Erbium–bismuth-doped germanium silicate active optic glass for broad-band optical amplification

This work deals with research and optimization of the optical Ge–Si glass composition doped with Er3+, Yb3+ ions and bismuth optically active centers (BACs), which are optically active for implementation in a double C- and U-band planar optical amplifier. The intention was to increase the range of amplified wavelengths in the NIR band up to 1650 nm. Various types of glass with different content of GeO2, SiO2 and Er2O3, Yb2O3 ions Bi2O3 were prepared and the luminescence response in the 1500–1700 nm range was tested. The maxima of the luminescence intensity in the optical bands and the spectral full width at half maximum (FWHM) were determined by modified reflex spectrum method measurement. The prepared Ge–Si glass doped with Er3+ ions and BACs exhibited strong and balanced emission in the 1520–1680 nm range after pumping at 1480 nm. The specific balanced differential gain of up to 0.2 dB/cm in the C-band and simultaneously 0.2 dB/cm in the U-band was measured. Our results proved that the luminescence of BACs depends on the presence of optical active Er3+ ions and germanium in matrix of glass, pumped by radiation 1480 nm and energy transfer from erbium to BACs have been newly observed in the Ge–Si glass. It has also been found that high content of germanium, comparable with silicon content is required for this transfer. The results show that the germano-silicate glass doped with Er3+ and Bi ions is a perspective material for the fabrication of broad-band amplifiers in the C- and U-bands. •The germano-silicate glass composition containing Er3+, Yb3+ ions and bismuth optically active centers (BACs) was prepared.•Simultaneous emission in investigated bands, i.e. at 1530–1560 and 1620–1680 nm, was evident when pumping 1480 nm was used.•Energy transfer from Er3+ ions to bismuth active centers in the germano-silicate glass is probable.•High content of GeO2 is required for formation of BAC-Ge centers and emission in 1620–1680 nm band.