Terahertz emission from YBa2Cu3O7-delta Josephson junctions excited by femtosecond laser

We examine both power and bias current dependence of terahertz (THz) emissi on properties from YBa2Cu3O7-delta (YBCO) Josephson junctions. The junction s coupled to bow-tie antennas are fabricated by Ar ion milling from YBCO th in films grown on MgO bicrystals. We observe the radiation at bias currents from 0 to 50 mA, laser powers from 0 to 250 mW. The radiation amplitude in creases with increasing laser power, and the frequency at which the radiati on has a maximum amplitude decreases with increasing laser power. These tre nds are observed regardless of junction voltage. The results suggest that t he voltage of the Josephson junction plays a less important role in the THz radiation excited by a femtosecond laser. (C) 2001 Elsevier Science B.V. A ll rights reserved.