Spectroscopic effects of disorder in laser materials

The inhomogeneous broadening of optical transitions in solids is of fundamental importance in understanding the interaction of optical centres with their environment. In perfect crystals optical linewidths are determined by excited state lifetime and other d-phasing mechanisms such as the electron–phonon interaction. However, in real crystals random differences of impurities in crystallographically equivalent sites result in overlapping transitions and inhomogeneously broadened Gaussian lines. The suppression of inhomogeneous broadening of solid-state spectra using optical hole-burning and fluorescence line-narrowing techniques is discussed in terms of the determination of the homogeneous widths, multi-site geometries and the distributions of spectroscopic parameters that accompany disorder in a number of laser crystals and glasses.