Composition dependence ofND3+optical homogeneous linewidths in crystals

Room-temperature optical homogeneous linewidths of the ${}_{}{}^4{}_{}{}^{}F_{\frac{3}{2}}^{}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}I_{\frac{4}{2}}^{}{}_{}{}^{}$ transition of ${\mathrm{Nd}}^{3+}$ in various crystals are examined as a function of host sound velocity. With the assumption of a Raman broadening process operating in the high-temperature regime, a dependence of the linewidth on the fifth power of the sound velocity is expected. The linewidths are seen to be dependent on the 4.5 power of the sound velocity; deviations from theory occur due to uncertainties in the sound velocity and variations in the strength of the matrix elements of the transition from host to host. This result is compared to the sound-velocity dependence of the linewidths in ${\mathrm{Nd}}^{3+}$ glass systems, which shows that the Raman process is dominant there as well.