Temperature dependence of the spectral properties of Yb 3+ /P 5+ /Al 3+ co-doped silica fiber core glasses

Abstract

Yb 3+ /P 5+ /Al 3+ co-doped silica fiber core glasses with different P 5+ /Al 3+ molar ratios were prepared by the sol-gel method and modified chemical vapor deposition (MCVD) method. The absorption and fluorescence spectra were measured using a temperature range from 25°C to 200°C. Results show that both the major absorption and emission peaks of the Yb 3+ ions become weaker and wider with the temperature increasing. The absorption cross sections of HYPA1 (the molar compositions of 0.2Yb 2 O 3 -2P 2 O 5 -2Al 2 O 3 -95.8SiO 2 ) preform slices made by MCVD with a composition similar to the commercial 20/400 ytterbium-doped silica fibers (YDFs) decrease by ∼31.8% (915 nm), ∼25.3% (940 nm) and ∼41.6% (975 nm), in addition, the emission cross sections decrease by ∼32.1% (1030 nm) and ∼22.7% (1080 nm), respectively, all which indicate the decline of the laser properties with the temperature increasing of Yb 3+ doped glass samples. The highest absorption peak at 975 nm of HYPA1 is blue-shifted by 0.80 nm as temperature raised from 25°C to 200°C and the absorption coefficient of the peak wavelength is reduced by nearly 5%. Additionally, the results also demonstrate that the R abs (the ratio of σ abs@975 nm /σ abs@915 nm ) and R em (the ratio of σ em@1030 nm /σ em@1080 nm ) are affected not only by the P 5+ /Al 3+ molar ratio but also by the temperature. This work is helpful for understanding the fiber laser performance variations with the increase of the fiber core temperature due to high power operation.