INDUCED CHANGE IN THE REFRACTIVE-INDEX OF OPTICALLY-EXCITED Y1.5ER1.5AL5O12 CRYSTALS

We investigate changes in the refractive index of Y15Er15Al5O12 crysta ls at the wavelength of 2.94 mu m, which corresponds to the I-4(11/2) --> I-4(13/2) laser transition between the levels of an Er3+ ion under conditions of resonant excitation of active centers to the I-4(13/2) level. The performed experiments have shown that the polarizability of crystals related to transitions between the levels of f --> d configu rations is equal to Delta alpha(f --> d) d = (1-0.3) x 10(-24) Cm-3, a nd the polarizability related to the resonant laser transition between the I-4(11/2) and (4)I(13/2)levels is Delta alpha f --> = (0.5-1.5) x 10(-22) cm(3).