Characteristics of the partially reflected terahertz wave: truncated beam propagation

We investigate a free-space propagation of a truncated terahertz beam created as a result of a partial reflection from a small-sized metallic reflector. By using terahertz time-domain spectroscopy, we obtain both magnitude and phase spectra of a clipped terahertz beam after its propagation by about 15 cm. Compared to a fully reflected terahertz beam, the partially reflected beam exhibits large variations in both magnitude and phase spectra in the entire spectral range investigated, i.e., from 0.2 to 1.3 terahertz. To model the free-space propagation of the truncated Gaussian beam, we decompose it using a super-Gaussian beam and several other Gaussian beams with phase factors separately assigned to each component. From this, we could successfully reproduce the experimental results, i.e., the modulations observed in both magnitude and phase spectra. (C) 2019 Optical Society of America