Crystal growth and characterization of titanium-doped near-stoichiometric LiNbO 3

Abstract

Titanium-doped near-stoichiometric LiNbO 3 (SLN) crystals were grown from lithium-rich solutions with a Ti concentration of up to approximately 20 mol% by a top-seeded solution-growth (TSSG) method. Ti-doped SLN (Ti:SLN) crystals with a Ti concentration of up to 9 mol% were free from inclusions, voids, cracks, or mechanical twins. The effective distribution coefficient k eff for Ti in the Ti:SLN crystals was found to be approximately 0.45±0.05 for the Nb atom in the above composition range. The Ti-doping effects on Curie temperature, UV absorption edge, changes in the ordinary and extraordinary refractive indexes (Δ n o and Δ n e), and lattice constants were investigated. The Curie temperature for the Ti:SLN crystals linearly decreased with increasing Ti concentration up to 9 mol%. Both Δ n o and Δ n e linearly increased with increasing Ti concentration up to 9 mol%, and Δ n e was much larger than Δ n o over the entire wavelength range from 440 to 1550 nm. The UV absorption edge for the Ti:SLN crystals shifted to longer wavelengths with increasing Ti concentration. The a- and c-axes lattice constants in the Ti:SLN crystals decreased with increasing Ti concentration. In addition, a photoelastic effect on the refractive-index changes in the Ti:SLN crystal was estimated from the lattice-constant data.