Modulating and scanning the mode-lock frequency of an 800-MHz femtosecond Ti:sapphire laser.

An 800-MHz self-mode-locked femtosecond Ti:sapphire laser has been developed whose mode-lock frequency can be robustly scanned and modulated. The laser is based on the three-element design of Ramaswamy-Paye and Fujimoto [Opt. Lett. 19, 1756 (1994)]. By translation and modulation of the position of the prismatic output coupler, the mode-lock frequency can be reliably scanned more than 1% and modulated at 80 Hz with a deviation of 2.5 kHz without interrupting the mode lock, changing the pulse length, or inducing significant amplitude modulation. An application in tunable high-resolution terahertz spectroscopy is also demonstrated.