Cavity configurations for soft-aperture Kerr-lens mode locking and multiple-period bifurcations in Ti : sapphire lasers

We find that soft-aperture Kerr-lens mode locking (SAKLM) in a Ti:sapphire laser always takes place around certain discrete cavity configurations acco mpanied by peculiar beam patterns. By correlating the superposition of prop er transverse modes to the observed beam patterns and fitting the beat freq uencies to the resonance equation, we discovered that the patterns for SAKL M are formed by phase locking of the fundamental mode with specific degener ate transverse modes that occur near different degenerate cavity configurat ions. As predicted by the stability analysis, period-3 and period-2 SAKLM d oes occur around the 1/3- and 1/4-degenerate cavity configurations, which c annot be fully explained in terms of total mode locking of TEM00 and TEM01 modes. (C) 2001 Optical Society of America.