Frequency-comb-based ultrastable terahertz-frequency synthesizer traceable to an optical reference

The terahertz spectral regime finds applications in terahertz spectroscopy and next-generation wireless communications, necessitating improved frequency stability and accuracy. This study presents a novel approach to achieve ultra-stable terahertz continuous-wave generation by referencing an optical cavity using an optical frequency comb. The results demonstrate an extended operating frequency range of 0.1-1.1 THz with frequency stability of about 10⁻¹⁵ at 1 s. This exceptional level of stability has significant implications for terahertz wave research, holding the potential for groundbreaking advancements in both fundamental and industrial applications.