Search

Abstract: Secondary ion mass spectrometry (SIMS) was used to study the diffusion properties of Mg2+ and Ti4+ ions in a peculiar optical-damage-resistant near-stoichiometric (NS) Ti:Mg:LiNbO3 waveguide structure that a number of strip waveguides are embedded in a planar waveguide. The structure was fabricated on an initially congruent, undoped Z-cut substrate with a technological process in sequence of planar waveguide, strip waveguide, MgO diffusion and post Li-rich vapor transport equilibration (VTE) treatment. The results show that the Mg2+-profiles in both strip and planar waveguide layers are desirably homogeneous with a concentration 1.7±0.3mol% above the optical damage concentration threshold. The Ti4+-profile in the strip waveguide follows a sum of two error functions along the lateral direction with a width 13±1.0μm and a sum of two Gaussian functions in the depth direction with a 1/e depth of ∼11μm all. The Ti4+ ions in the planar waveguide obey a Gaussian profile. From the measured profiles, characteristic diffusion parameters such as mean Mg2+ and Ti4+ diffusivities and surface Ti4+-concentration are evaluated. The diffusivity is discussed in comparison with the previously reported results on single Mg2+, Ti4+ diffusion and Mg2+/Ti4+ co-diffusion in pure (or bulk MgO-doped), congruent (or NS) LiNbO3 crystal. Finally, the keys to the succeeding in fabrication are highlighted. [Copyright &y& Elsevier]

Abstract Gallium-diffused lithium niobate (LiNbO 3) channel optical thin-film was fabricated by diffusion of photolithographically patterned gallium-oxide stripes on a Z-cut congruent LiNbO 3 substrate. Composition, optical properties of the channel thin-film and gallium diffusion profiles were characterized. The results show that the thin-film is in congruent composition environment, confines single-mode ordinary and extraordinary waves with a loss <0.5 dB/cm at 1.5 μm wavelength. The confined mode field follows Gaussian/Hermite-Gaussian profile in the width/depth direction of the channel thin-film, and shows definite anisotropy. The diffused gallium ions follow a sum of two error functions in the width and a Gaussian function in the depth direction of the channel optical thin-film. Two-dimensional gallium concentration and refractive index profiles in the channel thin-film are modeled. [ABSTRACT FROM AUTHOR]

Ti-diffused LiTaO 3 strip waveguide was fabricated by in-diffusion of 8-μm-wide, 100-nm-thick Ti-strip at 1300 °C for 6 h in wet O 2 atmosphere. Its composition, surface morphology, lattice parameter, optical properties and Ti profile characteristics were fully characterized. It is shown that the waveguide is in the congruent composition environment. The waveguide surface caves in ∼70 nm below the crystal surface due to Ti-induced lattice contraction, which is verified by X-ray single-crystal diffraction. Optical characterizations show that the waveguide well supports both TE and TM single-mode propagation at the 1.5 μm wavelength, is polarization-insensitive, and has a loss of 0.4 (0.3) dB/cm for the TM (TE) mode. Secondary ion mass spectrometry analysis shows that the Ti profile follows a sum of two error functions in the width direction and a Gaussian function in the depth direction of the waveguide. [ABSTRACT FROM AUTHOR]

Abstract: Diffusivity of Li+ in 5mol% (in growth melt) MgO-doped LiNbO3 crystal has been studied as a function of Li2O-content ranging from 43.4 to 44.4mol% under different temperatures. First, diffusion-limited Li2O-content depth profiles were produced by carrying out Li-poor vapour transport equilibration (VTE) treatments on two 0.5-mm-thick MgO-doped LiNbO3 plates at 1100 and 1130°C for 40h. Second, the profiles were obtained by alternatively doing the optical polish to one crystal surface and the Li2O-content characterization on the polished surface through the measurement of birefringence. Third, Boltzmann–Matano method was applied to the profile to derive the Li+ diffusivity as a function of Li2O-content. The results show that the diffusivity decreases with the reduced Li2O-content by at least two orders of magnitude as the Li2O-content reduces by 1mol% from the as-grown state. In the Li2O-content range studied, the diffusivity at 1130°C is at least two times larger than that at 1100°C. In addition, we also studied the time dependence of the Li-poor-VTE-induced reduction of Li2O-content on surface of the same MgO-doped crystal. The results show that the surface Li2O-content reduction induced has a square-root dependence on the VTE duration. Based upon this dependence, the mathematical solution to the Li+ diffusion equation, an integral of error function complement, is obtained and verified by the experimental result. It is concluded that the MgO doping has less effect on both the Li+ diffusivity and the dependence of surface Li2O-content reduction on the VTE duration. [Copyright &y& Elsevier]