INVESTIGATION OF RADIATIVE AND NONRADIATIVE TRANSITIONS IN LASER CRYSTALS.
Final rept. 10 Jun 66-10 Aug 67,
RAYTHEON CO WALTHAM MASS RESEARCH DIV
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Spontaneous emission probabilities for magnetic- and electric-dipole transitions from excited states of Pr3, Nd3, Tm3 in LaF3 and Pr3, Nd3, Eu3, Tm3 in Y2O3 are calculated using the treatment of Judd and Ofelt. Intermediate coupled states and empirical intensity parameters were used. The calculated radiative decay probabilities are compared with fluorescence lifetimes measured at low rare-concentrations, where ion pair relaxation is negligible, to predict quantum efficiencies and test the theory. The agreement between radiative and observed lifetimes is generally satisfactory for those low-lying excited states where unit quantum efficiency is expected the agreement is less satisfactory for higher excited states. The approximations and limitations inherent in the approach, possible breakdown of the closure assumption, and effects of the neglect of crystal-field interactions are discussed. A decrease in quantum efficiency with decreasing importance of nonradiative decay by multiphonon emission. A general computational program to calculate energy level schemes, absorption and fluorescence intensities, and quantum efficiencies of rare-earth ions is outlined. Techniques for investigating fluorescence decays in the nanosecond time domain are described briefly. Author
- Lasers and Masers
- Solid State Physics