Energy-level structure and spectral analysis of Nd3+(4f3) in polycrystalline ceramic garnet Y3Al5O12

Abstract

A detailed crystal-field splitting analysis is given for the 26 lowest-energy multiplet manifolds, LJ2S+1, of Nd3+(4f3) in polycrystalline ceramic garnet Y3Al5O12 (YAG). The absorption spectra obtained between 8K and room temperature, and between 1750 and 350nm, and the fluorescence spectrum obtained at 8K and observed between 1450 and 875nm are analyzed for transitions between individual energy (Stark) levels that characterize the energy-level structure of Nd3+ ions in D2 symmetry sites, replacing Y3+ ions in the garnet host lattice. A model Hamiltonian including atomic and crystal-field terms is diagonalized within the complete 4f3SLJMJ basis set which includes 364 states. The calculated splitting of the Nd3+ energy levels by the crystal field is compared with the experimental splitting observed in both the ceramic sample and a single-crystal laser rod. Both samples have approximately the same Nd3+ concentration, about 1at.%. By varying the atomic and crystal-field parameters, we obtain a standard deviation of 18cm−1 between 106 calculated-to-observed Stark levels found between the ground state and the D1∕24 at 28 369cm−1. Within this standard deviation the energy-level structure of Nd3+ is found to be similar in both samples. Low temperature visible and near IR spectra of ceramic Nd3+:YAG show it has comparable properties to the crystalline analog.