Optical characterization, luminescence properties of Er3+and Er3+/Yb3+co-doped tellurite glasses for broadband amplification

Abstract

In the present paper, optical absorption and emission spectra and luminescence decay lifetimes of different concentrations, 0.1, 0.3, 0.5, 0.7 and 1.0 mol% of Er 3+ and 0.1Er 3+ /0.5Yb 3+ co-doped tellurite glasses (TeO 2 -Bi 2 O 3 -ZnONb 2 O 5 ) were reported. Judd-Ofelt intensity parameters were determined and used to calculate spontaneous radiative transition probabilities (A rad ), radiative lifetimes (τ R ), branching ratios (β) and stimulated emission cross-sections (σ P ) for certain emission transitions. NIR emission at 1.5μm and up-conversion spectra of Er 3+ and Er 3+ /Yb 3+ co-doped tellurite glasses were measured under excitation wavelength of 980 nm. The absorption, emission and gain cross-sections for 4 I 13/2 → 4 I 15/2 transition of Er 3+ are determined. The peak emission cross-section of this transition is found to be higher (9.95×10 -21 cm 2 ) for 0.1 mol% of Er 3+ and lower (6.81×10 -21 cm 2 ) for 1.0 mol% of Er 3+ doped tellurite glasses, which is comparable to other oxide glasses. The larger peak emission cross-section for lower concentration of Er 3+ is due to the high refractive index of glass matrix (2.1547), relation established from Judd-Ofelt theory. The observed full-widths at half maxima (FWHM) for lower and higher concentrations of Er 3+ are 64nm and 96 nm respectively. The larger values of FWHM and peak emission cross-sections are potentially useful for optical amplification processes in the design of Erbium doped fiber amplifiers (EDFs). Under 980 nm excitation three strong up-conversion bands were observed at 530nm, 546nm and 665nm. The pump power dependent intensities and mechanisms involved in the up-conversion process have been studied. The luminescence decay profiles for 4 I 13/2 level were reported for all glass matrices.