Spectroscopic Study of Double Sodium-Yttrium Fluoride Crystals Doped with Erbium Na_(0.4)Y_(0.6)F_(2.2):Er~(3+): II. Luminescence Self-Quenching and Microparameters and Macrorates of Energy Transfer

摘要

Na_(0.4)Y_(0.6)F_(2.2):Er~(3+) (NYF:Er~(3+)) crystals with an Er concentration up to 15percent were grown by the Bridgman-Stockbarger method. The luminescence kinetics was investigated for a series of NYF:Er~(3+) crystals (0.5-15percent Er), as well as the concentration and temperature quenching of the luminescence from radiative Er levels upon selective laser excitation. It is shown that the luminescence from the ~(4)S_(3/2) level is quenched significantly with increasing temperature and concentration. The luminescence from the ~(4)G_(11/2), ~(2)G(H)_(9/2), ~(4)F_(9/2), and ~(4)I_(9/2) levels is quenched mainly due to nonradiative multiphonon transitions. The concentration quenching of the luminescence from the ~(4)I_(11/2) and ~(4)I_(13/2) levels was not observed. Possible schemes of the self-quenching of excited levels of erbium are considered and the microparameters and macrorates of self-quenching are estimated by model quantum-mechanical calculation. Based on the comparison of the calculated and experimental self-quenching rates, the most probable mechanisms and schemes of self-quenching are determined. The self-quenching of the ~(4)S_(3/2) level of erbium was investigated experimentally and theoretically. Good agreement is obtained between the experimental and the calculated kinetic curves and the dependences of the self-quenching rates on Er concentration. It is concluded that NYF:Er~(3+) crystals are promising as active media for tunable lasers with laser diode pumping.