关键词: 氟化钡晶体, 钬离子掺杂, 中红外激光, 光谱性能

Abstract: Infrared lasers in the 1-3 μm region are increasingly important for applications in medical treatment, atmospheric monitoring, and high-power laser systems. Holmium ions (Ho³⁺) are particularly attractive because of their multiple emission channels covering near to mid infrared ranges. This work aims to systematically evaluate the structural and spectroscopic properties of Ho:BaF₂ crystals and determine the optimal doping concentrations for efficient multi-band laser operation. High-quality Ho:BaF₂ single crystals with concentrations of 0.5%-3.0% (in atomic) were grown using the temperature gradient technique (TGT). Structural characterization was performed by XRD and ICP-AES, while spectroscopic properties were analyzed via absorption, fluorescence, and lifetime measurements. Judd-Ofelt analysis was further applied to calculate radiative parameters. All samples exhibited pure cubic fluorite structures, with doping segregation ratios close to unity and uniform Ho³⁺ distribution. Spectroscopic evaluation revealed optimal doping concentrations of 2.0% (in atomic) for ~1.2 μm (⁵I₆→⁵I₈, Q=24.29×10⁻²¹ cm²·ms) and ~2.05 μm (⁵I₇→⁵I₈, Q=67.53×10⁻²¹ cm²·ms), and 1.0% (in atomic) for ~2.85 μm (⁵I₆→⁵I₇, Q=44.52×10⁻²¹ cm²·ms). The BaF₂ host, with its low phonon energy (~346 cm⁻¹) and anti-clustering characteristics, enabled enhanced emission performance, including a maximum emission cross-section of 3.81×10⁻²¹ cm² at ~2.05 μm. These results outperform traditional hosts such as YAG and CaF₂. Compared to oxide hosts, BaF₂ offers superior lifetime, reduced non-radiative losses, and greater resistance to concentration quenching. The findings indicate that Ho:BaF₂ supports higher effective doping levels, making it particularly promising for high-power and ultrafast laser applications. Ho:BaF₂ crystals demonstrate excellent potential as efficient, multi-wavelength infrared laser gain media.

Key words: BaF₂ crystals, holmium doping, mid-infrared lasers, spectroscopic characteristics