Passive mode locking of a femtosecond Ti : sapphire laser with pulsed synchronous pumping by a finite train of picosecond pulses

An analysis is made, with the aid of the self-consistent nonlinear ABCD mat rix method, of the specific features of the mechanism of passive mode locki ng of a femtosecond Ti:sapphire laser under conditions of pulsed synchronou s pumping. The conditions of stable laser operation are studied. It is prop osed to use an additional aperture as an element of negative feedback for t he stabilisation of passive mode locking. Practical recommendations concern ing the optimisation of a femtosecond laser are given.