Picosecond response of optically driven Y-Ba-Cu-O microbridge and Josephson-junction integrated structures

• Published in: IEEE transactions on applied superconductivity Vol. 9; no. 2; pp. 4091 - 4094
• Main Authors: Adam, R., Currie, M., Sobolewski, R., Harnack, O., Darula, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-06-1999; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; BICRYSTALS; Circuit testing; Coplanar transmission lines; COPPER OXIDE; ELECTRIC CIRCUITS; Electrical junctions; Electronics; Exact sciences and technology; Excitation; Josephson junctions; Laser ablation; Laser excitation; MICRO ORGANISMS; Microorganisms; Optical films; Optical pulse generation; Optical pulses; Optoelectronic devices; SAMPLING; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; SUPERCONDUCTORS; Transmission lines; Ultrafast optics; YBCO superconductors; Yttrium barium copper oxide; YTTRIUM OXIDE; Electric pulse; Picosecond; Microbridge; Experimental result; Transmission line; Josephson junction; Integrated circuit; Optoelectronic device; Coplanar line; Optical pulse; Bicrystal; Grain boundary
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/77.783925

We report our studies on single-picosecond electrical pulse excitation and detection in YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) transmission lines containing microbridges and grain-boundary Josephson junctions. The structures were patterned in YBCO films grown by laser ablation on MgO bicrystals and consisted of 20-/spl mu/m-wide coplanar lines, separated by a 20-/spl mu/m-wide gap. Each transmission line contained a 5-/spl mu/m-wide and 10-/spl mu/m-long microbridge and a 5-/spl mu/m-wide grain-boundary weak link, and was overlaid with 50 nm of Au to improve its high frequency properties. Using a Ti:sapphire laser, we excited the microbridge with 100-fs-wide 400-nm-wavelength optical pulses and studied response of our test structures, utilizing a cryogenic electro-optic sampling system. We directly observed 2.1-ps-wide pulses generated by YBCO microbridges, as well as the single-picosecond Josephson junction response. The junction response depended directly on the current bias and its polarity with respect to the excitation electrical pulse, and exhibited single-flux-quantum-like characteristics. Our test structures can be regarded as examples of all-YBCO ultrafast optoelectronic circuits.