Spectroscopy and Imaging by Laser Excited Terahertz Waves

Abstract

Recently, the technology of generating and detecting terahertz (THz) waves by using ultrashort pulse lasers has made great progress. In this paper, we describe THz spectroscopies and imaging with the intention of applying them to diagnostics of plasmas in the future. After a brief description of the method of generating and detecting THz pulses with a femtosecond laser, the principle of THz time-domain spectroscopy is described. The THz magneto-optical effect measurement system up to the magnetic field of 10 T and down to 5 K is also shown. These systems are used to characterize solid state plasmas in semiconductors. The transmission- and reflection-type imaging systems are described and some examples of measurements are shown. Finally, the application of the THz technology to fusion plasma diagnostics is proposed.