Development of Saturable Absorbers for Laser Passive Q‐Switching near 1.5 μm Based on Transparent Ceramic Co2+:MgAl2O4

We describe the development of a reasonable cost Co2+:MgAl2O4 transparent ceramic plates fabrication technology that allows the producing of parts functioning as passive laser Q-switches in the 1.3–1.7 μm domain. The main relevant material characteristics were measured. The absorption band, positioned between 1.2 and 1.7 μm, is typical of the 4A2 (4F) → 4T1 (4F) transition of Co2+ substituting Mg2+ ions in their Td symmetry sites. The measured ground-state absorption cross section σgs = 2.9 × 10−19 cm2, saturation contrast γ = 0.12, and depleted ground-state recovery time τ2 = 110–430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as τ2rad=14.25μs. The spin-orbit splitting constant was estimated as ξSL≅−150 cm−1 for the 4F parent ground state, and ξSL ≅ –575 cm−1 for the 4P parent excited state. Obtained specimens had a transmission of ~80% (t = 2 mm, λ = 600 nm) and included some opaque, white spots. Further improvement of host optical transmission and resistance to laser damage are necessary.