Bifunctional Nd-Doped LGSB Crystals: A Roadmap for Crystal Growth and Improved Laser Emission Performance in the NIR...

Herein we present a roadmap for tailoring the crystal growth conditions, near-infrared (NIR) laser emission, and self-frequency doubling (SFD) performances of newly developed Nd-doped La_xGd_ySc_4-x-y(BO₃)₄ (Nd:LGSB) crystals. Three different Nd³⁺ doping concentrations of 2.3 at.%, 3.5 at.%, and 4.6 at.% were investigated. Considering their incongruent melting, special conditions were employed for the growth using the Czochralski technique. Laser emission performances at 1062 nm in the CW regime were evaluated for uncoated crystal samples with different orientations (a-cut, c-cut, and SFD-cut). The highest slope efficiency η_sa = 0.68 was obtained for the 4.6 at.% c-cut Nd:LGSB crystal, with a randomly polarized emission. The a-cut 4.6 at.% Nd:LGSB crystal delivered a linearly polarized beam with a slope efficiency η_sa = 0.63. The SFD-cut 2.3 at.% and 3.5 at.% Nd:LGSB crystals achieved slightly lower efficiencies of ~ 0.56. The SFD capabilities of 2.3 at.% and 3.5 at.% Nd:LGSB crystals were also explored. Green laser emission at ~531 nm was achieved with a diode-to-green conversion efficiency increasing significantly from 0.17% to 1.44%, respectively. These results demonstrate that the Nd-doping concentration, crystal orientation, and sample length of Nd:LGSB crystals, must be carefully selected depending on the specific requirements of the intended application.