2 μm emission properties and nonresonant energy transfer of Er3+ and Ho3+ codoped silicate glasses

2.0 mu m emission properties of Er3+/Ho3+ codoped silicate glasses were investigated pumped by 980 nm LD. Absorption spectra were determined. Intense mid-infrared emissions near 2 mu m are observed. The spectral components of the 2 mu m fluorescence band were analyzed and an equivalent model of four-level system was proposed to describe broadband 2 mu m emission. Low OH- absorption coefficient (0.23 cm(-1)), high fluorescence lifetime (2.95 ms) and large emission cross section (5.61 x 10(-21) cm(2)) corresponding to Ho3+: I-5(7)-> I-5(8) transition were obtained from the prepared glass. Additionally, energy transfer efficiency from the Er3+: I-4(13/2) to the Ho-3+:I-5(7) level can reach as high as 85.9% at 0.75 mol% Ho2O3 doping concentration. Energy transfer microscopic parameters (C-DA) via the host-assisted spectral overlap function were also calculated to elucidate the observed 2 mu m emissions in detail. Moreover, the rate equation model between Er3+ and Ho3+ ions was developed to elucidate 2 mu m fluorescence behaviors with the change of Ho3+ concentration. All results reveal that Er3+/Ho3+ codoped silicate glass is a promising material for improving the Ho3+ 2.0 mu m fiber laser performance.