We find that soft-aperture Kerr-lens mode locking (SAKLM) in a Ti:sapphire laser always takes place around certain discrete cavity configurations accompanied by peculiar beam patterns. By correlating the superposition of proper transverse modes to the observed beam patterns and fitting the beat frequencies to the resonance equation, we discovered that the patterns for SAKLM are formed by phase locking of the fundamental mode with specific degenerate transverse modes that occur near different degenerate cavity configurations. As predicted by the stability analysis, period-3 and period-2 SAKLM does occur around the 1/3- and 1/4-degenerate cavity configurations, which cannot be fully explained in terms of total mode locking of TEM<sub>00</sub> and TEM<sub>01</sub> modes.
© 2001 Optical Society of America
(140.1540) Lasers and laser optics : Chaos
(140.3410) Lasers and laser optics : Laser resonators
(140.3580) Lasers and laser optics : Lasers, solid-state
(140.4050) Lasers and laser optics : Mode-locked lasers
(190.3270) Nonlinear optics : Kerr effect
Ja-Hon Lin, Ming-Dar Wei, Wen-Feng Hsieh, and Hsiao-Hua Wu, "Cavity configurations for soft-aperture Kerr-lens mode locking and multiple-period bifurcations in Ti:sapphire lasers," J. Opt. Soc. Am. B 18, 1069-1075 (2001)