Orientational dependences of optical properties in BaMgF4

Abstract In this research, crystal orientation dependences of optical properties have been investigated for magnesium barium fluoride (BaMgF4) in three-dimensional space by means of coordinate transformations. The maximum nonlinear optical coefficients dij' and refraction indices nij' along specific orientations have been determined based on experimental data of BaMgF4 and original matrices for mm2 point group. All the nonlinear optical coefficients dij' show high dependence on crystal orientations compared with refraction indices nij', the latter can be treated as a constant (1.45 ± 0.02), which is both related to experimental data and crystal symmetry elements. The max d15' = 15 × 10−14 m/V and the max d31' = max d32' = 27 × 10−14 m/V can be both obtained along the spontaneous polarization axis, i.e., the Z-axis. Meanwhile, the max d24' = 26.7 × 10−14 m/V and the max d33' = 36 × 10−14 m/V lie along directions at angles of θ = 58° and 50.2° apart from the Z-axis, respectively. The result suggests that by adopting specific directions, the optical properties of BaMgF4 crystal can be optimally used.