An optical spectroscopic study of Er-related luminescence in O- and Er-doped samples was performed as a function of temperature and applied hydrostatic pressure. The appearance of various Er-related luminescences was observed under hydrostatic pressure. The temperature dependence of this luminescence intensified for 3 types of Er center, as a function of pressure, was measured and was explained in terms of the trap levels which were formed by the Er centers. It was shown that energy-transfer between photo-excited carriers in the host, and the 4f shell of the Er3+ ion, could occur when trap levels that were associated with an Er center entered the band-gap under an applied hydrostatic pressure.

R.A.Hogg, K.Takahei, A.Taguchi: Physical Review B, 1997, 56[16], 10255-63