Homogeneity and SHG properties of K₃Li_2-xNb_5+xO_15+2x single crystals grown by micro-pulling-down technique

Homogeneity of potassium lithium niobate single-crystal fibers grown by micro-pulling-down technique is examined via second-harmonic-generation measurement both in axial and radial directions. It is found that fluctuation of phase-matching wavelength along the growth axis is small and independent of growth rate. On the other hand, relatively large variation of phase-matching wavelength is found along the radial direction. The phase-matching wavelength shows its minimum around the center of the section of the fiber and increase toward the periphery. Compositional inhomogeneity and internal strain in the radial direction are investigated in association with variation of phase-matching wavelength. X-ray rocking-curve analysis, absorption measurement and polarized beam transmittance are also reported.