KERR LENS EFFECTS IN A FOLDED-CAVITY 4-MIRROR LINEAR RESONATOR

The Kerr-lens mode locking of a folded-cavity four-mirror linear Ti:sa pphire laser is simulated by applying the ABCD ray-tracing technique f or a Gaussian beam. The intensity dependent Kerr-lens ABCD matrix of t he Brewster-plate shaped active medium is derived. A split-step parabo lic refractive index model is used. The astigmatism compensation condi tion is derived from the ABCD ray-tracing. Simulations are carried out for a symmetric resonator and an asymmetric resonator design. Hard-ap erture loss mode locking and soft-aperture gain mode locking are discu ssed. The optimum design parameters (slit position for hard-aperture l oss mode locking, pump beam focusing for soft-aperture gain mode locki ng, gain cavity spacing, gain medium position) for Kerr-lens mode lock ing are determined.