Study on enhancement of coherent THz radiation using electron beam tilting

The terahertz wave is located in the intermediate frequency band between radio waves and light waves, and the development of light sources, detectors and the like is not be matured compared to those. Recently, with the development of femtosecond laser and photoconductive switching technology, studies of terahertz wave are becoming popular, and we propose the possibility of coherent THz radiation using the tilt control of electron beam as a new terahertz light source. Cherenkov radiation emitted when high speed charged particles exceed the light velocity in the medium has a peak at an angle depending on the refractive index of the medium. Coherent radiation can be realized by controlling the tilt of the electron beam with high precision and making it coincide with this Cherenkov radiation angle. In this method, it is necessary to investigate the relationship between the length that the electron beam moves in the medium and the number of photons emitted per unit length, and to optimize the target medium. High intensity THz light can not be obtained by previous research using silicon as a medium having higher density and higher refractive index. Therefore, THz light intensity was compared by using silica aerogel as a low-density medium. In this presentation we report on the experimental results of optimization of these target media and future prospects. (author)