Luminescence and Faraday rotation properties of Tb2O3 and Tb:Y2O3 single crystals

Abstract

Heavily-doped and fully concentrated 2.78 % Tb:Y₂O₃ and Tb₂O₃ single crystals with high optical quality and very low levels of impurities have been grown and studied for their luminescence and Faraday rotation properties. Absorption, emission and fluorescence decay measurements performed vs excitation wavelength and temperature and their confrontation with Judd-Ofelt and crystal-field calculations show the contributions of two types of luminescent centers: dominant ones with a ⁵D₄ emission lifetime of 23 μs corresponding to coupled near-neighbor Tb³⁺ ions, all in C₂ symmetry sites, and minority ones with a ⁵D₄ emission lifetime of about 2 ms corresponding to coupled Tb³⁺ ions in C₂ and C_3i near-neighbor symmetry sites. Faraday rotation measurements confirm Tb₂O₃ as the Tb-based Faraday crystalline material with the largest ever measured Verdet constant, at all temperatures and from the visible to the near-infrared. They also show that the dominant luminescent centers contribute more particularly to this large Verdet constant thanks to a favorable crystal-field splitting of their ⁷F₆ ground multiplet and also to the contributions of both types of spin-allowed and spin-forbidden 4f-5d absorption bands.