Passive mode-locking of Q-switched solid state lasers using low frequency stimulated Brillouin scattering in birefringent crystals

Successful mode locking of a Q-switched ruby laser using a birefringent crystal as an intracavity element is demonstrated. Intense elastic waves are generated inside a birefringent crystal through the low frequency stimulated Brillouin scattering process and these in turn modulate the refractive index of the crystal and thus provide the necessary phase synchronization for spontaneous phase locking. Strong coupling between several neighboring modes of the laser is introduced by this SBS technique. It is shown that large depth of modulation is provided by the SBS process and it is concluded from the observations that such large depth of modulation are achieved even for a small crystal length.