High-speed terahertz time-domain imaging

Abstract

Terahertz (THz) imaging based on time-domain spectroscopy is a powerful tool with broad applicability, enabling the inspection of optically opaque multicomponent objects and the identification of several inorganic and organic compounds via their spectral signatures. Yet, it is typically hampered by the long acquisition time required to scan the object pixel by pixel and, for each spatial point, record the THz electric field in time using a delay line. To address this issue, we first implemented a time-domain single-pixel imaging configuration that avoids spatial scanning and allows the use of compressed sensing for faster reconstruction. We then integrated a single-shot THz waveform detection scheme into this system. By appropriately exploiting THz wave diffraction, time-to-space encoding applied to THz point detection enables rapid recovery of the THz waveforms for each pixel of the image. In proof-of-concept experiments, this imaging technique was used for the field-resolved characterization of 3D-printed THz optics, as well as for monitoring reversible and irreversible processes. Video-rate time-of-flight and hyperspectral image acquisition was demonstrated.