Growth, micromechanical aspects, spectroscopy, and laser performance of Yb: CALGO crystal

Yb: CALGO (Yb: CaGdAlO₄) crystal with an 8 at.% Yb doping content was successfully grown, achieving dimensions of 80 mm in length and 30 mm in diameter. Optical, micromechanical traits and laser performance of the crystal have been investigated systematically via various characterization techniques. Due to anisotropic effects, a- and c-directions exhibited distinct micromechanical behaviors. Nanoindentation tests revealed that the a-direction crystal sample primarily exhibits radial cracks, whereas the c-direction one displays non-radial cracks. Both directions were dominated by plastic deformation during loading and unloading. c-direction demonstrated a higher indentation hardness (H_IT = 15.46 GPa) compared to the a-direction one (H_IT = 14.51 GPa), while both directions show similar elastic moduli (E_IT = 312.10 GPa) when using Poisson’s ratio value as 0.25. Absorption and emission cross-sections of the crystal were analyzed, and fluorescence decay time was measured. In lasing action evaluation, pulses as short as 33 fs have been achieved with a spectral bandwidth of 36.7 nm and a peak wavelength of 1061 nm employing a semiconductor saturable absorber mirror as a mode-locker. Such findings provide valuable insights into the mechanical traits and laser performance of Yb: CALGO, specifying its potential for high-performance femtosecond laser applications.