Potential of Yb-doped CALYSO single crystal fiber as a laser medium for ultrashort laser operation

For the first time, single crystal fibers of 2 at.% Yb:CaYAlO₄ (Yb:CALYO) and Yb:CaY_0.95Sc_0.05AlO₄ (Yb:CALYSO) were successfully grown using the LHPG method. The structure, absorption, emission, and lifetime characteristics of Yb:CALYO and Yb:CALYSO single crystal fibers were systematically investigated. Additionally, the influence of Yb³⁺ concentration on these properties was examined. The absorption cross-sections of Yb:CALY(S)O single crystal fibers were calculated, revealing that the strongest absorption peaks are located at 979 nm. The emission cross-sections for 2 at.% Yb:CALYO and Yb:CALYSO crystal fibers were determined to be 0.88 × 10⁻²⁰ cm² at 982 nm and 0.81 × 10⁻²⁰ cm² at 983 nm, with full widths at half maximum (FWHM) of 85.37 nm and 88.34 nm, respectively, corresponding to the transition of ²F_5/2 → ²F_7/2. The fluorescence lifetimes of the ²F_5/2 energy level for Yb:CALY(S)O crystal fibers with a concentration of 2 at.% were calculated to be 706 μs and 682 μs, respectively. The experimental results indicate that Yb:CALYSO crystal fiber holds potential as a laser medium for ultrashort laser operation.