Optical spectra of rare‐earth impurity ions in crystalline solids are inhomogeneously broadened in mixed crystal systems. This principle has been used in Y3(Al1−xGax)O12: Nd to lower the cross section of the 1.06‐&mgr;m laser transition by 3.3 relative to Y3Al5O12: Nd, while not substantially altering the thermal conductivity, thereby providing a host for Nd with improvedQ‐switched laser performance. Spectroscopic and paramagnetic resonance studies are reported to elucidate the detailed nature of the broadening.