Spectroscopic properties of Er³⁺-doped barium phosphate glasses for optical gain media

Barium metaphosphate glasses (PBaLa) doped with erbium (Er3+) ions have been prepared by melt quenching method and studied their optical, structural characteristics by using FT-IR, absorption, radiative de-excitation spectra, decay curves and up-conversion measurements. Judd-Ofelt (Omega(lambda), lambda = 2,4 and 6) parameters have been determined using the absorption transitions of the Er3+(1.0 mol %)-doped glasses which are in turn taken to predict the radiative characteristics that include branching ratio (beta(R)), radiative emission probability (A(R)) and lifetime (tau(R)) of some important fluorescent levels of Er3+:glasses. Visible emission spectra measured under 378 nm excitation reveals three emission transitions at 663 (F-4(9/2) -> I-4(15/2)), 547 (S-4(3/2)-> I-4(15/2)) and 524 nm (H-2(11/2) -> I-4(15/2)) corresponding to Er3+ ions. Among these, the green emission at 547 nm is relatively intense. Near-Infrared emissions were measured by exciting at 980 nm which exhibits broad emission at I-4(13/2)-> I-4(15/2) (1.53 mu m). The stimulated emission cross-section (sigma(emi))(,) FWHM and gain bandwidth (sigma(emi) x FWHM) were predicted to be 13.58 x 10(-21) cm(-2), 59 nm and 801.2 cm(3), respectively, for PBaLaEr1.0 glass. The lifetime of I-4(13/2) level has been shortened from 2.53 to 0.8 ms with an increase in Er3+ ions concentration from 0.1 to 2 mol %. NIR to visible up-conversion has also been measured for various concentrations of Er3+-doped PBaLaEr glasses with 980 nm excitation. These findings indicate that the Er3+-doped PBaLaEr glasses can be considered for waveguide laser and optical amplifier applications at 1.53 mu m.