Study on Sub-THz Signal Input for Superconducting Electronic Devices

Yasushi DODA
Ryuhei KINJO
Toshihiko KIWA
Masayoshi TONOUCHI

IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.3    pp.588-594
Publication Date: 2007/03/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.3.588
Print ISSN: 0916-8516
Type of Manuscript: Special Section INVITED PAPER (Special Section on Innovative Superconducting Devices and Their Applications)
ultrafast optical interface,  amorphous Ge,  photomixing,  Josephson vortex flow transistor,  

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Development of ultrafast optical interfaces that can operate in sub-terahertz region is important to apply superconducting electronic devices to the high-end systems. We have performed several fundamental researches to realize the ultrafast optical input interface for superconducting electronic devices. Firstly, we observed optical response of amorphous Ge thin films, and the results indicated that an amorphous Ge photoconductive switch could stably operate in a terahertz frequency range as an optical-to-electrical signal converter in the low-temperature region below Tc of YBCO. Next, we have fabricated optical-to-electrical signal conversion system with photomixing technique, and we have demonstrated the generation and the detection of high frequency signals over 50 GHz. Finally, we have observed optical responses of a Josephson vortex flow transistor under irradiation of femtosecond laser pulses, and the results suggeste that the device has high potential as an optical interface.