| Abstract: | 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. |
