Beat-frequency sub-terahertz generation via photomixing using dual continuous-wave multimode laser diodes

Terahertz time-domain spectroscopy (THz-TDS) is an advanced technique for material evaluation. TDS commonly uses femtosecond pulsed lasers as the light source. Recent studies have shown that continuous-wave multimode laser diodes (CW-MLD) can be an effective complementary choice. However, CW-MLD-TDS has a discrete spectral shape with fixed frequency peaks. In this research we constructed a THz-TDS driven by dual MLDs and achieved control of internal longitudinal mode frequencies by regulating MLD temperatures. This enabled the generation and tuning of new components corresponding to the beat frequencies of longitudinal modes between MLDs. This advancement will enhance the practicality of MLD-THz-TDS for spectroscopic analysis.