Glen M. McWright

A low leakage 10 000‐V silicon photoconductive switch

Under high bias voltage, the leakage current through a silicon photoconductive switch is mainly caused by carrier injection at the metallic contacts. A low leakage, high voltage silicon photoconductive switch is fabricated by the introduction of carrier trap centers between the silicon substrate and metallic contacts. We report 2.5‐mm gap photoconductive switches with leakage currents of less than 50 mA at a pulse bias of 10 kV for 600 ns, and an ‘‘on’’ resistance of less than 1.3 Ω, when illustrated by a 1‐ns, 1000‐μJ pulse of 1.05‐μm radiation.

Preliminary Radiation Hardness Testing Of LiNbO 3 :Ti Optical Directional Coupler Modulators Operating At 810 Nm

Integrated optics have the potential to replace conventional electronics in many instrumentation applications; in many cases the integrated-optics approach is the only one that will achieve the necessary bandwidth and information-density goals. Thus far, has been done to address the prompt hardness of these devices to intense ionizing-radiation fields. We present preliminary data on the response of optical directional coupler modulators (ODCMs) to radiation from a Febetron. The Febetron produces energetic electrons in the 300-700 keV range in tilde 3-ns FWHM pulses, with a maximum dose rate of tilde 1014 rad/s. The operation of the ODCM is monitored during and promptly after the Febetron pulse impinges the device. Long-term effets are also monitored. These data are analyzed with respect to the operation of such devipes in a harsh inonizing-radiation environment.

Gallium Arsenide Integrated Optical Devices For High-Speed Diagnostic Systems

We discuss the design, fabrication, and evaluation of waveguide electro-optic modulators in gallium arsenide for application to high-speed diagnostic systems. We focus specifically on high bandwidth, single event analog modulation, and radiation susceptibility of these devices.

Simplified theory of variable impedance stripline under pulse excitation

This paper describes a simple method to predict the transient response of variable impedance stripline to pulse excitation. The technique uses a finite‐difference‐based quasi‐static impedance formulation to calculate the reflection coefficient at each point along the direction of pulse propagation. Excellent correlation between predictions and results obtained via time‐domain reflectometry was noted.

Integrated optical devices for photonics instrumentation systems

We discuss the design, fabrication, and evaluation of high speed integrated optical devices for application to photonics insirumentation systems. Specifically, we have demonstrated integrated optical devices with bandwidths in excess of 25GHz and implemented these devices in single-shot, streak camera based recording schemes.

All-optical modulation in gallium arsenide integrated optical waveguides

We have investigated all-optical modulators in gallium arsenide integrated optical waveguides; these modulators use electron-hole pair generation to alter the propagation characteristics of a guided light beam.

Photonic Applications Of Thin Film Gaas Grown On Silicon And Insulating Substrates By Molecular Beam Epitaxy

Thin film GaAs layers grown by Molecular Beam Epitaxy (MBE) on silicon, semi-insulating GaAs, and insulating substrates have been investigated for application to optoelectronic circuit technology. Photoconductivity measurements were conducted to characterize the electronic transport properties of the epitaxial layers in terms of carrier recombination lifetime and effective drift mobility. By varying the epitaxial growth parameters, it is possible to obtain various levels of material quality which are suitable for various components of optoelectronic integrated circuits. Results from photodetectors fabricated from GaAs grown on various layers will be presented. The fabrication of ridge waveguides from GaAs grown on silicon dioxide will also be described. Finally, a procedure for growing high quality GaAs for active devices in situ with layers for picosecond photoconductors will be discussed.

Radiation Effects On Gallium Arsenide Integrated Optical Devices

We discuss gallium arsenide integrated optical devices for high speed diagnostic systems. Specifically, we focus on the effect of radiation exposure on the performance characteristics of these devices.