Development of a compact THz FTS system

It is well known that the FTS (Fourier Transform Spectroscopy) method, which adopts the direct-detection technique, has rather large frequency coverage. Thus it is a better choice for the measurement of frequency response of submillimeter detectors. In this paper, we present an FTS designed for the frequency range from 0.1 to 5 THz. The transmission property and beam efficiency of the Gaussian beam of the FTS system are characterized.