The near-infrared emission from calcium boroaluminate (CABAL) glasses codoped with Er3+ and Tm3+ has been investigated. It is shown that by controlling the [Tm]/[Er] concentration ratio a fairly flat emission with a bandwidth of 370 nm can be achieved in the wavelength range from 1.4 to 2.0 μm. The broadband emission is formed by three bands centered at 1.4, 1.5 and 1.8 μm, which are related to the emission from the Tm 3+: 3 H 4→3 F 4, Er3+: 4 I 13/2→4 I 15/2 and Tm3+: 3 F 4→ 3 H 6 transitions, respectively. Compared to Er-only doping and Tm-only doping at the same concentration, codoping with both ions leads to a reduction of the intensity and lifetime of the Er-related band at 1.53 μm and to an intensity enhancement of the two Tm-related emission bands at 1.46 and 1.80 μm. This is a result of energy transfer (ET) processes between Er3+ and Tm3+ ions that are relevant when determining the emission spectrum shape. Two dominant ET processes are identified, both consisting of transferring the energy of the Er3+ first excited level (4 I 13/2) in the first case to the Tm3+ first excited level (3 F 4), which is excited to the third excited level (3 H 4), and in the second case to the Tm3+ ground state (3 H 6) which is excited to the first excited level (3 F 4). © 2010 Springer-Verlag.

This work was supported by the Spanish Ministry of Science and Innovation (SB2005-003 and TEC2006-04538), the National Natural Science Foundation of China (Nos. 50602029 and 10604003), Shanghai Municipal Education Commission and Shanghai Science and Technology Commission, Beijing Nova Program (Grant No. 2006B15) from Beijing Municipal Science and Technology Commission, and Program of New Century Excellent Talent in University (NCET-07-0045) of China.

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