Abstract

Sensitization of Tm³⁺ emission in garnets by energy transfer from Fe³⁺ in tetrahedral sites could be an efficient way to improve the efficiency of the system. The tetrahedral sites offer advantages over the octahedral sites for sensitizers (S): the packing around the dodecahedral sites occupied by the rare-earth activators (A) is more compact than for the octahedral sites; the shorter S-A distance is smaller; and the center lacks inversion, thus favoring the electric dipole transitions. Fe³⁺ could occupy in garnet lattices both the octahedral (a) sites and tetrahedral (d) ones, but emission was observed only from Fe³⁺ (d).¹ At room temperature the Fe³⁺ (d) emission is dominated by the phonon sideband and usually covers the range from 750 to 850 nm, and has a good superposition on Tm^{3+ 3}H₄ absorption. The excitation spectra for this emission shows several bands in visible, due to intraconfiguration 3d⁵ transitions. A very intense band peaking around 250 nm could be also used for excitation of Fe³⁺ emission.

© 1994 IEEE