STED properties of Ce³⁺, Tb³⁺, and Eu³⁺ doped inorganic scintillators

Scintillator-based X-ray imaging is a powerful technique for noninvasive real-space microscopic structural investigation such as synchrotron-based computed tomography. The resolution of an optical image formed by scintillation emission is fundamentally diffraction limited. To overcome this limit, stimulated scintillation emission depletion (SSED) X-ray imaging, based on stimulated emission depletion (STED) microscopy, has been recently developed. This technique imposes new requirements on the scintillator material: efficient de-excitation by the STED-laser and negligible STED-laser excited luminescence. In this work, luminescence depletion was measured in several commonly-used Ce³⁺, Tb³⁺, and Eu³⁺ - doped scintillators using various STED lasers. The depletion of Tb³⁺ and Eu³⁺ via 4f-4f transitions was more efficient (P_s = 8…19 mW) than Ce³⁺ depletion via 5d-4f transitions (P_s = 43…45 mW). Main origins of STED-laser excited luminescence were one- and two-photon excitation, and scintillator impurities. LSO:Tb scintillator and a 628 nm cw STED-laser is the most promising combination for SSED satisfying the above-mentioned requirements.