Co2+:MgAl2O4 Cospinel is a relatively new material for passive Q-switching in lasers
emitting from 1.2 to 1.6 μm, in particular, for eye-safe 1.54 μm Er:glass
laser, but also works at 1.44 μm and 1.34 μm wavelengths. Spinel is a hard,
stable crystal that polishes well. Cobalt substitutes readily for magnesium in
the Spinel host without the need for additional charge compensation ions. High
absorption cross section (3.5×10-19 cm2) permits Q-switching of
Er:glass laser without intracavity focusing both with flash-lamp and diode-laser
pumping. Negligible excited-state absorption results in high contrast of
Q-switch, i.e. the ratio of initial (small signal) to saturated absorption is
higher than 10.
