Continuous 30 mu W terahertz source by a high-T-c superconductor mesa structure

Using a modified mesa structure of high-T-c superconducting Bi2Sr2CaCu2O8+delta with a thin underlaying base superconductor (similar to 3 mu m), the effective working temperature of the continuous and monochromatic terahertz emitter is extended up to 70 K, and the maximum power of similar to 30 mu W at 0.44 THz is achieved at the relatively high temperature of T-b = 55 K in a low bias current retrapping region. The diverging behavior of the intensity occurring at 55 K in the low current regime without hot spot formation may provide us an important clue for the stronger THz radiation from intrinsic Josephson junction devices