Er-Yb co-doped silica fiber (EYDF) has wide application in free-space telecommunications, remote sensing, and range finding. However, the parasitic laser around 1μm of Yb³⁺ ions seriously restricts the applications of EYDF. In order to solve this problem, high concentrations of phosphorus are always doped into silica matrix. However, single-doping with large amounts of phosphorus shows a detrimental central dip in the refractive index profile, a high core numerical aperture (NA) and a high core background loss.

In a recent study, a team from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made new progress on the structure-property relations of EYDF core glass. Related work was published on Optical Materials Express.

In their experiment, Er/Yb/Al/P-doped silica (simplified as EYAPS) glasses with different P/Al ratios were fabricated. The effect of P/Al ratio on the spectroscopic properties of Er³⁺ ions and their local environment as well as the global glass network structure were studied systematically.

With the increase of P/Al ratio, they found that rare earth ions gradually moved from silicon rich and aluminum rich environment to phosphorus rich environment. And the maximum phonon energy of EYAPS samples gradually increased from 1200 to 1326 cm^-1 due to the formation of AlPO₄-like unit and P=O double bonds.

These structural changes lead to gradual increase of peak absorption and emission cross sections of Er³⁺ ions at 1.5 μm as well as the energy transfer efficiency from Yb³⁺ to Er³⁺ ions.

This work demonstrates that the local environment and spectral properties of Er³⁺ ions in Er/Yb/Al/P co-doped silica glass with P/Al ratio more than one is similar to that of Er/Yb/P co-doped silica glass. The common disadvantages in Er/Yb/P co-doped fibers may be solved by an optimized Er/Yb/Al/P co-doping composition.

The research was supported by National Natural Science Foundation of China (NSFC).

Effect of P/Al ratio on the structure and properties of EYAPS samples. (Image by SIOM)

Article website:
https://doi.org/10.1364/OME.389769

Contact:
Mr. CAO Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS
Email: caoyong@siom.ac.cn