This work presents a detailed investigation of Nd∶YScO₃ mixed sesquioxide crystals, addressing the urgent demand for advanced laser gain materials that combine superior thermal properties and excellent optical performance for high-power laser applications. The study is significant because it addresses the inherent limitations of pure cubic sesquioxides (RE₂O₃), which have excessively high melting point (>2350 ℃) that complicates crystal growth and raises production costs. The innovative approach centers on the YScO₃ system, where the random distribution of Y³⁺ and Sc³⁺ cations creates structural disorder, allowing for considerable spectral broadening, a vital characteristic for ultrashort pulse generation. Since 2020, various rare-earth-doped YScO₃ crystals (including Er, Yb, and Tm) have displayed impressive laser performance, yet the potential of Nd-doped variants for 1 μm applications remained unexplored. This work systematically evaluates Nd∶YScO₃ as a novel gain medium, filling a critical gap in laser material development and providing new opportunities for highly efficient and thermally robust laser systems operating in the technologically important 1 μm spectral region.

The experimental approach utilized the edge-defined film-fed growth (EFG) method to produce 0.5% Nd∶YScO₃ single crystals. This method was chosen for its capacity to ensure precise control over crystal dimensions and doping homogeneity. High-purity (99.99%) oxide powders (Nd₂O₃, Y₂O₃, Sc₂O₃) were accurately weighed according to the stoichiometric formula Nd_0.005Y_0.9975Sc_0.9975O₃, reflecting a nominal 0.5% Nd³⁺ doping concentration (atomic fraction), and thoroughly homogenized through extensive mechanical mixing. Crystal growth occurred in a meticulously controlled argon atmosphere (110 kPa) using a tungsten crucible heated to approximately 2140 ℃ via low-frequency induction, with the pulling rate consistently maintained at 4 mm/h throughout the process. Advanced monitoring systems provided real-time feedback for power adjustments based on weight change rates, ensuring stable growth conditions. Comprehensive characterization included inductively coupled plasma atomic emission spectroscopy for verifying doping concentrations, high-resolution X-ray diffraction for structural analysis, and double-crystal rocking curve measurements for quality assessment. Optical properties were extensively evaluated through absorption and fluorescence spectroscopy. This was followed by a detailed analysis using Judd?Ofelt theory to extract fundamental spectroscopic parameters. Laser performance testing under continuous-wave operation at 1.08 μm validated the material's practical utility.

The Nd∶YScO₃ crystals grown in this study exhibited exceptional quality, as evidenced by sharp, symmetric X-ray diffraction peaks (Fig. 2) and notably narrow rocking curve full-width at half-maximum values (Fig. 3). These findings indicate excellent crystalline perfection with minimal defects. Structural analysis revealed lattice parameters of a=b=c=10.235 ?, which closely followed Vegard’s law between Y₂O₃ and Sc₂O₃. This confirmed the formation of an ideal solid solution with random cation distribution. Spectroscopic characterization demonstrated an absorption cross-section of 0.14×10^-20 cm² at the crucial 808 nm pump wavelength, alongside a particularly strong emission cross-section of 5.1×10^-21 cm² at 1084 nm, positioning it competitively with established Nd-doped laser materials. The fluorescence lifetime of the ⁴F_3/2 energy level was measured at 314 μs, suggesting a high capacity for efficient energy storage. Most significantly, the crystal showcased outstanding laser performance by achieving continuous-wave output at 1.08 μm with a maximum power of 4.03 W and an impressive slope efficiency of 28.4%. This represents the first successful laser operation from Nd∶YScO₃, validating its potential as a practical gain medium. These results significantly advance the field by demonstrating that the YScO₃ host combines the advantages of traditional sesquioxides, such as excellent thermal properties, with the benefits of mixed cation systems (including spectral broadening potential), while maintaining competitive laser performance metrics.

This study established Nd∶YScO₃ as a promising laser gain medium for 1 μm applications through thorough material development and characterization. The EFG method was effective in producing high-quality single crystals, despite the material’s high melting point, and structural analyses confirmed excellent crystalline. The spectroscopic properties, including favorable absorption and emission characteristics combined with efficient energy storage, position Nd∶YScO₃ as a competitive alternative to traditional Nd-doped laser materials. The achievement of efficient continuous-wave lasing at 1.08 μm with a slope efficiency of 28.4% marks a significant milestone in laser material development, particularly for applications requiring high power and thermal stability. The unique structural characteristics of the YScO₃ host, indicated by intermediate lattice parameters and random cation distribution, suggest additional potential for specialized applications needing broad emission spectra or specific thermal management properties. These findings not only broaden the range of available laser gain materials but also offer valuable insights into the fundamental relationships between crystal structure, spectroscopic properties, and laser performance in mixed rare-earth sesquioxide systems. Future research should focus on optimizing doping concentration, exploring different crystal orientations, and investigating the material’s potential for mode-locked operation to fully harness its spectral broadening capabilities. The successful development of Nd∶YScO₃ crystals paves the way for advanced laser systems that combine high efficiency, excellent thermal properties, and unique spectral characteristics.