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Abstract: Bi-doped and Yb–Bi-codoped SiO2–Al2O3–CaO glasses were prepared, and the effect of Al2O3 composition on the near-infrared (NIR) emission and energy transfer between Yb3+ and Bin+ (Bi NIR emission centers) were investigated. The introduction of Al2O3 into the glass hosts can vary the NIR luminescence centered at 1300nm and obtain the strongest emission when the concentration of Al2O3 is 15mol%. Efficient energy transfer from Yb3+ to Bin+ is achieved by co-doping of Al2O3. With the increased Al2O3 concentration, the energy transfer efficiency between Yb3+ and Bin+ increased at first and then decreased, maximizing (~79%) at 8mol%. It is suggested that the introduction of appropriate Al2O3 concentration in Yb–Bi-codoped silicate glasses may be an efficient way to realize effective optical amplification with commercially available 976nm LD pumping. [Copyright &y& Elsevier]

Abstract: We have studied the effects of Si doping on the near infrared (NIR) luminescence observed in low Bi doped ( 0.1mol% ) glasses and the energy transfer from Yb3+ to Bi. The broadband near infrared can only be observed when Si is introduced in the Bi-doped glass. The origin of this fluorescence can be attributed to Bi ions at low valence. Efficient energy transfer from Yb3+ to Bi NIR active ions is achieved by co-doping of Si. There is an increment of about ~29 times of the emission intensity from Bi-related active center as the Yb3+ concentration varies from 0 to 2.0mol% and the amount of Si is 0.05mol% under 980nm excitation. The possible mechanism of energy transfer from Yb3+ to Bi is also discussed. [Copyright &y& Elsevier]