Herriott Multipass-type Kerr-lens Mode-locked Femtosecond Laser Oscillator

Abstract

A simple Herriott multipass-type femtosecond laser oscillator based on only two notched mirrors without any compensator for q-preserving is presented. Due to the notches, the Herriott multipass cavity acts as a lens with a large effective focal length and is not strict for q-preserving. It is shown that the Kerr-lens mode-locked condition in the Herriott multipass cavity can be retained by using the ABCD transfer matrix containing a self-focusing effect. In this oscillator, we obtained an output power of 2.26 W at a repetition rate of 13.16 MHz and a pulse width of 26 fs, corresponding to an output energy of 172 nJ.