Infrared superbroadband emission of Bi ion doped germanium–aluminum–sodium glass

Abstract

The 96GeO–(3- χ)Al 2O 3– χNa 2O–1NaBiO 3 ( χ = 0, 0.5, 1.5 molar percent designated as A1, A2 and A3) and 96GeO–(3.5- ψ)Al 2O 3– ψNa 2O–0.5Bi 2O 3 ( ψ = 0.5, 1, 2 molar percent designated as B1, B2 and B3) glasses were prepared by conventional melting method with the measurement of their DTA curve, fluorescence decay curve, transmission, absorption and emission spectra. The near infrared superbroadband emission characteristics of the A1, A2, B1 and B2 glasses peak at ∼1220 nm were observed when pumped by an 800 nm laser diode. The stimulated emission cross section ( σ p) was obtained from the emission spectra. The result indicated that the introduction of Bi 5+ in NaBiO 3 into raw materials could increase the emission intensity of the obtained glasses by 5.6 times than that of Bi 3+ in Bi 2O 3, and the FWHM (Δ λ) and emission lifetime ( τ) at 1220 nm increased from 195 nm to 275 nm, and 280 μs to 434 μs. Meanwhile, it was found that the absorption edges were blue-shifted from 486 to 447 nm by comparing those of A1 and B1. The absorption edges were considered to be ascribed to the charge transfer from Bi 3+ 6s 2 to Bi 5+ 6s 0. Therefore we could conclude that the content of Bi 5+ ions in A1 was more than that in B1 glasses. It could be deduced from the emission and absorption spectra that the stronger emission intensity and wider FWHM were due to the higher concentration of Bi 5+ ion in glass. In particular, the increase of Na 2O content was in proportion to the thermal stability and the value of σ p × τ and σ p × Δ λ of glasses.