Search results for "Guide"
showing 10 items of 1478 documents
Acoustic phonons for coherent photon control in semiconductor structures
2007
We present a novel concept for acousto-optical modulation in waveguide (WG) structures using coherent phonons in the form of surface acoustic waves (SAWs). Here, a SAW impinging perpendicular to a waveguide structure induces a change in phase of the light propagating through it, which is translated into a transmission intensity modulation by using the WG as an arm of a Mach-Zehnder interferometer (MZI). We show that the modulation becomes strongly enhanced if the SAW induces phase changes of opposite sign in the MZI arms. Very compact modulators with an interaction length between the optical and acoustic waves of approx. 15 µm have been fabricated using focusing acoustic transducers to gene…
Interacting Solitons in a High Index Glass
2010
We investigate the interaction of two coherent 2D+1 solitary beams in a high index glass.
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…
Efficient Pole Expansion of the Generalized Impedance Matrix Representation for Planar Waveguide Junctions
2006
This paper proposes a novel pole expansion of the generalized impedance matrix representation for planar waveguide junctions. Proceeding in this way, we have obtained a very efficient algorithm for the accurate wide-band modelling of such junctions, since the most expensive computations are performed outside the frequency loop. For verification purposes, several practical examples are shown in order to prove the numerical efficiency and accuracy provided by this new technique.
Asymptotic and Numerical Studies of Resonant Tunneling in 2D-Waveguides for Electrons of Small Energy
2021
Chapter 5 is devoted to asymptotic studies of electron resonant tunneling in a two-dimensional waveguide with two narrows. The narrow diameter plays the role of a small parameter. The asymptotics of basic characteristics of resonant tunneling are presented for electrons with energy between the first and the second thresholds. Moreover, the asymptotics results are compared with numerical ones obtained by approximate calculation of the scattering matrix.
Multipactor Analysis in Circular Waveguides
2009
[EN] This paper mainly focuses on demonstrating that a multipactor discharge can occur within a circular waveguide operating under the fundamental TE11 circular mode. Circular waveguides are widely used in the fabrication of many passive components, in order to implement resonant cavities as well as irises to connect adjacent guides for both application domains, particle accelerators and satellite subsystems applications. Thus, we present the first study of the multipactor effect in a circular waveguide, demonstrating its existence and providing a susceptibility chart for such a structure, which will be of great interest for the better understanding of multipactor physical phenomena.
Large data scattering for NLKG on waveguide ℝd × 𝕋
2020
We consider the pure-power defocusing nonlinear Klein–Gordon equation, in the [Formula: see text]-subcritical case, posed on the product space [Formula: see text], where [Formula: see text] is the one-dimensional flat torus. In this framework, we prove that scattering holds for any initial data belonging to the energy space [Formula: see text] for [Formula: see text]. The strategy consists in proving a suitable profile decomposition theorem on the whole manifold to pursue a concentration-compactness and rigidity method along with the proofs of (global in time) Strichartz estimates.
SU-GG-T-227: Dynamic IMRT Split Beam Technique Verification Using EPID Based Dosimetry
2010
Purpose: On dynamic IMRT plans with Millenium 80 (Varian) fields wider of 15 cm must be splitted. Since the EPIDdosimetry software does not allow to sum splitted subfluences in the same dosimetric portal image they have to be measured separately and compared independently with the subfluences previously calculated by the TPS Eclipse. The purpose of our work is the development of a tool to: 1) analyze the correct match between the two abutted ports for splitted fields. 2) study the effect of gravity and analyze repercussions of possible misalignments and 3) illustrate that the gamma evaluation should be made with the global summed fluence per field instead of with the individual subfluences.…
Improved ion guide for heavy-ion fusion-evaporation reactions
1998
The ion guide for heavy-ion-induced reactions developed originally for the SARA facility in Grenoble has been implemented at the Jyvaskyla IGISOL facility. For the Cd-116(Ar-40, 6n)Dy-150 reaction an efficiency of 0.5% relative to the number of reaction products entering the stopping chamber was obtained. This is 3.5 times higher than previously obtained at SARA and corresponds to a yield of about 100 ions/(p mu C mb). Mass-separated yields for the Ar-36 + Mo-92 and Ar-36 + Mo-94 reactions were measured. (C) 1998 Elsevier Science B.V. All rights reserved.