SITE-SELECTIVE EXCITATION AND POLARIZED ABSORPTION-SPECTRA OF ND3-5(PO4)(3)F AND CA-5(PO4)(3)F( IN SR)

Polarized absorption and fluorescence spectra were analyzed to establi sh individual energy (Stark) levels of Nd3+ ions in host crystals of S r-5(PO4)(3)F (SFAP) and Ca-5(PO4)(3)F (FAP). Site-selective excitation and fluorescence facilitated differentiation between Nd3+ ions in emi tting sites-associated with 1.06 mu m stimulated emission, and nonemit ting Nd3+ ions in other sites. Measurements were made on samples conta ining different concentrations of Nd3+ at 4 K and higher temperatures. Substitution of Nd3+ for Sr2+ or Ca2+ was accompanied by passive char ge compensation during crystal growth. Crystal-field splitting calcula tions were performed according to site for Stark levels of Nd3+ ions i dentified spectroscopically. We obtained a final set of crystal-field parameters B-nm for Nd3+ ions in fluorescing sites with a rms, deviati on of 7 cm(-1) (52 levels in Nd:SFAP) and 8 cm(-1) (59 levels in Nd:FA P). For one of the nonemitting sites in Nd:FAP we obtained a final set of B-nm parameters which gave a rms deviation of 6 cm(-1) between 46 experimental and calculated levels. (C) 1996 American Institute of Phy sics.