Search results for " Polarization"
showing 10 items of 668 documents
Modeling of photonic crystal fibers from the scalar wave equation with a purely transverse linearly polarized vector potential
2011
In this work, we propose a new technique for modeling light propagation in photonic crystal fibers where the electric field is evaluated from a purely transverse linearly polarized vector potential. The vector potential in a nonuniform dielectric obeys a wave equation coupled to the scalar potential, but it can be reduced to a scalar wave equation when the coupling term is ignored to the lowest order approximation. We show that this method gives reliable results for photonic crystal fibers when the scalar analysis is improved by a perturbational correction.
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…
Efficient on-axis SLM engineering of optical vector modes
2020
Abstract This work presents a method for the efficient experimental generation of arbitrary polarized vector beam modes. The optical system employs two liquid-crystal on silicon (LCOS) spatial light modulators (SLM) in a common path architecture, avoiding the use of beam-splitters. Each SLM displays a different phase-only mask, each one encoding a different pattern onto two orthogonal linear polarization components of the input beam. These phase-only masks are designed using a recently proposed random technique to encode complex amplitude values. This encoding technique reconstructs the complex function on-axis, thus avoiding incorporating carrier phases. By addressing such properly designe…
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.
Accurate calculation of the transverse anisotropy of a magnetic domain wall in perpendicularly magnetized multilayers
2015
Bloch domain walls are the most common type of transition between two out-of-plane magnetized domains (one magnetized upwards, one downwards) in films with perpendicular magnetic anisotropy. The rotation of the spins of such domain walls in the plane of the film requires energy, which is described by an effective anisotropy, the so-called transverse or hard axis anisotropy ${K}_{\ensuremath{\perp}}$. This anisotropy and the related D\"oring mass density of the domain wall are key parameters of the one-dimensional model to describe the motion of magnetic domain walls. In particular, the critical field strength or current density where oscillatory domain wall motion sets in (Walker breakdown)…
Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets
2015
Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spinconserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ∼∇ 2 [m × (u · ∇)m] + ξ ∇ 2 [(u · ∇)m], where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dyna…
Electrically Controlled Pumping of Spin Currents in Topological Insulators
2011
Pure spin currents are shown to be generated by an electrically controlled quantum pump applied at the edges of a topological insulator. The electric rather than the more conventional magnetic control offers several advantages and avoids, in particular, the necessity of delicate control of magnetization dynamics over tiny regions. The pump is implemented by pinching the sample at two quantum point contacts and phase modulating two external gate voltages between them. The spin current is generated for the full range of parameters. On the other hand, pumping via amplitude modulation of the inter-boundary couplings generates both charge and spin currents, with a pure charge current appearing o…
Persistent spin and charge currents and magnification effects in open ring conductors subject toRashba coupling
2007
We analyze the effect of Rashba spin-orbit coupling and of a local tunnel barrier on the persistent spin and charge currents in a one-dimensional conducting Aharonov-Bohm (AB) ring symmetrically coupled to two leads. First, as an important consequence of the spin-splitting, it is found that a persistent spin current can be induced which is not simply proportional to the charge current. Second, a magnification effect of the persistent spin current is shown when one tunes the Fermi energy near the Fano-type antiresonances of the total transmission coefficient governed by the tunnel barrier strength. As an unambiguous signature of spin-orbit coupling we also show the possibility to produce a p…
A paradigm of fullerene
2009
We study the dynamics of an electron constrained over the surface of a rigid sphere, with geometrical parameters similar to those of the C60 fullerene, embedded in a low intensity linearly polarized laser field. The model is shown to emit odd harmonics of the laser even at very low field intensity. For more intense laser fields, the spectrum presents odd harmonics and hyper-Raman lines shaped in a broad plateau. The spectrum of the model is compared to that theoretically obtained by other authors for more realistic models of C60. It is concluded that the model can be used as a paradigm for mesoscopic molecules in the fullerene family, particularly in practical applications where it is conve…
Light polarization measurements in tests of macrorealism
2018
According to the world view of macrorealism, the properties of a given system exist prior to and independent of measurement, which is incompatible with quantum mechanics. Leggett and Garg put forward a practical criterion capable of identifying violations of macrorealism, and so far experiments performed on microscopic and mesoscopic systems have always ruled out in favor of quantum mechanics. However, a macrorealist can always assign the cause of such violations to the perturbation that measurements effect on such small systems, and hence a definitive test would require using non-invasive measurements, preferably on macroscopic objects, where such measurements seem more plausible. However,…