THz Spectroscopy Using a Free-Running Dual-Comb Fiber Laser

Coherent spectroscopic techniques in the terahertz (THz) region enable a wide range of specialized and industrial applications. Among these techniques, photonic-based THz time-domain spectroscopy (THz-TDS) has been extensively used to study diverse samples, including the rotational transitions of polar gas molecules and opaque film materials, owing to the practicality of its photoconductive antenna (PCA), which is pumped by femtosecond lasers. A well-established THz-TDS scheme employs pump and delayed-probe pulses from the laser to generate and detect THz radiation, respectively. However, this approach faces a trade-off between spectral resolution and data acquisition time owing to the mechanical moving stage.