Recent progress on rare-earth doped polycrystalline YAG transparent ceramics has made them an alternative novel solid-state laser gain material. In this paper we present results of our research on polycrystalline RE:YAG transparent ceramics. High optical quality YAG ceramics doped with various rare-earth (RE) ions such as ${\rm Nd}^{3+}$, ${\rm Yb}^{3+}$, ${\rm Er}^{3+}$, ${\rm Tm}^{3+}$, and ${\rm Ho}^{3+}$ have been successfully fabricated using the solid-state reactive sintering method. Highly efficient laser oscillations of the fabricated ceramics are demonstrated.

A Nd:YAG laser oscillator Q-switched and mode locked via a nonlinear mirror based on stimulated Brillouin scattering (SBS) and aided by an acousto optical modulator (AOM) has been realised. A rate equation model and a round trip model are used to describe the longitudinal mode dynamics. Parameter variations of the nonlinear SBS mirror and the loss modulating AOM in the resonator are investigated with regard to their effect on the pulse duration and spectra of the pulses.