Coherent detection of pulsed terahertz waves in solid, gaseous, and liquid media.

Coherent detection measures both the amplitude and phase of pulsed terahertz (THz) waves simultaneously, forming the foundation for THz time-domain spectroscopy (THz-TDS). This technique has become increasingly prominent in the fields of physics and materials science, allowing researchers to investigate the dynamic properties of various dielectric materials within the 0.1 to 10 THz frequency range, which is previously a challenging spectrum to access. This paper reviews recent advancements and the challenges faced by commonly used coherent detectors in THz-TDS. Our discussion emphasizes the potential for new discoveries in THz photonics and highlights the crucial role of coherent detection in the study of laser-matter interactions.