Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers

摘要

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5?THz quantum cascade laser to a free-space comb, generated in a LiNbO₃ waveguide and covering the 0.1–6?THz frequency range. We show that even a small fraction (. ? 2012 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.