Development of Saturable Absorbers for Laser Passive Q-Switching near 1.5 m 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 m domain. The main relevant material characteristics were measured. The absorption band, positioned between 1.2 and 1.7 m, is typical of the (4)A(2) (F-4) T-4(1) (F-4) transition of Co2+ substituting Mg2+ ions in their T-d symmetry sites. The measured ground-state absorption cross section sigma(gs) = 2.9 x 10(-19) cm(2), saturation contrast = 0.12, and depleted ground-state recovery time (2) = 110-430 ns render such parts suitable for the intended application. The radiative lifetime was estimated as 2rad=14.25 mu s. The spin-orbit splitting constant was estimated as (SL)-150 cm(-1) for the F-4 parent ground state, and (SL) -575 cm(-1) for the P-4 parent excited state. Obtained specimens had a transmission of similar to 80% (t = 2 mm, = 600 nm) and included some opaque, white spots. Further improvement of host optical transmission and resistance to laser damage are necessary.