Co2+:GGG nonlinear optical crystal for the 1.3 — 1.7-μm spectral range

A cobalt-doped GGG crystal is grown and its properties are studied. The absorption and fluorescence spectra in the visible and IR regions are measured. The absorption cross sections of the Co²⁺ ion in the GGG crystal at a wavelength of 1535 nm are determined for transitions from the ground (σ_gs = 4.8 × 10^-20 cm²) and metastable states (σ_es = 1.4 × 10^-20 cm²). Preliminary experimental results on Q-switching of erbium laser radiation by a Co²⁺:GGG passive Q-switch are presented.