Fluoride single crystals for UV/VUV nonlinear optical applications

The growth characteristics and properties of large size SrA1F(5) single crystals are described and compared with those of BaMgF4. Transmission spectra in the vacuum ultraviolet wavelength region indicate a high transparency of SrA1F5 (about 90 % without considering surface reflection loses) down to 150 nm, on contrast to the optical loses observed for BaMgF4. The ferroelectric character of SrA1F(5) is evidenced by the reversal of the spontaneous polarization in a hysteresis loop. The higher potential of SrA1F(5) in comparison with BaMgF4 for the realization of all-solid-state lasers in the ultraviolet wavelength region by the quasi-phase matching (QPM) technique is pointed out. SrA1F(5), besides a higher grade of transparency, shows a nonlinear effective coefficient similar to that of quartz and uniaxial nature, on contrast to the one order smaller nonlinear coefficient and biaxial character of BaMgF4. The refractive index of SrAIF(5) 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 QPM is estimated as a function of the wavelength. The poling periodicity for 193 nm SHG from 386 nm is 4 win.