Accession Number : ADA251387

Title :   Energy Transfer Under Strong Pumping in High Concentration Rare Earth Doped Laser Crystals.

Descriptive Note : Technical rept.,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE CENTER FOR MATERIALS SCIENCE AND ENGINEE RING

Personal Author(s) : Knowles, David S.

Report Date : SEP 1991

Pagination or Media Count : 125

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.

Descriptors :   *CRYSTALS, *OPTICAL PUMPING, *LASER MATERIALS, BEHAVIOR, COUPLINGS, DECAY, DIFFUSION, DIPOLES, EMISSION, EXCITONS, FUNCTIONS, INTERACTIONS, IONS, MEASUREMENT, MODELS, OVERLAP, RATES, SATURATION, STANDARDS, DOPING, PRASEODYMIUM, ERBIUM, ENERGY TRANSFER.

Subject Categories : Radiation and Nuclear Chemistry
      Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE