IMPROVEMENTS TO THE ROBUSTNESS OF A TI:SAPPHIRE-BASED FEMTOSECOND COMB AT NPL

This paper reports a number of improvements to a Ti:sapphire-based frequency comb. Changes to the spectral broadening set up, f.2f self-referencing arrangement and servo system are described, including a novel scheme for group-delay dispersion compensation using Wollaston prisms. In combination, these changes improved the signal-to-noise ratio of the carrier-envelope offset beat by 15 dB and increased its frequency stability by more than four orders of magnitude, as well as enabling it to be locked continuously for many hours without optical adjustment.