Ultrafast Optical Switching in High Temperature Superconducting Films
Hoi Kwok Principal Investigator
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This project involves the study of ultrafast processes in high temperature superconductors. Femtosecond duration laser pulses will be used to study the response times of simple high Tc superconducting electronic devices. The goal is to investigate the possibility of using these high Tc materials in active ultrafast electronic devices such as switches and transistors at 77K. Preliminary results have shown that the response times of Y-Ba-Cu-O superconductors can be as fast as 1 ps. In this research program, high quality in-situ superconducting thin films will be deposited by pulsed excimer lasers onto various substrates and patterned into various calculated geometries. Microstriplines will be used predominantly, although other structures will also be examined. Additionally, the use of hibrid devices involving both superconducting and semiconducting films will be investigated. The relaxation times after laser excitation will be measured by optical as well as electrical techniques as a function of material parameters such as doping and crystallinity of the films. The use of granular films and weak link junctions to increase the speed of these devices will also be studied. Besides applications to ultrafast electronics, this project will also contribute to the fundamental understanding of nonequilibrium phenomena in high Tc superconductors.