Role of Dy 3+ ion clusters in CaF 2 : Dy 3+ crystals on yellow and mid-infrared laser characteristics

Abstract

CaF2 single crystals doped with Dy3+ in different concentrations (1–8 at.%) were grown by the Bridgman method. Their structural and spectral features were studied to realize the concentration quenching mechanisms of yellow (~570 nm) and mid-infrared (~3 μm) emissions. XRD and Raman analyses confirmed that all crystals retained the fluorite structure. At high doping concentrations, charge compensation and cluster formation led to lattice expansion and increased disorder. In absorption spectra, the peak positions, absorption cross-sections, and full widths at half maximum did not change with doping concentration. The yellow emission exhibited complex concentration-dependent behavior, confirming the existence of at least two types of Dy3+ clusters (L-type and M/ N-type) with different fluorescence lifetimes in CaF2, which showed distinctly different yellow luminescence characteristics. In contrast, the mid-infrared emission at 2901 nm is less affected by cluster type, achieving optimal performance at a doping concentration of 6 at. %, with a stable emission cross-section of approximately 3.1 × 10-21 cm2. This work provides a systematic understanding of the structure-property relationships in Dy3+: CaF2 crystals and offers a route for the development of dual-band yellow and mid-infrared laser materials.