Imaging techniques for a high-power THz free electron laser

Imaging in the terahertz spectral range is a subject of special interest for many applications. In this paper we describe two methods for the THz imaging with a high power free electron laser. First method based on the transformation of THz radiation to near-infrared radiation and visualization with a thermograph. The second method based on the record of the visible light phase shift that appears due to heating of an optically transparent, but opaque in terahertz, medium. The experiments had performed on 100 W continuous Novosibirsk terahertz free electron laser. 1