PHONON EFFECTS ON SHARP LUMINESCENCE LINES OF ND3+ IN GD3SC2GA3O12 GARNET (GSGG)

The widths, positions and shapes of sharp luminescence lines of the Nd3+ ion in GSGG: Cr3+, Nd3+ were measured carefully from 78 to approximately 600 K. The sharp lines studied correspond to the R2 --> Y1, R1 --> Y1, R2 --> Y3, R1 --> Y2, R2 --> Y6, R1 --> Y6 and R1 --> Z5 transitions. All the lines shift to the red with increasing temperature except for the R1 --> Z5 line which shifts to the blue. The temperature dependence of line widths and line shifts is explained in terms of an ion-phonon interaction as a perturbation and of a Debye phonon distribution. The Debye temperature is treated as an adjustable parameter to get the best fit to the experiment data. The line widths are related to Raman scattering of phonons, direct phonon processes and statistical local strain of the crystal. The line shifts are due to the stationary effect of the ion-phonon interaction. The Debye temperature of GSGG is estimated to be approximately 500 K through the fittings of the theoretical formulas to the experimental data.