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. The first method is based on the transformation of THz radiation to near-infrared radiation and visualization with a thermograph. The second method is 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 were performed on a 100 W continuous Novosibirsk terahertz free electron laser.