Optical polarization

About: Optical polarization is a research topic. Over the lifetime, 13992 publications have been published within this topic receiving 244284 citations.

Circumstellar Grains and the Intrinsic Polarization of Starlight.

Abstract: Twenty-five long-period variable stars exhibiting intrinsic variable polarization have been monitored over the range 3.5-11 microns for several cycles. No conclusive evidence for gross changes in amount of circumstellar grains has been found. Thus circumstellar infrared emission is attributed to the total abundance of grains surrounding the star, which does not change by a large amount with time, while intrinsic polarization is attributed to more localized scattering and absorption effects. Spectrophotometry with resolution of about 0.015 over the 8-14 microns wavelength range of several stars with different chemical compositions indicates excess emission characteristic of 3 types of grains: (1) 'blackbody' grains, (2) silicate grains, and (3) silicon carbide grains.

Ultra-High Capacity WDM Transmission Using Spectrally-Efficient PDM 16-QAM Modulation and C- and Extended L-Band Wideband Optical Amplification

Abstract: This paper describes ultrahigh capacity transmission based on spectrally-efficient multi-level modulation and wideband optical amplification techniques. 21.4-Gbaud polarization-division multiplexed (PDM) 16-ary quadrature amplitude modulation (QAM) signals are generated by utilizing an optical synthesis technique, wavelength-multiplexed with 25-GHz spacing by optical pre-filtering, and received by an intradyne coherent receiver based on digital signal processing (DSP) with pilotless algorithms. These techniques realize a spectral efficiency (SE) of 6.4 b/s/Hz. Furthermore, a hybrid amplification technique that combines distributed Raman and dual-band erbium-doped amplifiers (EDFAs) realizes 10.8-THz signal bandwidth in C- and extended L-bands. By using these techniques, we successfully demonstrate 69.1 Tb/s transmission over 240 km of low loss pure silica core fibers.

A new short and low-loss passive polarization converter on InP

Abstract: We propose an improved polarization converter in InGaAsP-InP. It contains a series of waveguide sections with asymmetric cross-sections with angled facets. A 09-mm-long TE/TM-converter at a wavelength of 1.5 /spl mu/m is simulated. It contains 10 sections and has an excess loss of 0.25 dB. Both coupled mode theory and beam propagation method (BPM) simulations are included. >

Optical polarization and spectral variability in the m87 jet

Abstract: During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability was also seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST -1 shows a highly significant correlation between flux and polarization, with P increasing from approx 20% at minimum to > 40% at maximum, while the orientation of its electric vector stayed constant. HST-l's optical-UV spectrum is very hard (alpha(sub uv-0) approx. 0.5, F(sub v) varies as (v(exp -alpha)), and displays "hard lags" during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2alpha upper limits of 0.5 delta parsecs and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet PA, makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum ((alpha(sub uv-0) approx. 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

Xenon NMR Spectroscopy

Abstract: Xenon NMR spectroscopy has become an important and widely used tool for characterizing complex chemical systems and host phases. Issues central to new and existing uses of xenon NMR in materials research are emphasized, including xenon mass transport considerations, the sensitivity of xenon’s NMR parameters to local and macroscopic material structure and dynamics, and novel optical polarization techniques. After reviewing the foundations of 129Xe and 131Xe NMR spectroscopy methods, a number of applications are presented, particularly those focusing on new developments in the field.