Phase-Separated Alumina–Silica Glass-Based Erbium-Doped Fibers for Optical Amplifier: Material and Optical Characterization along with Amplification Properties

Abstract

In this paper, we present phase-separated alumina–silica glass-based Er3+-doped optical fibers made by a modified chemical vapor deposition (MCVD) process in combination with a solution doping (SD) technique. The fibers exhibited better optical performance than other silica-based host glasses—both in terms of spectral broadening and flattening of the gain spectra in the C band (1530–1560 nm) region—as well as an improved lifetime. These phase-separated erbium-doped fibers (EDF) promoted longer Er–O bond lengths and also hexa- and penta-coordinated Al3+ ions instead of the fourfold coordination found in non-phase-separated EDF. It was observed that the higher coordination numbers of Er3+ and Al3+ ions in phase-separated glass hosts led to more homogeneous and inhomogeneous broadening, resulting in better flatness of the gain spectrum with 1.2 dB more gain compared to the non-phase-separated EDF.

Demonstration of laser cooling in a novel all oxide GAYY silica glass

“…A very interesting feature of this particular glass is the phase separation. The majority of commercially available Yb fibres are co-doped with Al because it is an extremely important RE ion solubilizer in silica 10 , 36 , 37 . While phase separation is usually considered as a detrimental to luminescence, the GAYY glasses exhibit the opposite effect.…”

“…5 b. Due to the convective heat load while performing optical cooling experiments at atmospheric pressure, most of the experiments are performed in vacuum 3 , 4 , 6 , 36 . Figure 5 b shows that a maximum temperature reduction of − 6.4 K for a 32.6 W pump power is predicted for GAYY-3 if we conduct the experiments in vacuum, i.e., h cv = 0.…”

“…In this work, we modify the MCVD approach to achieve the production of silica glass preform with high Yb concentration. We increase the rare earth’s solubility by the addition of alumina but promote increased phase separation of the rare earth in the oxide glass 36 , 37 . The fully oxidized active rare-earth ions are immersed in another non-active rare earth to create a local phase separated low phonon energy oxide environment, shielding the rare earth from the detrimental effects of the high phonon energy silica.…”

“…Despite showing promise, the results obtained from these methods have not exceeded those produced by standard vapor deposition technique. Recently, laser cooling has been achieved in silica-based glasses by a number of groups 6,[34][35][36] , with the largest temperature drop reported from room temperature of − 18 K in an alumina rich silica fiber under vacuum using an optimum pump wavelength power of 20 W at 1035 nm 36 . The temperature drop at atmospheric pressure for another fiber was reported to be − 6 K with 185 W of pump power at 1035 nm.…”

Optical polarizability of erbium-oxygen complexes in sol-gel-based silica films

“…In SiO 2 doped solely with 0.073-0.075 mol. % Er 2 O 3 , the Er-O coordination number is 3.75 and bond length is 2.05 Å [38], while for 200 ppm Er, an exceptionally low 1.2coordination with similarly short 2.03 Å bond is measured [20]. Both cited studies report increases in coordination numbers (to 6 or more) and bond lengths (2.32-2.36 Å) for SiO 2 co-doped with Al [38] or Al and Ge [20].…”