Temperature dependence of the R1 linewidth in Al2O3:Mn4+: A spectral hole-burning and FLN study

The temperature dependence of the R1 linewidth in Al2O3:Mn4+ is reported. Transient holes broaden rapidly from 2.5 to 40 K due to the one-phonon process between the E ¯ and 2 A ¯ levels of the 2E excited state. The linewidth varies from 3 MHz at 2.5 K to 2640 GHz at 294 K and the line shifts by −1440 GHz. Above 50 K the two-phonon Raman process becomes dominant. The quadratic electron–phonon coupling constant is larger for Al2O3:Mn4+ compared to ruby, resulting in a stronger phonon sideband in Al2O3:Mn4+. The best description of the linewidth data are yielded by a model using pseudo-local modes.