Compensation of Incomplete Round Trip in an Herriott Multipass-Based Kerr-Lens Mode-Locked Ti:Sapphire Oscillator via an Output Coupler Position

Abstract

We examined the soft-aperture Kerr-lens mode-locked femtosecond Ti:sapphire oscillator derived from an Herriott multi-pass cavity (HMPC). Additionally, a novel and simple configuration was provided to extend the cavity length, the HMPC consisting of notched, flat and curved (R 4 m) mirrors by which beams were injected and extracted. To compensate for beams which failed to complete round trips, the configuration was designed and analyzed as a function of the output coupler position. Such an oscillator generated 21.5 nJ, 34 fs pulses at a repetition rate of approximately 13.5 MHz; the spectral bandwidth represented 20 nm, corresponding to a time-bandwidth product of 0.33, assuming a sech(2) fit. (C) 2011 The Japan Society of Applied Physics