We demonstrate a novel, long, multiple-pass cavity (MPC) to obtain low repetition rates and high peak intensities from Kerr-lens mode-locked lasers. We show that the MPC provides a zero effective length by a unity transformation of the q parameter after a given number of transits of the laser beam. Pulse durations of 16.5 fs with 0.7 MW of power at a 15-MHz repetition rate are achieved. This is, to our knowledge, the lowest repetition rate ever achieved directly from a femtosecond laser resonator without use of additional active devices and cavity dumping. The combination of low repetition rates and high peak intensity is extremely useful for femtosecond pump–probe and other nonlinear experiments because it permits the application of high peak intensity without excessive average power.
© 1999 Optical Society of America
(140.3580) Lasers and laser optics : Lasers, solid-state
(140.3590) Lasers and laser optics : Lasers, titanium
(140.4050) Lasers and laser optics : Mode-locked lasers
(140.7090) Lasers and laser optics : Ultrafast lasers
(320.7120) Ultrafast optics : Ultrafast phenomena
S. H. Cho, B. E. Bouma, E. P. Ippen, and J. G. Fujimoto, "Low-repetition-rate high-peak-power Kerr-lens mode-locked TiAl2O3 laser with a multiple-pass cavity," Opt. Lett. 24, 417-419 (1999)