LUMINESCENCE OF F+ CENTERS IN CAO CRYSTALS UNDER PULSED-LASER EXCITATION

Luminescence of F+ centers (oxygen vacancies each with one electron) has been investigated in thermochemically reduced, electron-irradiated, and neutron-irradiated CaO crystals. Time-dependent emission spectra following laser excitation into the F+ absorption band at 351 nm were measured for the three types of crystals. We observed a fast component with a lifetime less-than-or-equal-to 10 ns and a slow decay attributed to charge trapping and transport. The intensity and decay kinetics of the F+ phosphorescence depended on the method by which the defects had been produced. Estimated gain coefficients for stimulated emission under pulsed laser pumping are less than 0.1 cm-1. These values are significantly smaller than the absorption coefficient at the emission wavelength.