A new oxyborate crystal, GdCa4O(BO3)(3): Defects and optical properties

Large size and high quality doped and undoped GdCOB crystals were grown usi ng Czochralski pulling method from Pt crucible under air atmosphere. The de fects were observed using microscopy combined with chemical etching method. The cause of the twins, inclusions and dislocation defects in GdCOB crysta l were discussed, The optimum phase-matching direction is out of the main p lane, which is along (theta = 66.8,phi = 132.6). The intracavity second-har monic-generation (SHG) conversion efficiency of 12mm long GdCOB cut along t his optimum PM direction is 25%, 1.22W continuous-wavelength green laser wa s obtained at IOW LD power. When GdCOB crystal is doped by Sr2+, Bi3+, Li+, Yb3+ and Tm3+ cations, the SHG conversion efficiencies are improved obviou sly because the cations make the anion groups in GdCOB crystal more distort ed. Gd0.37Y0.63COB crystal can realize non-critical PM third-harmonic-gener ation (THG) at room temperature. The THG properties of beta -BBO and Gd0.37 Y0.63COB crystals are compared. The self-frequency-doubling (SFD) propertie s of NdGdCOB crystal were studied. The SFD optical-optical conversion effic iency of NdGdCOB crystal is 14.4% when pumped by Ti:sapphire laser while it is 7.7% when pumped by dye-laser. The passive Q-switched and modulated Q-s witched phenomena were analyzed. The power density of the passive Q-switch pulse was 16.5MW/cm(2). When gadolinium ion was substituted by Dy3+ ion, th e Dy:GdCOB crystal will emit yellow fluorescent at 585nm. Yb3+ ion has sens itizing effect on other rare-earth ions in GdCOB crystal. The upconversion mechanisms in co-doped GdCOB crystal were discussed.