Abstract

Different schemes for mid- IR lasing in the range of 4.1-7.4 μm were investigated in the Pr³⁺, Nd³⁺, Dy³⁺, Ho³⁺, Er³⁺, and Tm³⁺ doped crystals including cooperative excitation and energy sensitization in the co-doped matrices. Theoretical criteria for effectiveness of laser scheme based on Judd- Ofelt theory of radiative electro- dipole transitions and nonlinear theory of multiphonon relaxation have been developed. To determine the effectiveness of laser generation for the mid IR transitions the regularities of multiphonon relaxation (MR) rates of rare- earth ions on the number of phonons n, on the cation atom mass and dimension of unit size (a parameter) of a crystal lattice were investigated. Having this in mind the kinetics of fluorescence decay of the ⁴I_9/2 initial laser level of erbium was measured at 77 and 300K under direct laser excitation in the CaF₂, CdF₂, SrF₂, PbF₂ and BaF₂ crystals and in the crystals co-doped with Y³⁺ or Yb³⁺. The equation for the phonon factor of crystal matrix η depending on the cation mass, the crystal unit dimension (a parameter) and maximum phonon frequency ω_max of crystal lattice as well as a single frequency approach of the spectral phonon density of states of crystal lattice were used.

© 2001 EPS