Subpicosecond dynamics of the switching process in Y-Ba-Cu-O Josephson junctions

Roman Adam; Roman Sobolewski; Marian Darula

doi:10.1117/12.397842

6 September 2000 Subpicosecond dynamics of the switching process in Y-Ba-Cu-O Josephson junctions

Roman Adam, Roman Sobolewski, Marian Darula

Proceedings Volume 4058, Superconducting and Related Oxides: Physics and Nanoengineering IV; (2000) https://doi.org/10.1117/12.397842
Event: AeroSense 2000, 2000, Orlando, FL, United States

Abstract

We present comprehensive experimental and numerical studies of the subpicosecond switching dynamics of YBa₂Cu₃O_7-x (YBCO) grain-boundary Josephson junctions, excited by single-picosecond electrical pulses. The test structures were patterned in 100-nm- thick YBCO films grown by pulsed laser deposition on (100) MgO bicrystal substrates. Each sample consisted of a coplanar strip (CPS) transmission line, a microbridge acting as the electrical pulse generator, and a single Josephson junction positioned between the CPS lines about 100 micrometer away from the bridge. The junctions were characterized by the nonhysteretic current-voltage characteristics with the characteristic voltage approximately equal to 2.0 mV at 20 K (temperature of our experiments). A train of 100- fs-wide optical pulses from a Ti:sapphire laser photo-excited the microbridge and generated 2-ps-wide electrical pulses, which were then applied to switch the junction. In addition to the input pulse, the junction was dc-biased at +0.7 I_c, -0.7 I_c, +1.5 I_c, -1.5 I_c, and zero-I_c, where I_c is junction critical current. Time-resolved dynamics of the junction response was studied with the help of our cryogenic electro-optic sampling system, which can be regarded as a sampling oscilloscope featuring < 200-fs time resolution and < 150-(mu) V voltage sensitivity. We obtained 0.7-ps-wide single-flux-quantum (SFQ) pulses generated as a result of the junction switching process. The measurements were compared to numerical computations based on the equivalent circuit containing a resistively shunted Josephson junction, and we have found a satisfactory agreement between our simulations and experimental data. We believe our findings provide experimental confirmation of the potential of YBCO Josephson gattes as building blocks of ultrafast (sub-THz) digital electronics.

Citation Download Citation

Roman Adam, Roman Sobolewski, and Marian Darula "Subpicosecond dynamics of the switching process in Y-Ba-Cu-O Josephson junctions", Proc. SPIE 4058, Superconducting and Related Oxides: Physics and Nanoengineering IV, (6 September 2000); https://doi.org/10.1117/12.397842

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