Search results for "Linear polarization"
showing 10 items of 82 documents
Reversed polarized emission in highly strained a-plane GaN/AlN multiple quantum wells
2010
The polarization of the emission from a set of highly strained $a$-plane GaN/AlN multiple quantum wells of varying well widths has been studied. A single photoluminescence peak is observed that shifts to higher energies as the quantum well thickness decreases due to quantum confinement. The emitted light is linearly polarized. For the thinnest samples the preferential polarization direction is perpendicular to the wurtzite $c$ axis with a degree of polarization that decreases with increasing well width. However, for the thickest well the preferred polarization direction is parallel to the $c$ axis. Raman scattering, x-ray diffraction, and transmission electron microscopy studies have been p…
System for control of polarization state of light and generation of light with continuously rotating linear polarization
2019
We present a technique for generating light in an arbitrary polarization state. The technique is based on interference of two orthogonally polarized light beams, whose amplitudes and phases are controlled with a Mach-Zehnder inteferometer with acousto-optic modulators (AOMs) placed in each arm. We demonstrate that via control over amplitudes, phases, and frequencies of acoustic waves driving the AOMs, any polarization state can be synthesized. In particular, we demonstrate generation of linearly polarized light, whose polarization plane continuously rotates at a rate from 1 kHz to 1 MHz. Such light finds applications in science (e.g., investigations of Bloch-Siegert effect) and technology (…
Description of intermodulation generation of nonlinear responses beyond the validity of the power series expansion
2021
Weakly nonlinear responses are commonly described by a power series expansion. However, intermodulation distortion products that cannot be described by a power series have been observed in a variety of physical systems. As the power series description is only applicable within its radius of convergence, we choose an alternative approach based on Fourier coefficients to describe intermodulation levels beyond the convergence of the power series. The description over a wide power range allows us to make a decision about models and to determine previously inaccessible model parameters. We apply the approach to data obtained from the characterization of the nonlinear dielectric susceptibility of…
Laser-induced enhancement of tunneling in NHD2
2012
We apply and explore techniques aiming at enhancing the tunneling by laser fields, originally developed for a one-dimensional model, to a complete six-dimensional vibrational model of the inversion motion in NHD(2). The computational study is performed with the multi-configuration time-dependent Hartree method. Assuming an ideal three-dimensional alignment we obtain a driven tunneling time twenty times smaller than the natural one, in rather good agreement with an oversimplified three-state model. In the case of one-dimensional alignment, a linearly polarized field leads to a poor enhancement of the tunneling probability, after averaging over the rotation about the alignment axis, whereas a…
Evidence of oblate-prolate shape coexistence in the strongly-deformed nucleus 119Cs
2021
International audience; Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-rich A≈120 nuclei is reported for the first time. One of the four reported bands in 119Cs, built on a 11/2− state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupled πh11/2[505]11/2− configuration associated with oblate shape. Together with the decoupled πh11/2[541]3/2− band built on the 11/2− prolate state at 110 keV, for which a half-life of T1/2=55(5)μs has been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformed A≈120 nuclei, a phenomenon p…
Nonlinear mode coupling in a birefringent microstructured fiber tuned by externally applied hydrostatic pressure
2015
We studied the effect of power coupling between two linearly polarized modes, which occurs during nonlinear propagation in an externally tuned birefringent microstructured fiber. We investigated both experimentally and numerically the possibility of measuring hydrostatic pressure by tracking the nonlinear power coupling between the fiber polarization modes. We analyzed the impact of the fiber length exposed to pressure and the input polarization state on the coupling efficiency. We also revealed that the observation of nonlinear power coupling between the polarization modes is limited by linear coupling occurring in the leadthroughs to the pressure chamber. Moreover, we demonstrated that th…
High-pressure x-ray absorption study of GaTe including polarization
2000
The evolution of the local structure in GaTe under pressure is studied by x-ray absorption spectroscopy experiments at the Ga K-edge (10.368 keV) on oriented single crystals. Taking advantage of the linearly polarized character of synchrotron radiation, the pressure evolution of both the Ga-Te and the in-plane Ga-Ga bond lengths could be determined, in spite of the small amplitude of the latter. Our measurements show that both distances are much less compressible than what could be inferred from the bulk compressibility, which evidences a strong variation of Ga-Ga-Te and Te-Ga-Te angles under pressure. The Te-Te intralayer distance perpendicular to the layers is observed to increase with in…
High-Frequency Polarization Variability from Active Galactic Nuclei
2021
The linear polarization of non-thermal emission encodes information about the structure of the magnetic fields, either from the region where the emission is produced (i.e., the intrinsic polarization angle) and/or from the screens of magnetized plasma that may be located on its way towards Earth (i.e., the effect of Faraday rotation). In addition, the variability timescale of the polarized emission, or its Faraday rotation, can be used to estimate the size of the region where the emission (or the Faraday rotation) originates. The observation of polarized emission from active galactic nuclei (AGN) and, in particular, its time evolution, also provides information about the critical role that …
<title>Level-crossing spectroscopy of the 7, 9, and 10D states of Cs in an external electric field</title>
2007
We discuss experimental and theoretical studies of coherent excitation of magnetic sublevels in n D states of cesium that cross in an external electric field. Crossings of mF magnetic sublevels of hyperfine F levels with ΔmF = ±2 lead to resonances in the linearly polarized laser induced fluorescence, while crossings with ΔmF = ±1 lead to resonances in the circularly polarized laser induced fluorescence. These resonances can be exploited to observe alignment to orientation conversion. From the level crossing signals it is possible to measure atomic properties, such as the tensor polarizability α2 and the hyperfine constant A . Alignment to orientation conversion involves the deformation of …
Fe 2p photoemission magnetic dichroism with linearly polarized synchrotron radiation and with unpolarized A1 Kα radiation
1997
We report on the measurements and analysis of Fe 2p magnetic dichroism in the angular distribution of the photoelectrons from remanently magnetized Fe(100)surfaces with unpolarized, monochromatized A1 Kα X-rays of 1486 eV energy (MDAD)and with linearly polarized synchrotron radiation of energy 800 eV (LMDAD). The two experiments verify the atomic photoionization model of (L)MDAD including the dichroism effect between field-averaged experiments of different chirality.