(a) XRD patterns of samples doped with various concentrations ofYb. (b) Enlarged details of diffraction peaks from 26.3 to 27.3 degree. (c)Reference JCPDS card of the CaCuSi4O10 crystals. Trace amount of NaCl was detected in some samples.
Diffuse reflection spectra of the CCS00 and CCS10 samples. Inset shows an enlarged part in NIR region. A break point at 923 nm (grey circle) was introduced by detector change during the measurements (from InGaAs to PMT detectors).
PL spectra of samples doped with various concentrations of Yb under excitation of 540 nm at RT.
PLE spectra of the CCS00 (monitoring wavelength: 870 nm) and CCS10 samples (870, 1000, 1025 nm, respectively). The PLE spectra of CCS (870 nm) was fitted by Gaussian functions.
Decay curves of 870 nm (a) and 1007 nm (b) emission in various samples under excitation of 540 nm.
Population and depopulation processes of Cu2+ and Yb3+ ions in the excited states. (a) The moment after 540 nm pulsed excitation by a flash lamp. (b) Beginning stage of decay with dominant forward energy transfer (FET: Cu2+→Yb3+). (c) Balanced stage of decay with parallel FET and back energy transfer (BET: Yb3+→Cu2+). NCu 2, NCu 1, NYb 2, NYb 1 are the numbers of Cu2+ and Yb3+ ions in excited states and ground states, respectively. AR , WMP , WFET , and A′R , W′NR , WBET refer to radiative emission, non-radiative relaxation, energy transfer in Cu2+ and Yb3+, respectively.
(a) PL spectra of the CCS10 sample under 540 nm excitation at various temperatures. The inset shows an enlarged view of the blue frame. (b) Integrating intensity of Cu2+, Yb3+ and total emission as a function of temperature.
Normalized shape functions of Cu2+ emission, Yb3+ absorption, as well as Yb3+ emission, Cu2+ absorption cross-sections, which are calculated from the PL and absorption spectra of the CCS10 sample at RT.
Nominal compositions of the samples (in mole ratio).
Calculated crystal parameters of the CaCuSi4O10 phase in the CCS00 to CCS10 samples.
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