Energy Transfer Under Strong Pumping in High Concentration Rare Earth Doped Laser Crystals.
Abstract
The weak interaction between isolated Er ions, and between Er and Pr ions, has been quantitatively measured in the host crystal BaY2F8. Fluorescent decay data from samples doped with 1%-100% Er and 0.05%-0.5% Pr show the decay rate is linearly proportional to the acceptor (Pr) concentration for all samples, and linearly proportional to the donor (Er) concentration for 5% Er or less, as predicted by the standard dipole-dipole coupling model. For Er concentrations greater than 2O%, the decay has a much stronger dependence on the Er concentration, indicative of a strong short range coupling mechanism (higher order multipole or superexchange) operating between nearest neighbor ions. The dipole-dipole interaction strengths for Er-Er and Er-Pr transfer have been measured for the 4I13/2' 4I11/2' and 4F9/2 levels, and the exciton diffusion rate is calculated as a function of the Er concentration. The upconversion interaction rate between excited Er ions has also been determined for 5%-100% Er:BaY2F8. The results show behavior similar to previous measurements of upconversion in Er:LiYF4: the 4I11/2 upconversion strength increases with Er concentration, and the 4I upconversion strengths upconversion strength saturates at roughly 20% Er. The measured 1/2 the same Er dependence as the Er-Pr transfer, indicating that the increase at high concentrations is due to the same short range interaction mechanism. The 4I13/2 saturation is thought to be due to a bottleneck for Er-Er transfer due to the poor overlap of the Er 4I13/2 emission and excited state absorption.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1991
- Accession Number
- ADA251387
Entities
People
- David S. Knowles
Organizations
- Massachusetts Institute of Technology