Electromagnetics and Photonics Commons^™

Self-Enhancement Of Dynamic Gratings In Photogalvanic Crystals, Nickolai Kukhtarev, Sergei F. Lyuksyutov, Preben Buchhave, Tatiana Kukhtareva, K. Sayano, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

We have developed a compact closed-form solution of the band transport model for high-contrast gratings in photogalvanic crystals. Our solution predicts the effect of the photoconductivity and the electric field grating enhancement due to the photogalvanic effect. We predict a pronounced dependence of the steady-state photogalvanic current on the contrast of the interference pattern and an increase of holographic storage time due to the enhancement of the photoconductivity grating contrast. In the high contrast limit and a large photogalvanic effect the refractive index grating will be shifted from the position of the intensity modulation pattern, contrary to the usually adopted …

Experimental Investigations Of Wavelength And Angular Errors In Holographic Gratings With Non-Bragg-Matched Read Beams, Monish Ranjan Chatterjee, Vivek Ray

Electrical and Computer Engineering Faculty Publications

Perfect Bragg matching is generally desirable for accurate optical interconnections with holographic gratings. In reality, however, gratings may be illuminated by READ beams with non-Bragg-matched angles, or wavelengths, or both. In such cases, the scattered beams are generally misdirected, and may suffer loss of efficiency and possibly more serious errors such as crosstalk noise or missed connections. A conventional wave-vector triad method of analyzing the scattered beam errors leads readily to near-Bragg estimates of the output angular misalignment. However, the READ wave-vector triads appear to indicate a possible wavelength shift in the output beam even with a Bragg-matched READ wavelength, …

Field Emission And Breakdown Processes In Vacuum Gaps With Sio(X)-Coated Cathodes, Raymond Jack Allen Iii

Electrical & Computer Engineering Theses & Dissertations

Field emission of electrons is the major cause of electrical breakdown in high voltage systems in vacuum. The highest hold-off electric field of the carefully polished and cleaned stainless steel cathodes was increased to 70MV/m. Thin silicon monoxide, SiO_x, cathode coatings reduced field emission and increased the hold-off field further. Coating the stainless steel cathodes with 2μ SiO_x reduced the field emission current by at least two orders of magnitude at field of 50MV/m and increased the breakdown field to 140MV/m, doubling the breakdown voltage.

The increase in hold-off voltage with SiO_x coatings is discussed in …

Electromagnetic Scattering From Coated Strips Utilizing The Adaptive Multiscale Moment Method, C. Shu, T. K. Sarkar

Electrical Engineering and Computer Science - All Scholarship

The aim of this paper is to consider the problem of electromagnetic scattering from perfectly conducting strips coated with thin dielectric material by use of the adaptive multiscale moment method (AMMM). In the next section, the basic formulation is presented for analysis of scattering from coated conducting strips on the basis of a coupled system of electric- and magnetic-field integral equations. Section 3 outlines the computational methodology of the multiscale basis by use of the moment method. Section 4 presents AMMM to solve the coupled EM integral equations. Section 5 presents a variety of numerical examples for different coating strips …

Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka

Electrical and Computer Engineering Faculty Publications

In many practical situations, it is important to determine and measure the attitude of a particular vehicle, such as a ship, an airplane, a piece of mechanical equipment such as a, crane lifter, or a spacecraft. For this reason, many attitude sensors have been developed with advanced computer and semiconductor technologies. This section first introduces the various attitude sensors with an explanation of their operating principles and then presents several methodologies for attitude measurement and determination, including ships and crane lifters, aircraft, and spacecraft applications.

Modeling Electromagnetic Disturbances In Closed-Loop Computer Controlled Flight Systems, W. Steven Gray, Oscar R. Gonzalez

Electrical & Computer Engineering Faculty Publications

High intensity electromagnetic radiation has been demonstrated to be a source of computer upsets in commercially available digital flight control systems. In this paper we introduce an electromagnetic disturbance model which can be used for stability analysis and augmentation of any such digitally implemented control law. The model is composed of a Markovian exosystem supplying radiation events to a discrete-time jump linear system which models how the radiation interferes with the nominal operation of the closed-loop system. We discuss how this model can be used to characterize stability and how it can be parametrized and validated in an experimental setting.