Compositions and heat treatment conditions were determined at which absorption and
luminescence properties of aluminosilicate transparent glass-ceramics are defined mainly by
tetrahedrally coordinated Co2+ ions located in spinel nanocrystals. Optical properties of cobaltdoped
aluminosilicate transparent glass-ceramics have been studied in visible – near infrared (IR)
spectral range. It was demonstrated that the concentration of tetrahedrally coordinated Co2+ ions in
the spinel nanocrystals is determined by the CoO content in the initial glass and is independent of
the heat-treatment schedule. Absorption saturation and bleaching relaxation under excitation of the
4A2→4T1(4F) transition of tetrahedrally coordinated Co2+ ions were studied. The value of groundstate
and excited state absorption cross-sections of tetrahedrally coordinated Co2+ ions was
estimated. Comparative study of output pulse parameters of Q-switched Er:glass laser using cobaltdoped
glass-ceramics and Co2+:MgAl2O4 single crystal is presented.