fast saturable uv absorber

The problem of mode-locking a fully relaxing saturable (dye) laser medium by an instantaneously saturating (fast) UV Absorber is theoretically considered when group velocity dispersion and Kerr-type nonlinearity are present. Off-resonant chirped solutions are found whose minimum duration is determined by the relative losses (saturable and nonsaturable) and by the saturation depth of the uv absorber. The addition of nonlinear elements can only broaden the stability range of the solution with respect to the group velocity dispersion.