OPTICAL DIAGNOSTICS FOR FABRICATION OF YBCO THIN-FILM DC-SQUIDS

Optical reflectance spectra of thin YBCO films on SrTiO3 bicrystals we re measured in a photon energy range of 1-3 eV at room temperature. Ra man spectra measurements in range 200-700 cm(-1) were performed. The b est samples were shown to have high reflectance anisotropy and well-de fined peak nu(1)=500+/-1 cm(-1) in Raman spectra. YBCO thin films on b icrystal substrate that successfully passed optical control were used for Josephson junctions and dc SQUIDs fabrication. The fabricated dc S QUIDs operated at 77.3 K in the flux locked loop mode had a typical wh ite noise (1-2)x10(-5) Phi(0)/Hz(1/2) at frequencies higher than 200-5 00 Hz. The best obtained magnetic field resolution was 650 fT/Hz(1/2) at frequencies f > 200 Hz.