This project involves the study of ultrafast phenomena in high temperature superconducting thin films. The Research Equipment Grant will enable construction of an ultrafast electro-optic sampling system to investigate the generation of nonequilibrium carriers by ultrashort laser pulses. Preliminary laboratory results by the principal investigator indicate the presence of such effects have been observed. Such effects should have important applications to ultrafast optical switching, and to ultrafast electrical pulse generation and propagation studies. These studies are also relevant to future opto- electronic integrated circuits applications. In the proposed experiments, high quality superconducting films as thin s 400 A are generated by the process of plasma-assisted laser deposition on various dielectric substrates, and patterned into transmission line structures. Since no post-annealing is necessary in this sample preparation technique, these lines are smooth with controllable grain sizes. Femtosecond laser pulses at various wavelengths are then used to measure the temporal response of these patterned films. Wavelengths from 0.4-4.4 um will be used. It is expected that the ultimate response time should be less than 1 ps for the new oxide superconductors. Such studies are also of fundamental interest to the understanding of nonequilibrium processes in high temperature 2- dimension superconductors. Other applications include ultrafast and wideband detection of radiation and ultrafast optical signal processing.
