Realization of modulating broadband emission from Er–Tm codoped calcium boroaluminate glasses by dual-wavelength pumping

Near-infrared photoluminescence (PL) of calcium boroaluminate (CABAL) glasses codoped with Er2O3 and Tm2O3 has been investigated by dual-wavelength pumping at 795 and 476 nm. Spectrum shape of broadband emission could be modulated by controlling the power ratio of two pumping lines (P476/P795). The result shows that the full width at half maximum can reach ∼500 nm in the wavelength range from 1.3 to 2.0 μm by controlling P476/P795 = 12. The PL spectra show four characteristic peaks located at 1.46, 1.53, 1.58 and 1.80 μm, corresponding to Tm3+: 3H4 → 3F4, Er3+: 4I13/2 → 4I15/2, Tm3+: 1G4 → 3F2 and Tm3+: 3F4 → 3H6 emissions, respectively. The energy transfer (ET) (ET1: Er3+: 4I13/2, Tm3+: 3F4 → Er3+: 4I15/2, Tm3+: 3H4 and ET2: Er3+: 4I13/2, Tm3+: 3H6 → Er3+: 4I15/2, Tm3+: 3F4) between Er3+ and Tm3+ ions play important roles in the luminescence mechanisms. In addition, a new ET process (ET: Tm3+: 1G4, Er3+: 4F9/2 → Tm3+: 3F2, Er3+: 4F7/2) was identified. The flat broadband emission with the bandwidth of ∼500 nm could be realized by changing P476/P795 as a result of the radiative transitions, Tm–Tm cross-relaxation (Tm3+: 3H4, 3H6 → Tm3+: 3F4, 3F4) and Er–Tm ET processes.