Coherent heterodyne time-domain spectrometry covering the entire “terahertz gap”

TLDR

Terahertz waves (0.3–10 THz) enable unique sensing and imaging, but achieving simultaneously intense, broadband, and coherent spectroscopic measurement remains challenging. The study reports a spectrometer that uses gas ionization by femtosecond pulses to generate and sense broadband terahertz pulses. The spectrometer employs gas ionization by femtosecond pulses, a recycled optical probe beam, and coherent detection to achieve high field strength and time‑resolved measurement. Using coherent heterodyne detection, the instrument spans the terahertz gap, delivering at least 10 % of maximum signal across 0.3–10 THz.

Abstract

Terahertz waves, electromagnetic radiation in the spectral region commonly defined between 0.3 and 10THz, allow innovative sensing and imaging techniques that can provide spectroscopic information unavailable at other wavelengths. However, simultaneously intense, broadband, and coherent spectroscopic measurement remains challenging. We report spectrometry using gases ionized by femtosecond pulses to generate and sense broadband terahertz pulses. Using a coherent heterodyne technique, the measurements span the “terahertz gap” with ⩾10% of the maximum signal from 0.3to10THz. This spectrometer, using a recycled optical probe beam and coherent detection, offers a high field strength and time-resolved measurement.