Optical properties including radiative quantum efficiencies, cross-relaxation coefficients, refractive index, energy-gap law parameters, and maximum phonon energy are presented for a new low-phonon-frequency, nonhygroscopic host crystal potassium lead chloride (KPb<sub>2</sub>Cl<sub>5</sub>) doped with Dy<sup>3+</sup> and Nd<sup>3+</sup>. Assuming that the total decay rate (<i>W</i>) from each level is composed of radiative (A<sup>rad</sup>), multiphonon (W<sup>MP</sup>), and concentration-dependent cross-relaxation (W<sup>c</sup>) rates (W=A<sup>rad</sup>+W<sup>MP</sup>+W<sup>c</sup>), we determined radiative quantum efficiencies (η<sup>rad</sup>=A<sup>rad</sup>/W) from emission data for five samples of various Dy<sup>3+</sup> concentrations (N<sub>0</sub>). These results were compared with values calculated from a Judd–Ofelt analysis of the absorption spectrum. This technique required identification of cross-relaxation pathways. A cross-relaxation coefficient k=1.83×10<sup>−37</sup> cm<sup>6</sup> s<sup>−1</sup> (where W<sup>c</sup>=kN<sub>0</sub><sup>2</sup>) was measured for the Dy<sup>3+</sup> <sup>6</sup>H<sub>9/2</sub>+<sup>6</sup>F<sub>11/2</sub> level. The measured multiphonon decay rates yielded energy-gap law (W<sup>MP</sup>[ΔE]≈B exp[−βΔE]) parameters B=3.72×10<sup>9</sup> s<sup>−1</sup> and β=1.16× 10<sup>−2</sup> cm, indicating that laser action should be possible to near 9 μm (ΔE=1100 cm<sup>−1</sup>) in this laser host at room temperature.
© 2001 Optical Society of America
(140.3380) Lasers and laser optics : Laser materials
(140.3580) Lasers and laser optics : Lasers, solid-state
(140.5680) Lasers and laser optics : Rare earth and transition metal solid-state lasers
M. C. Nostrand, R. H. Page, S. A. Payne, L. I. Isaenko, and A. P. Yelisseyev, "Optical properties of Dy3+- and Nd3+-doped KPb2Cl5," J. Opt. Soc. Am. B 18, 264-276 (2001)