Self-modulation of the unsaturated gain in a femtosecond Ti: sapphire laser

Experimental and theoretical investigations were made of self-modulation of the gain in a solid-state continuously pumped femtosecond laser. This self-modulation was due to a change in the characteristics of the radiation as a result of self-focusing in the active medium. The unsaturated gain was calculated for different values of the parameter representing the self-induced Kerr nonlinearity. The optimal conditions for stable mode locking were analysed.