A program of study of planar dielectric grating couplers was undertaken. The study focused on the problems associated with using dielectric grating couplers to achieve high efficiency beam coupling to planar waveguide

Abstract. We demonstrate how the Rashba spin-orbit coupling in semiconductor heterostructures can produce and control a spin-polarized current without ferromagnetic leads. Key idea is to use spin-double refraction of an electronic beam with a nonzero incidence angle. A region where the spin-orbit coupling is present separates the source and the drain without spin-orbit coupling. We show how the...

In this paper, a generalized particle system (GPS) method, a general method to describe multiple strong form representation based particle methods is described. Gradient, divergence, and Laplacian operators used in various strong form based particle method such as moving particle semi-implicit (MPS) method, smooth particle hydrodynamics (SPH), and peridynamics, can be described by the GPS metho...

In the design of modern accelerators, an accurate estimate of coupling impedance is very important. The sources which give rise to coupling impedance are the geometric discontinuities in the accelerator beam pipe. In various discontinuities such as RF cavities, bellows, and collimators, the coupling impedance of the holes has not been well understood. Although coupling impedance can be obtained...

For many industrial and scientific laser applications, such as materials processing, fiber coupling, beam collimation, and beam focusing, it is necessary to have a good laser beam quality. In general, propagating laser beams deviate from an ideal Gaussian intensity distribution. The degree of deviation can be conveniently quantified by a quality factor M (called the “M-squared” factor or the “t...

Open boundary conditions. Since the source current, Eq. 1, extends from z = −∞ to +∞ whereas our computational domain is finite, one has to apply suitable boundary conditions (see also [2]). Consider some accelerator component, residing in a vacuum cavity with attached beam pipe of smaller cross section than the cavity. Generally, the transitions from the pipe to the module have to be included ...

In this paper airflow, nano-and micro-particle motions in an aerodynamic particle beam focusing system consisting of several lenses, a nozzle and the downstream chamber, was studied. A three-dimensional numerical simulation for the system was presented and the compressible airflow and thermal conditions in the aerodynamic lens system were evaluated. Dilute particle concentration was assumed so ...

In this paper, the nonlinear vibration behavior of a rotor with asymmetric shaft considering misalignment is studied. The system consists of a rectangular shaft and a disk which is connected to a motor through a flexible coupling. In order to consider higher order deformations, nonlinear Bernoulli beam is used for modeling the shaft. Gibbons’ equations are utilized to apply misaligned coupling ...

This paper presents the design optimization of the coupling beam of wine glass (WG) mode micromechanical disk filters using the simulated annealing algorithm. The filter under consideration consists of two identical wine-glass mode disk resonators, mechanically coupled by a flexural mode beam. Such coupled two-resonator system exhibits two mechanical resonance modes with closely spaced frequenc...