Relative importance of static contribution to the thermal shifts of spectral lines in Nd~ (3+)-doped Y_ 3Al_ 5O_ (12) laser crystals

摘要

By means of the observed pressure and temperature dependences of several spectral lines in yttrium aluminum garnet Y_ 3Al_ 5O_ (12) (YAG):Nd~ (3+) laser crystals, the static contribution due to lattice thermal expansion and the vibrational contribution due to electron-phonon interaction to the thermal shifts of these spectral lines are studied. It is found that (i) the importance of static contribution of a spectral line depends on the pressure dependence of this line, (ii) the static contribution always leads the spectral lines to shift to the blue (i.e. higher energy) with increasing temperature, while the vibrational one leads the lines to shift to the red, and (iii) the relative importance of static contribution changes not only from crystal to crystal (as suggested in the previous papers for hard or soft crystals), but also from spectral line to spectral line in the same crystal. So, the general statement in previous studies that the static contribution to thermal shift is negligibly small in a hard crystal is inappropriate.