Impact of luminescence quenching on relaxation-oscillation frequency in solid-state lasers

Measurement of the laser relaxation-oscillation frequency as a function of pump rate allows one to determine parameters of the laser medium or cavity. We show that luminescence quenching of a fraction of the rare-earth ions in a solid-state laser affects the relaxation oscillations, resulting in incorrect values for the parameter deduced from this measurement. In the equations describing the relaxation oscillations, we replace the lifetime of the upper laser level by an effective lifetime that takes the luminescence quenching into account. In an Al2O3:Yb3+ distributed-feedback laser we observe significant quenching, with the effective lifetime being ~18 times shorter than the intrinsic upper-laser-level lifetime.