Optical and thermal properties of nonlinear optical crystal LaCa4O(BO3)3

The nonlinear optical (NLO) crystal LaCa4O(BO3)3 (LaCOB), with a large size and a good optical quality, has been grown from the melt by the Czochralski pulling method. The structure of LaCOB belongs to the monoclinic system with space group Cm, the unit cell constants are a=0.8168(3), b=1.6081(7), c=0.3630(6) nm, and β=101.38(9)°. The crystal possesses a wide transmission range from UV to IR, which is advantageous for applications as a NLO material. The orientation relationship between the crystallographic axes and the optical indicatrix axes was determined and the refractive indices were measured. The specific heat of the crystal is 308.3 J/mol K at 300 K. The three principal coefficients of thermal expansion are 5.61×10−6, 7.21×10−6, and 11.01×10−6 K−1, respectively.