Growth and investigation of efficient self-frequency-doubling Nd_xGd_1-xCa₄O(BO₃)₃ crystal

In GdCa₄O(BO₃)₃ (GdCOB) crystal, the Gd³⁺ ions can be substituted by Nd³⁺ ions within the concentration of 0-100 at %. Combined laser action of the Nd³⁺ ions and nonlinear optical (NLO) properties of GdCOB crystal host in the mixed Nd_xGd_1-xCOB causes the crystal to become self-frequency-doubling (SFD) material. The synthesis and crystal growth of Nd_xGd_1-xCOB are reported in this paper. The polarized transmittance spectra and fluorescence spectra were measured at room temperature. The strong emission peaks in the range of 850-950 nm are reported for the first time for the Nd_xGd_1-xCOB crystal. The (θ = 66.8°, φ = 132.6°) phase-matching direction was reported for the first time as the optimum phase-matching direction at 1060 nm by calculation and experiments whose d_eff was measured and found to be 2.1 pm/v. The SFD experiments were carried out on 3×3×7 mm³ sample with (66.8°, 132.6°) direction. The green output power at 530.5 nm was 192 mW when pumped by 1600 mW Ti:sapphire tuned to 811 nm. The threshold was 16 mW. The optical-optical conversion efficiency was 12%.