Refractive-Index Changes of Titanium-Doped Near-Stoichiometric LiNbO3 Crystals

概要

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Titanium-doped (up to 9 mol%) near-stoichiometric LiNbO3 (SLN) crystals were grown from lithium-rich solutions by the top-seeded solution-growth method. The ordinary and the extraordinary refractive indices ($n_{\text{o}}$ and $n_{\text{e}}$) of the titanium-doped SLN (Ti:SLN) crystals were measured at room temperature by the prism-coupling technique in the wavelength range from 440 to 1550 nm. The relations between titanium concentrations and the ordinary and the extraordinary refractive-index changes ($\Delta n_{\text{o}}$ and $\Delta n_{\text{e}}$) of the Ti:SLN crystals were investigated. Accordingly, it was found that both $\Delta n_{\text{o}}$ and $\Delta n_{\text{e}}$ linearly increase with increasing titanium concentration up to 9 mol% and that $\Delta n_{\text{e}}$ is much larger than $\Delta n_{\text{o}}$ over the whole wavelength range. It was also found that both $\Delta n_{\text{o}}$ and $\Delta n_{\text{e}}$ increase with decreasing wavelength in all the Ti:SLN crystals with different titanium concentrations. Moreover, $\Delta n_{\text{e}}$ of Ti:SLN doped with approximately 4 mol% of titanium (approximately $1\times 10^{-2}$) is almost the same as that of titanium-diffused SLN waveguides. In addition, a photoelastic effect on the refractive-index changes in the Ti:SLN crystal was estimated from using lattice-constant data determined by X-ray diffraction.
Japan Society of Applied Physicsの論文
2003-10-01