Gain determination of new erbium-bismuth doped germanium silicate optical glass for double-band optical amplification

Abstract

The research examines the measurement and modeling of gain in optical silica-germanium glass doped with erbium and bismuth activators to implement a two-band planar optical amplification. Including both activators enables bismuth active centers with germanium (BAC-Ge) to broaden amplification across the near-infrared bandwidth, reaching up to 1650 nm, where the optical attenuation in telecommunications fibers is below 0.3 dB/km. We have outlined the amplification mechanism through the luminescence spectral response of the activators. The differential amplification gain of the fabricated active glasses was determined using a pulse measurement method alongside calculating a model based on waveguide propagation equations. A single source with a wavelength of 1480 nm was employed for pumping in both optical bands. The emission and absorption cross-section coefficients were derived from the luminescence spectra of glasses using the Füchtbauer-Ladenburg equation with a Gaussian approximation, along with McCumber's theory. The calculated differential gain values align closely with the measured results. Our findings suggest that the optical activity of BAC-Ge is significantly influenced by germanium doping in the amplification process through BAC-Ge centers.