Deformation of picosecond pulses because of two-photon absorption

Rate equations are used to study the influence of a two-photon absorber with a large relaxation time on the shape of picosecond output pulses. This absorber is assumed to be placed in a laser resonator in addition to a one-photon saturable absorber. Numerical methods are used to demonstrate that a 30% reduction in pulse duration (relative to the duration in the absence of the two-photon absorber) can be achieved for selected values of parameters.