Wan-Ying Du

Electro-optic property of Ti 4+ -doped LiNbO 3 single crystal

Electro-optic property of Ti4+-doped LiNbO3 single crystal is investigated. The electro-optic coefficients γ33 and γ13 of a series of bulk Ti4+-doped congruent LiNbO3 crystals with different Ti4+ concentrations up to 12 mol% in crystal were measured by Mach-Zehnder interferometric method and correlated with the Ti4+-doping concentration. Both clamped and unclamped coefficients were measured. The results show that both γ33 and γ13 reveal a degradation tendency with the increase of Ti4+ concentration in both cases of clamped and unclamped measurements. Nevertheless, the degradation is no more than 15% for the considered Ti4+ concentration up to 12 mol%. The little effect is explained qualitatively and comprehensibly.

Note: Electro-optic coefficients of Li-deficient MgO-doped LiNbO3 crystal

A number of Li-deficient MgO-doped LiNbO3 (LN) crystals with different Li2O contents ranging from 43.4 mol. % to 44.5 mol. % were prepared by carrying out the Li-poor vapor transport equilibration treatment on 5 mol. % (in growth melt) MgO-doped LN crystals. Unclamped electro-optic (EO) coefficients γ13 and γ33 of these crystals were measured by Mach-Zehnder interferometry. The results show that γ13 (γ33) increases linearly by ∼14% (11%) as the Li2O content decreases from 44.5 mol. % of the as-grown state to 43.4 mol. % of the Li-deficient state. This feature is desired for the EO application of the Li-deficient MgO:LN crystal.

Electro-Optic Property of Er 3+ -Doped LiNbO 3 Single Crystal for Integrated Optics

Er³⁺-doping effect on electro-optic property of LiNbO₃ crystal has been studied. A series of congruent LiNbO₃ crystals homogenously doped with different Er³⁺ concentrations up to 2 mol% in melt were grown. Unclamped electro-optic coefficients r₁₃ and r₃₃ of these crystals were measured by Mach-Zehnder interferometry. The results show that both r₁₃ and r₃₃ reveal little dependence on Er³⁺ doping level. r₁₃ hardly changes in the studied Er³⁺ doping level range 0-2 mol% within the experimental error of 3%. r₃₃ reveals a degradation tendency with a rise in the Er³⁺ doping level, but the degradation is no more than 5% in the Er³⁺ doping level range studied. The small effect is consistent with previous result that the performance of an electro-optic device based on Ti⁴⁺-diffused Er³⁺-doped LiNbO₃ waveguide is not influenced noticeably by Er³⁺-doping. A qualitative, comprehensible explanation is given for the small effect.

Zirconium-diffusion-doped Ti:LiNbO3 strip waveguide for integrated optics

We report Zr4+-doped Ti:LiNbO3 strip waveguide fabricated by Zr4+-diffusion-doping followed by diffusion of 8 μm wide, 100 nm thick Ti-strips on a Z-cut congruent substrate. Optical study shows that the waveguide well supports both TE and TM, is single-mode at the 1.5 μm wavelength, and has a loss ≤ 1.3/1.5 dB/cm for the TE/TM mode. Secondary ion mass spectrometry study shows that the Zr4+-profile part having a Zr4+-concentration above the threshold of photorefractive damage covers 60% (70%) ordinary (extraordinary) index profile in the waveguide. We conclude that the waveguide is optical-damage-resistant.

Near-stoichiometric Ti:Sc:LiNbO 3 strip waveguide for integrated optics

We demonstrate near-stoichiometric Ti:Sc:LiNbO3 strip waveguide fabrication starting from a congruent LiNbO3 substrate with a technological process in sequence of Sc3+-diffusion-doping, Ti diffusion, and post Li-rich vapor transport equilibration. We show that the waveguide is in a near-stoichiometric composition environment, well supports single-mode propagation at 1.5 μm wavelength under both TE and TM polarizations, shows considerable polarization dependence, and has a loss ≤ 0.4/0.7 dB/cm for TE/TM mode. The Ti4+ surface profile can be fitted by a sum of two error functions, the depth profile can be fitted by a Gaussian function, and the Sc3+-profile part which has a concentration above the threshold of photorefractive damage entirely covers the waveguide, showing that the waveguide is expected to be optical-damage-resistant.

Polarization-insensitive, shallow Ti-diffused near-stoichiometric LiTaO 3 strip waveguide for integrated optics

We report on a Ti-diffused near-stoichiometric (NS) LiTaO3 strip waveguide fabricated by diffusion of an 8 μm wide, 160 nm thick Ti-strip followed by Li-rich vapor transport equilibration. It is found that the waveguide surface caves in ∼60  nm below the crystal surface. X-ray single-crystal diffraction shows that the indentation is due to Ti-induced lattice contraction. Optical studies show that the waveguide is in an NS composition environment, supports TE and TM single-mode propagation at 1.5 μm wavelength, is polarization insensitive, and has a shallow mode field profile and a loss of 0.2/0.3 dB/cm for the TE/TM 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. With the optimized fabrication condition, the waveguide is promising for developing an optical-damage-resistant device that requires a shallow mode field profile.

Electro-optic coefficients of Ti:LiNbO 3 single crystal: erratum

We correct an error in the previous paper [Opt. Mater. Express6, 2593 (2016)]. The electro-optic coefficients γ33 and γ13 that were measured by applying a DC voltage to the crystal via the Al films coated onto the crystal surfaces are the unclamped instead of clamped coefficients. In addition, the acknowledgment part is modified.