Development of high temperature superconductor terahertz emitter excited by ultrashort laser pulses

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The aim of this project is to develop a highly efficient terahertz emitter made of high temperature superconductors based on the effect of terahertz radiation excited by femtosecond laser pulses. To clarify the radiation characteristics and to apply the terahertz radiation to various fields are also the purposes of the project The following results are obtained by the project.1. By the improvement of the high-Tc superconductor thin films and the antenna structure, the radiation power reached 10 μW with 100 mW excitation. This radiation power competes with that from the semiconductor photoswitches, and therefore the main purpose of the project is attained.2. By the detailed measurement of the characteristics of the radiation, we proposed the radiation mechanism based on the ultrafast supercurrent modulation.3. We proposed and demonstrated the supercurrent visualization by the laser excited terahertz radiation.4. A new superconducting optical magnetic flux trap memory is proposed and demonstrated.5. A very cheap subterahertz spectroscopic system using a CW multimode laser diode and photoswitch is developed.6. We made a time domain terahertz spectroscopic system and applied it to the characterization of semiconductors.