Growth and Characterization of Yb: CALYGLO Crystal for Ultrashort Pulse Laser Applications

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10⁻²⁰ cm² for σ polarization and 5.32 × 10⁻²⁰ cm² for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10⁻²⁰ cm² at 980 nm for σ polarization and 2.28 × 10⁻²⁰ cm² at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at ²F_5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y³⁺ in the crystal is partially replaced by Lu³⁺ and Gd³⁺, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals.