Calculation of Phase Aperture Kerr-Lens Mode-Locking

Kerr-lens mode locking (KLM) provides broadband large modulation effect with a low non-saturable loss and a high damage threshold which is important to obtain high power and short pulse mode-locked solid-state lasers. The disadvantage of the KLM is that its resonator needs to be aligned close to unstable region in order to increase the effect of KLM on the resonator mode size (modulation depth) that exhibits long term stability and self-starting property. There are two well-known KLM methods, the first one is Hard Aperture (HA) KLM [1] that is based on loss modulation with a real pinhole like obstacle inside the resonator (Fig. 1a). The second one is Soft Aperture (SA) KLM [2] that is based on gain modulation by improvement of mode matching between pump and cavity modes in the gain medium (Fig. 1b). Here we propose and calculate a new method, named phase aperture Kerr-lens mode locking (PAKLM, Fig. 1c).