I. Iguchi et al., Emitted spectra of electromagnetic waves from a tunnel-injected nonequilibrium high-T-c YBa2Cu3O7-y superconductor, PHYS REV B, 62(9), 2000, pp. 5370-5373
We report the measurements on the emitted spectra of terahertz electromagne
tic waves from a tunnel-injected nonequilibrium high-T-c YBa2Cu3O7-y (YBCO)
superconductor using a high-T-c YBCO Josephson spectroscopic detector fabr
icated on the same chip. The observed spectrum appeared as a single broad-p
eaked structure with peak frequency typically at about 5 THz at low tempera
ture. The dependencies of peak frequency and line shape on temperature, c-a
xis current, and oxygen deficiency are investigated. The results are consis
tently interpreted in terms of Josephson plasma emission characteristic of
oxide sugerconductors with optimal doping.