Linear and nonlinear optical properties of Na3La2(BO3)3 crystal

Abstract

A 30×20×8 mm 3 Na 3 La 2 (BO 3 ) 3 crystal has been grown by the top-seeded solution growth method (TSSG) using Na 2 O–B 2 O 3 –NaF as flux. The refractive indices at thirteen wavelengths from 0.2537 to 2.325 μm were accurately measured by the minimum deviation method, and the Sellmeier equations were accordingly constructed. The nonlinear optical (NLO) coefficients were measured by the Maker fringe method, which gave results of d 31 =1.45 pm/V, d 32 =0.67 pm/V, and d 33 =−1.06 pm/V, respectively. For second-harmonic generation (SHG) of 1064 nm, the effective NLO coefficient ( d eff ) of type I phase-matching reaches the maximum value (1.44 pm/V) at the phase-matching angles θ =77.0°, ϕ =212.1°, which is larger than that of LiB 3 O 5 (LBO). First-principle calculations suggest that Na 3 La 2 (BO 3 ) 3 possesses two types of NLO-active atom groups, BO 3 group with π-orbital system and La-centered polyhedron with large polar displacement, of which the latter could be considered as a new type of NLO-active atom group. • The refrative index and NLO coefficient have been measured for the first time. • The maxium effective NLO coefficient is larger than that of LBO crystal. • The distorted rare earth cation-centered polyhedron is suggested as new NLO-active atom group.