Significant enhancement of the THz radiation from InAs[100] clean surface at low-temperature

A lot of THz-radiation sources have been intensively studied for applications to sensing or imaging, and a time-resolved spectroscopy. We had demonstrated the significant enhancement of THz-radiation power from InAs under a magnetic field irradiated with femtosecond optical pulses. In this case, the InAs emitter was at room temperature and was kept in the air without any special treatment. For practical light source development, it is meaningful to know some kind of surface treatment will be effective for the enhancement of the radiation intensity, or not. Additionally, it is known that the generation mechanism of THz-radiation from the semiconductors is closely related to its surface. Therefore, characterization of the THz-radiation from well-controlled surface at various temperatures will be interesting from the physics point of view. In this presentation, we report strong enhancement of THz radiation from an InAs irradiated with femtosecond laser pulses after surface cleaning and temperature cooling.