Sparse cw-THz Spectroscopy at 1 kHz Measurement Rate

We present sparse sensing with only four terahertz (THz) frequencies enabling fast THz measurement at 1 kHz measurement rate. This is based on a novel method for amplitude and phase determination in homodyne terahertz (THz) spectrometers. Our technique utilizes direct frequency modulation of a distributed feedback laser to precisely measure phase without the need for moving parts or additional phase shifters. We validate our approach by comparing the refractive index and absorption coefficient measurements of an aluminum oxide (AlOx) sample with those obtained from time-domain spectroscopy (TDS). Our findings reveal that our refractive index measurements closely align with TDS results, deviating by less than 1%.