Search results for "Circular polarization"
showing 10 items of 62 documents
Photoionization of Oriented Systems and Circular Dichroism
1996
Circular dichroism (CD) spectroscopy is a modification of normal absorption spectroscopy using circularly polarized light instead of unpolarized light for determining the difference in the absorption coefficients for right and left circularly polarized light, respectively, in optically active samples. Thus, there is nothing mysterious about CD spectroscopy. However, relative to most other spectroscopic techniques there seems to be a large psychological barrier in its application and at least physicists often regard CD, and optical activity in general, as a rather obscure technique without any useful application. There are some understandable reasons for this attitude, manifesting themselves…
Circular Dichroism in Photoemission from Nonmagnetic, Low- Z Solids: A Conspicuous Effect of the Photon Spin
1992
A new phenomenon has been observed in solid-state photoemission with circularly polarized light. Its outward appearance is similar to the circular dichroism in photoabsorption. For special observation geometries, large photoelectron intensity asymmetries arise upon reversal of the photon helicity. The effect is not based on spin-orbit interaction, as is demonstrated by the example of photoemission from graphite (Z = 6). Similar asymmetries are expected for all single-crystal solids thus opening up a new class of experiments providing new tests for photoemission theories. Detailed information on the dynamics of photoexcitation of a solid can be gained, as discussed in terms of a simple orbit…
Line of polarization attraction in highly birefringent optical fibers
2014
We investigate the phenomenon of polarization attraction in a highly birefringent fiber. This polarization process originates from the nonlinear interaction of two counter-propagating beams. We show that all polarization states of the forward (signal) beam are attracted toward a specific line of polarization states on the surface of the Poincare sphere, whose characteristics are determined by the polarization state of the injected backward (pump) beam. This phenomenon of polarization attraction takes place without any loss of energy for the signal beam. The stability of different stationary solutions is also discussed through intensive numerical simulations. On the basis of mathematical tec…
Circular Polarization of External Bremsstrahlung Produced by Beta Rays
1958
For energies smaller than 600 kev, the polarization was previously measured using forward scattering from magnetized iron, but a quantitative comparison was not performed. Computations were done for monoenergetic electrons falling on a thin absorber, whereas in all experiments the whole beta spectruan and thick absorbers were used. It is shown thnt even in this case a comparison with theory is possible as the diffusion of the electrons in the absorber has practically no influence on the polarization. Strong dependence of the circular polarization on the atomic number of the absorber is investigated. (W.D.M.)
Design of a Compact Dual Circular-Polarized Antenna for L-Band Satellite Applications
2020
In this paper, we propose the design of a dual circular-polarized antenna for L-band applications (1.1-1.6 GHz). The designed antenna has been developed by considering crossed-dipoles on top of which a circular patch has been placed to properly act on the mutual coupling between the dipoles. The dual circular polarization is achieved by feeding dipoles in quadrature. Moreover, to increase the antenna gain and polarization purity at high elevation angles, a fence of passive monopoles has been added. The proposed antenna can profitably used as primary feed of a low-frequency parabolic reflector.
Simulations of continuous-wave sodium laser guide stars with polarization modulation at Larmor frequency
2018
The return flux from a sodium laser guide star suffers, at large angles between the geomagnetic field and the laser beam, from the reduction in optical pumping due to spin-precession of sodium atoms. This detrimental effect can be mitigated by modulating the circular polarization of a continuous-wave laser beam in resonance with the Larmor frequency of sodium atoms in the mesosphere. We present an investigation based on numerical modeling to evaluate the brightness enhancement of a laser guide star with polarization modulation of a continuous-wave laser beam at different observatories.
On-Sky Tests of a High-Power Pulsed Laser for Sodium Laser Guide Star Adaptive Optics
2016
We present results of on-sky tests performed in the summer of 2013 to characterize the performance of a prototype high-power pulsed laser for adaptive optics. The laser operates at a pulse repetition rate (PRR) of 600–800[Formula: see text]Hz, with a 6% duty cycle. Its coupling efficiency was found to be, in the best test case (using 18[Formula: see text]W of transmitted power), [Formula: see text] photons s[Formula: see text] sr[Formula: see text] atom[Formula: see text] W[Formula: see text] m2 when circular polarization was employed and [Formula: see text] photons s[Formula: see text] sr[Formula: see text] atom[Formula: see text] W[Formula: see text] m2 with linear polarization. No impro…
Vector modes generation using efficient on-axis system
2020
Arbitrary polarized vector beam modes are efficiently generated. We use two flicker-free liquid-crystal on silicon (LCOS) spatial light modulators (SLM) in an on-axis common path architecture. Different superpositions of vector modes are obtained with high light efficiency.
Momentum partition between constituents of exotic atoms during laser-induced tunneling ionization
2015
The tunneling ionization of exotic atoms such as muonic hydrogen, muonium, and positronium in a strong laser field of circular polarization is investigated, taking into account the impact of the motion of the center of mass on the the tunneling ionization dynamics. The momentum partition between the ionization products is deduced. The effect of the center-of-mass motion for the momentum distribution of the ionization components is determined. The effect scales with the ratio of the electron (muon) to the atomic core masses and is nonnegligible for exotic atoms, while being insignificant for common atoms. It is shown that the electron (muon) momentum shift during the under-the-barrier motion…
On the observability of parity and time reversal violating interactions by trapped ion spectroscopy
1982
The feasibility to measure neutral weak current interactions by spectroscopy on trapped ions is investigated. The sensitivity of the proposed experiment is compared to the sensitivity of similar experiments using atomic gases or beams. It is shown that there is no advantage as far as that part of the interaction is concerned which is a vector in the nucleon current and an axial vector in the electron current. This is mainly due to the relatively low ion density. The circular polarization however depending upon the nuclear spin orientation appears to be proportional to the coherence time, which is three orders of magnitude longer than in ordinary atomic beam resonance experiments. It is poin…