Development of Saturable Absorbers for Laser Passive Q‐Switching near 1.5 μm Based on Transparent Ceramic Co 2+ :MgAl 2 O 4

We describe the development of a reasonable cost Co 2+ : MgAl 2 O 4 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 4 A 2 ( 4 F) → 4 T 1 ( 4 F) transition of Co 2+ substituting Mg 2+ ions in their T d symmetry sites. The measured ground‐state absorption cross section σ gs = 2.9 × 10 −19 cm 2 , saturation contrast γ = 0.12, and depleted ground‐state recovery time τ 2 = 110–430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as . The spin‐orbit splitting constant was estimated as ξ SL ≅−150 cm −1 for the 4 F parent ground state, and ξ SL ≅ –575 cm −1 for the 4 P 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.