Analytical Modeling of Terahertz Time-Domain Spectroscopy with Monolithic Mode-Locked Laser Diodes

In this work, we present an analytical model that links the complex terahertz spectrum acquired with a terahertz time-domain spectroscopy (THz-TDS) system to the complex optical spectrum from a monolithic mode-locked laser diode (MLLD) and the transfer function of the terahertz channel. It also gives the relationship between the optical intensity autocorrelation and the terahertz spectrum. This model greatly improves the understanding of THz-TDS with ultra-high repetition rate lasers and enables the design of lasers with optimized optical spectra.