Single crystal structure and optical properties of nonlinear optical crystal Rb0.94Ti0.94Ta0.06OPO4

Rb0.94Ti0.94Ta0.06OPO4 (RTP:Ta) single crystal was grown by the top seeded solution growth method. The good crystalline quality of the as-grown crystal was confirmed by the X-ray rocking curve analysis. The chemical composition was analyzed by performing electron probe microanalysis (EPMA) and inductively coupled plasma optical emission spectrometry (ICP-OES). Detailed structural investigations were performed through the Single-Crystal X-ray diffraction technique. The cell parameters of Rb0.94Ti0.94Ta0.06OPO4 are a = 12.9604(2) A, b = 6.4988(9) A, c = 10.5705(2) A and V = 890.3(2) A3. It is shown that Ta5+ ions replace Ti4+ ions in the structure, and the electroneutrality of the crystal is stabilized by creating Rb+ vacancies. Ta cations occupy both Ti(1) and Ti(2) sites; the occupancies of Ta cations in Ti(1) sites and Ti(2) sites are 0.077(4) and 0.048(4), respectively. The Rb vacancy rate is 0.062(1) and more Rb vacancies are found at Rb(2) sites. It is shown that the occupancies of Ta and Rb cations correlate with the bond lengths of Ti–Rb and Rb–O. Rb0.94Ti0.94Ta0.06OPO4 single crystal exhibits high transmittance up to 85% in the range of 0.35 to 4.5 μm. The UV cutoff wavelength of Rb0.94Ti0.94Ta0.06OPO4 shows a 6 nm red-shift compared to that of RTP. At the wavelength of 1064 nm, the absorption coefficients for Rb0.94Ti0.94Ta0.06OPO4 crystal along a, b and c-directions are 0.19 cm−1, 0.15 cm−1 and 0.06 cm−1, respectively. The second harmonic generation (SHG) efficiency of Rb0.94Ti0.94Ta0.06OPO4 is about 1.4 times that of RTP. The relationship between the crystal structure and the nonlinear optical property of Rb0.94Ti0.94Ta0.06OPO4 is discussed in detail. The distorted TiO6 octahedra and typical short Ti–O bonds endow this crystal with SHG efficiency comparable to that of RTP. Our results indicate that Rb0.94Ti0.94Ta0.06OPO4 crystal is an excellent nonlinear optical material for potential applications.