A Sub-10-fs Ti:Sapphire Oscillator with a Simple Four-Mirror Cavity

(Received 21 December 2007)Optical pulses of 9.4 fs are stably generated from a Kerr-lens mode-locked Ti:sapphire laseroscillator containing only four mirrors, including two double-chirped mirrors. To the best of ourknowledge, the oscillator has the simplest cavity design compared with other sub-10-fs oscillatorsreported yet. The balanced distribution of the negative group delay dispersion within the cavityyields improved stability against intensity uctuations.