Mid-infrared Emission Properties of Ho3+-doped Ge-Ga-S-CsI Glasses

A serial of chalcogenide glasses based on Ge-Ga-S-CsI system doped with the different Ho3+ ions were synthesized by meltquenching technique. The properties of glasses including refractive indexes, absorption spectra, midinfrared emission spectra and lifetimes of 5I6 level of Ho3+ ions were measured. The Judd Ofelt intensity parameters Ωi (i=2,4,6), oscillator strength fcal, spontaneous transition probabilities Arad for Ho3+ ion were calculated by Judd-Ofelt theory. Multiphonon relaxation rates of the Ho3+∶5I5→5I6 and 5I6→5I7 in Ge-Ga-S-CsI glasses were evaluated. Effect of Ho3+ ion concentration on the fluorescence spectra was investigated. The results indicate that the fluorescence under 900 nm excitation with peak wavelength at 2.81μm and 3.86μm are due to the Ho3+∶5I5→5I6 and 5I6→5I7 transition, respectively. The intensity of the mid-infrared fluorescence are enhanced with the Ho3+ ion concentration increasing from 0.5wt% to 1.0wt%. Multiphonon relaxation rates are 29s-1 and 34s-1 for the Ho3+∶5I5→5I6 and 5I6→5I7 transition, respectively.