REFRACTIVE-INDEX STUDIES IN CA2GA2SIO7 AND SRLAGA3O7 MELILITE-TYPE COMPOUNDS

Refractive-index dispersion and anisotropy were measured in tetragonal Ca2Ga2SiO7 (CGSM; Ga-gehlenite) and SrLaGa3O7 (SLGM) single crystals at room temperature between 308 and 1064 nm. Large single crystals wer e grown by the Czochralski method. Bireflectance in a crystallographic ally oriented single-crystal prism was used for an accurate measuremen t of the anisotropy. CGSM is negative uniaxial. At the wavelength lamb da = 632.8 nm the ordinary and the extraordinary refractive indices n( o) and n(e) were n(o) = 1.7214 +/- 0.0004 and n(e) = n(o) - 0.0112 +/- 0.0001. The temperature dependence was dn(o)/dT = (12.7 +/- 0.2) x 10 (-6)degrees C-1 and dn(e)/dT = (5.4 +/- 0.4) x 10(-6)degrees C-1. SLGM is positive uniaxial. At lambda = 632.8 nm, n(o) = 1.8249 +/- 0.0004 and n(e) = n(o) + 0.0097 +/- 0.0001. The temperature dependence was dn (o)/dT = (15.3 +/- 0.2) x 10(-6)degrees C-1 and dn(e)/dT = (10.5 +/- 0 .5) x 10(-6)degrees C-1. The refractive-index dispersions were fitted to a Sellmeier function. Both materials can be considered for use in n onlinear optics (frequency doubling, optical parametric oscillations). (C) 1996 Optical Society of America.