Multimodal emission platform based on Er3+/Yb3+co-doped Ca3Al2Ge3O12 for advanced photonic applications

초록

Er3+/Yb3+ co-doped Ca3Al2Ge3O12 (CAG:Er/Yb) phosphors were synthesized and systematically investigated under dual ultraviolet (UV) and near-infrared (NIR) excitation. X-ray diffraction and Rietveld refinement confirmed that the samples constituted a pure garnet phase with minimal structural distortion. The materials exhibited strong visible and NIR emissions, whose color and intensity depended on the excitation wavelength and Er3+ concentration. Under UV excitation, green emission dominated and showed high-temperature sensitivity, whereas under NIR excitation, red emission increased with Er3+ content, thus affording excitation-dependent color tuning. Temperature-dependent spectra from 293 to 673 K showed that the fluorescence intensity ratio between 2H11/2 and 4S3/2 levels could be used for optical thermometry, with a maximum relative sensitivity of 1.70% K-1 demonstrated at 293 K in the up-conversion mode. The results of Judd-Ofelt (J-O) analysis indicated a moderately asymmetric and rigid local environment that supported balanced visible-NIR emission. The coexistence of dual-excitation green/red contrast and NIR emission suggests the presence of additional channels for anticounterfeiting and optical tagging. These results indicate that CAG:Er/Yb is a stable multifunctional oxide phosphor for temperature sensing and photonic security.

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