Spatial hole-burning effects in a Nd3+:YAG laser

The concept of spatial hole burning in the population inversion distribution of a solid-state laser was introduced by Tang et al in 1963 [3]. In this paper, several aspects of the spatial hole-burning effect in a CW Nd:YAG laser are discussed, both theoretically and experimentally. The number of oscillating modes, transverse mode degeneracy, and effects of sinusoidal phase perturbations are included. The measured number of oscillating modes is in good agreement with the theory based on the treatments of Tang et al. The transverse mode degeneracy causes an output power dip by quenching higher order modes through the spatial hole-burning effect. The positions of dips are calculated taking into account the thermal focusing effect in a pumped YAG rod. Effects of phase perturbations are discussed using nonlinear rate equations, and it is shown that two kinds of resonances peculiar to the Nd:YAG laser can be excited by a subharmonic sinusoidal drive.