Optical properties of Dy3+- and Nd3+-doped KPb2Cl5

Optical properties including radiative quantum efficiencies, cross-relaxati on coefficients, refractive index, energy-gap law parameters, and maximum p honon energy are presented for a new low-phonon-frequency, nonhygroscopic h ost crystal potassium lead chloride (KPb2Cl5) doped with Dy3+ and Nd3+. Ass uming that the total decay rate (W) from each level is composed of radiativ e (A(rad)), multiphonon (W-MP), and concentration-dependent cross-relaxatio n (W-c) rates (W = A(rad) + W-MP + W-c), We determined radiative quantum ef ficiencies (eta (rad) = A(rad)/W) from emission data for five samples of va rious Dy3+ concentrations (N-0). These results were compared with values ca lculated from a Judd-Ofelt analysis of the absorption spectrum. This techni que required identification of cross-relaxation pathways. A cross-relaxatio n coefficient k = 1.83 x 10(-37) cm(6) s(-1) (where W-c = kN(0)(2)) was mea sured for the Dy3+ H-6(9/2) + F-6(11/2) level. The measured multiphonon dec ay rates yielded energy-gap law (W-MP[DeltaE] approximate to B exp[-beta De ltaE]) parameters B = 3.72 x 10(9) s(-1) and beta = 1.16 x 10(-2) cm, indic ating that laser action should be possible to near 9 mum (DeltaE = 1100 cm( -1)) in this laser host at room temperature. (C) 2001 Optical Society of Am erica.