Growth and thermal and spectral properties of a new nonlinear optical crystal TmAl3(BO3)4

Single crystals of the nonlinear optical (NLO) material TmAl3(BO3)(4), space group R32, were grown successfully by the top seeded solution growth (TSSG) method for the first time in our laboratory. Morphology analysis reveals that the crystal is a rhombohedron with nine developed faces with the major forms (1210), (2110), and (1120) parallel to the c-axis. Grown crystals were characterized by X-ray powder diffraction (XRD), and second-harmonic generation (SHG) measurements. The two principal coefficients of thermal expansion along (001) and (100) were measured to be 5.33 x 10(-6) and 2.46 x 10(-6) K-1, respectively. In addition, the large difference of thermal expansion coefficients between the two crystallographic axes was discussed based on the structure of this crystal. Polarized absorption spectra were measured, and the results suggest that the optical properties of the TmAl3(BO3)(4) crystal depend greatly on the polarization. This crystal is a promising candidate for NLO materials.