Title :
Millimeter and submillimeter wave responses of YBa/sub 2/Cu/sub 3/O/sub 7/ step-edge Josephson junctions
Author :
Shimakage, H. ; Uzawa, Y. ; Wang, Z. ; Kawakami, A. ; Chujo, W. ; Komiyama, B.
Author_Institution :
Commun. Res. Lab., Kansai Adv. Res. Center, Kobe, Japan
fDate :
6/1/1995 12:00:00 AM
Abstract :
We have fabricated YBCO step-edge Josephson junctions and measured the responses to millimeter and submillimeter irradiation. In the substrate milling process for the purpose of fabricating the step, the step angle was controlled using a Nb metal mask. At a step angle of 20 degrees, we obtained Josephson junctions, the characteristics of which are consistent with the RSJ model. We estimated the capacitance to be 4.4 fF using the RSJ model, but such a value for an 8 /spl mu/m wide and 300 nm thick junction seems too small. When the junctions were irradiated by 300 GHz radiation, Shapiro steps up to the 4th were observed. The junctions were used as mixers in the 100 GHz band, and as harmonic mixers in the 100 GHz LO and 700 GHz RF bands. Beat signals were observed in both cases. We also estimated the quasi-optical conversion losses of the step-edge junctions as mixers.<>
Keywords :
Josephson effect; barium compounds; high-temperature superconductors; millimetre wave mixers; submillimetre wave mixers; superconducting device testing; superconducting junction devices; superconducting microwave devices; yttrium compounds; 100 GHz; 300 GHz; 300 nm; 4.4 fF; 700 GHz; 8 mum; MgO; Nb; Nb metal mask; RSJ model; Shapiro steps; YBa/sub 2/Cu/sub 3/O/sub 7/; YBa/sub 2/Cu/sub 3/O/sub 7/ step-edge Josephson junctions; beat signals; harmonic mixers; millimeter irradiation; millimeter wave response; mixers; quasi-optical conversion losses; step angle control; submillimeter irradiation; submillimeter wave response; substrate milling process; Bridge circuits; Ion beams; Josephson junctions; Niobium; Resists; Sputter etching; Sputtering; Substrates; Superconductivity; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
