College of Engineering 1996 Annual Report: Progress By Design Electrical and Computer Engineering
The helically symmetric stellarator is a doughnut-shaped magnetic confinement device under construction in the college. (71K JPG) Sketch of helically symmetric stellarator

Semiconductor-laser breakthroughs

Researchers at the college's Reed Center for Photonics have made technological breakthroughs that promise to radically reduce the costs and improve the reliability of fiber-optic networks while dramatically increasing the long-term reliability of diode lasers for use in medical therapy and pumping solid-state lasers. "We are able to get twice the coherent power previously achieved and potentially we will be able to get five times the coherent power of existing semiconductor lasers," says Dan Botez, Philip D. Reed professor. Botez's team has developed a new process for producing high-power, aluminum-free diode lasers in the 0.78 to 0.98 micron range. The technology promises to greatly improve signal boosters or "pumps" in telecommunications networks. Pumps are currently placed every 20 miles in fiber-optic cables. The new technology would allow spacing at 45-mile intervals, reducing the networks' cost significantly. Employing the Al-free InGaAs/InGaP/GaAs system at 0.98 microns, Botez's team achieved two world records for any type of semiconductor lasers: the highest CW output power from 100-micron aperture devices: 8.5 W; and the highest electrical-to-optical power conversion efficiency: 64 percent. The latter basically means that for each three electrons entering the device, two photons are emitted.

A new approach to confining plasma

HSX (Helically Symmetric Experiment) is a new concept in toroidal stellarators under construction at the HSX Plasma Laboratory under the direction of Professor J. Leon Shohet. A stellarator is a doughnut-shaped magnetic confinement device used to "bottle" hot plasma with the goal of achieving fusion. To improve the magnetic field for plasma confinement, the magnet coils have been designed with virtually no toroidal curvature. HSX will bridge the gap between asymmetric currentless stellarators and symmetric current-driven tokamaks. A tokamak is a plasma confinement device that requires a current flowing in the plasma in order to produce a magnetic "bottle." HSX research is supported by the U.S. Department of Energy.

Fine-tuned microwaves speed sintering

Microwave ovens are becoming increasingly important in industry for processing materials such as ceramics, glass and polymers more quickly and consistently than conventional gas-fired ovens. In fact, microwaves cause ceramic materials to join and solidify faster than traditional calculations say they should. Associate Professor John H. Booske and Materials Science and Engineering Professor Reid F. Cooper have isolated the mechanism that accelerates sintering. At the surface of a crystal, high-power microwaves (from 100 to 10,000 Watts) exert a peculiar (nonlinear) force that acts just like a mechanical pressure. This drives ionic diffusion, speeding the sintering process, Booske says. With this understanding, microwave ovens can be fine tuned for various applications such as processing ceramic engines.

Flexible AC transmission systems

Deregulation of electricity sales may require power lines to carry an increased power load. Professors Christopher L. DeMarco and Robert H. Lasseter along with members of the Power Systems Group --Professors Fernando L. Alvarado and Associate Professor Ian Dobson --are working to make this possible. Flexible Alternating Current Transmission Systems (FACTS) can rapidly switch in and out of electrical waveform to change the line's resistance to electricity. Unfortunately, these devices can add harmonic distortion to the electrical waveform causing malfunction in switching stations or generators.

Copyright 1996 University System Board of Regents

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Date last modified: Wednesday, 25-Sep-1996 12:00:00 CDT
Date created: 25-Sep-1996

1996 Annual Report Contents