High-speed and single-shot terahertz spectroscopy using a wavelength-tunable source [Invited]

To realize practical applications of terahertz (THz) waves, it is crucial to establish high-speed and real-time spectroscopic techniques. Although single-shot spectroscopy based on THz time-domain spectroscopy (THz-TDS) has been extensively studied, reports on fast spectroscopy using wavelength-tunable THz sources remain limited. In this paper, we overview the characteristics of various wavelength-tunable sources and introduce recent advancements in high-speed and single-shot THz spectroscopy based on parametric sources. Three approaches are explored: (1) high-speed wavelength sweeping and switching, (2) simultaneous multi-wavelength generation, and (3) quasi-single-shot spectroscopy using pulse trains. Additionally, we present a real-time sample identification method using machine learning, applicable to all three approaches. This enables real-time spectral identification and visualization of reagent distributions with high dynamic range. Our methodology is expected to extend the applicability of THz spectroscopy to new domains that have been challenging for conventional systems.