemical studies

Abstract: A simple and fully computer-controlled backscattering incident circular polarization Raman optical activity (ICP ROA) instrument suitable for chioptic studies of biologically significant molecules in aqueous solution is described. It consists of a fast single-stage monochromator equipped with a holographic edge filter, a highly efficient holographic difiaction grating and a thinned back illuminated thermoelectrically cooled charge-coupled device detector as the key spectral elements. A longitudinal electro-optic modulator is employed to switch between orthogonal circular polarization states in the incident laser radiation within a backscattering geometry. A thick Lyot depolarizer is used for the depolarization of the backscattered Raman radiation. High-quality backscattering ICP ROA spectra of (1S)-( − )-trans-pinane, (1R)-( + )-trans-pinane, L-alanine, L-alanyl-L-alanine, lysozyme, D-glucose, α-D-cyclodextrin and 2′-deoxycytidine are presented as typical examples of the excellent performance characteristics.

Terahertz Vortex Beam as a Spectroscopic Probe of Magnetic Excitations

Abstract: Circularly polarized light with spin angular momentum is one of the most valuable probes of magnetism. We demonstrate that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetism exhibiting dichroisms in a magnetized medium. Resonant optical absorption in a ferrimagnetic crystal depends strongly on both the handedness of the vortex and the direction of the beam propagation with respect to the sample magnetization. This effect exceeds the conventional dichroism for circularly polarized light. Our results demonstrate the high potential of the vortex beams with OAM as a new spectroscopic probe of magnetism in matter.

Linear polarized fluctuations in the cosmic microwave background

Abstract: It has been recognized since the early work of Silk1 and Sachs and Wolfe2 that inhomogeneities in density, velocity fields or gravitational potential can produce small amplitude fluctuations in the intensity of the cosmic microwave background on small angular scales. Searches3 for such intensity fluctuations on scales of arc seconds to degrees have now reached sensitivities of 10−4 in ΔT/T or better (where T is the temperature of the background). It is less often noted that density inhomogeneities can introduce small-scale fluctuations in linear polarization into the microwave background. Work by Bond and Efstathiou4 in the context of cold dark matter models for the origin of galaxies, for instance, suggests that fluctuations in polarization will be present on characteristically smaller angular scales than total intensity fluctuations, and will be ∼1/10 their amplitude. Lubin et al.5 have shown that the large-scale linear polarization is ≲0.2 mK, or ≲7 x 10−5 in ΔT/T. We report here limits on the linear (and circular) polarization of the cosmic microwave background on small angular scales,18″≤ Θ≤160″.

Geometric metasurface enabling polarization independent beam splitting.

Abstract: A polarization independent holographic beam splitter that generates equal-intensity beams based on geometric metasurface is demonstrated. Although conventional geometric metasurfaces have the advantages of working over a broad frequency range and having intuitive design principles, geometric metasurfaces have the limitation that they only work for circular polarization. In this work, Fourier holography is used to overcome this limitation. A perfect overlap resulting from the origin-symmetry of the encoded image enables polarization independent operation of geometric metasurfaces. The designed metasurface beam splitter is experimentally demonstrated by using hydrogenated amorphous silicon, and the device performs consistent beam splitting regardless of incident polarizations as well as wavelengths. Our device can be applied to generate equal-intensity beams for entangled photon light sources in quantum optics, and the design approach provides a way to develop ultra-thin broadband polarization independent components for modern optics.