Refractive index of SrAlF5 and derived grating period for UV/VUV quasi-phase-matching SHG

SrAlF5 has recently become one of the most promising candidates for the realization of all-solid-state lasers in the ultraviolet wavelength region by the quasi-phase-matching technique. It has been shown that it is highly transparent down to the cutoff wavelength at about 150 nm, optically uniaxial and ferroelectric. The refractive index of SrAlF5 from the ultraviolet to the near-infrared wavelength region is measured by the minimum deviation method. The Sellmeier and Cauchy coefficients are obtained from the fits to the curves of the ordinary and extraordinary refractive indices, and the grating period for the first-order quasi-phase-matching is estimated as a function of the wavelength. The effective nonlinear coefficient is similar to that of quartz, deff≈0.3-0.4 pm/V, and the poling periodicity for 193 nm SHG from 386 nm is 4.1μm.