Source: Website of National Astronomical Observatories, Chinese Academy of Sciences (CAS) ( http://www.bao.ac.cn )
The bandgap voltage and bandgap frequency of super conduct tunnel junction is twice as powerful as that of Nb super conduct tunnel junction, though the latter is mostly used in the field of millimeter and sub-millimeter astronomical observation nowadays. The former enjoys a broader working frequency£¨0.1~2.8THz£©, more wider working temperature range, and higher stability.£¨The interactive effect between quasi particle tunneling characteristics and Josephson effect is weak.£©The exploration and application technology concerned with NbN super conduct tunnel junction has a bright future in observing and researching on earth surface, space and atmosphere at Thz frequency.£¨Signal range and phase can also be inspected.£©However, the coherence length of NbN super conducting thin film is even shorter, which needs thinner ( in Nanometers) barrier in order to realize super conductive effect. Therefore, the R&D of NbN super conduct tunnel junction devices and apparatus as well as explorer manufacture have been a super challenge, technically speaking, for a long time.
The Millimeter and Sub-Millimeter Wave Laboratory in Purple Mountain Observatory of CAS cooperated with Japanese National Institute of Information Communications Technology (NICT), whose devices and apparatus of super-conduct were employed in this cooperation, and succeeded in the development of NbN super conduct tunnel junction explorer at 0.5 THz frequency. It has also been successfully applied in the POST sub-millimeter telescope in Lingha, Qinhai Province, China. The noise temperature of the telescope practical receiving system is 7 times lower than extreme quantum limit. By employing this NbN super tunnel junction concerned explorer, the telescope also successfully observed the sub-millimeter astronomical spectral lines, wavelength 650 micron£¨from the J=4-3 transition of out space molecules, as presented in the following picture£©, from the direction of Orion Molecular Cloud , on Dec. 31st, 2007. It is the first time in the whole world to realize the astronomical observation technically explored by NbN super conduct tunnel junction. It will play a significant role as well in the development and application of THz super conduct exploration technology.