Bi2Sr2CaCu2O8 Intrinsic Josephson junctions as coherent THz emitters

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There is still a lack of good active or passive devices operating in the Terahertz (THz) range. Such devices would open a window to applications like non-destructive imaging for materials testing or medical diagnosis, or to novel spectroscopic studies of materials and molecules. Stacks of intrinsic Josephson junctions made of the high temperature superconductor Bi2Sr2CaCu2O8 have recently been shown to operate in this regime. The objective of the present proposal is to investigate THz emission from intrinsic Josephson junction stacks. The goals are twofold: On the one hand we want to understand and model the mechanism of THz generation. Particularly, in the high bias regime where a hot spot and a cold region producing the THz radiation coexist, the mechanism of THz generation is not understood well. A detailed understanding will be necessary to find limits on, e.g., the maximum emission power and the minimum linewidth that can be achieved either for single stacks or for arrays of stacks. The second task is to optimize THz emission from intrinsic junction stacks on experimental grounds and offer demonstrations of applications (e. g. in terms of spectroscopy or THz imaging). Both parts will be performed in close collaboration between the groups of H. B. Wang (National Institute of Material Science, Tsukuba and Research Institute of Superconductor Electronics, Nanjing), V. P. Koshelets (Kotel'nikov Institute of Radio Engineering and Electronics, Moskau) and the applicant.