Optical properties of Dy^3+- and Nd^3+-doped KPb_2Cl_5

Abstract

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 (KPb2Cl5) doped with Dy3+ and Nd3+. Assuming that the total decay rate (W) from each level is composed of radiative (Arad), multiphonon (WMP), and concentration-dependent cross-relaxation (Wc) rates (W=Arad+WMP+Wc), we determined radiative quantum efficiencies (ηrad=Arad/W) from emission data for five samples of various Dy3+ concentrations (N0). 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=1.83×10-37 cm6 s-1 (where Wc=kN02) was measured for the Dy3+ 6H9/2+6F11/2 level. The measured multiphonon decay rates yielded energy-gap law (WMP[ΔE]≈B exp[-βΔE]) parameters B=3.72×109 s-1 and β=1.16×10-2 cm, indicating that laser action should be possible to near 9 µm (ΔE=1100 cm-1) in this laser host at room temperature.