Passive mode locking in a laser with a Raman active filter

An expression is obtained for the nonlinear susceptibility characterizing coherent mode interaction in a Raman active or SRS (stimulated Raman scattering) filter. It is demonstrated that SRS nonlinearity, along with resonance nonlinearities, can be used for the passive mode locking of a laser. The advantages that the Raman active filter has over a saturated absorber and a resonant medium with a split level are nonselectivity with respect to the laser emission frequency and the absence of losses due to resonance absorption.