An Experiment Study On Ti⁴⁺-diffused Lithium Niobate Doped With Zr⁴⁺

LiNbO3 crystal has been studied extensively by researchers owing to its excellent electro-optical and acousto-optical effect and nonlinear optical effect, which can be used to make various optical waveguide devices. But the photorefractive effect of Li NbO3 crystal hinders the development in related devices, suppressing photorefractive effect of LiNbO3 crystal effectively can develop its application in frequency conversion as well as in optical parametric oscillation. Compared with Mg2+(5.0 mol %), optical-damage-resistant threshold concentration of Zr4+ is very low(2.0 mol %) which ensure the Zr4+-doped LiNb O3 crystal maintain a relatively high optical quality when suppressing photorefractive effect. In this paper, we fabricate several optical-damage-resistant Zr:Ti:LiNbO3 strip waveguides and study its optical properties. The main work and achievement includes:(1). We studied the diffusion property of Zr4+ ion in LiNbO3 crystals with SIMS first. The results showed that the diffusion of Zr4+ ion was in accord with the usual regulation. From the measured profiles, important diffusion parameters were obtained, such as diffusion constant, activation energy, surface concentration, and solubility. Furthermore, we researched the effect of Zr4+diffusion on refractive index of LiNbO3 crystal by prism-coupler method. the results showed that doping of Zr4+ had little effect on ordinary light as well as on extraordinary light compared with Ti4+, which laid the foundation for fabricating a photorefractive-damageresistant Zr4+-doped Ti4+-diffused Li NbO3 waveguide.(2). Fabrication of the Zr: Ti: LiNbO3 strip waveguides was developed. To fabricate the waveguide, a Z-cut pure congruent LiNbO3 substrate was prepared, then followed the process Zr4+-doped, Ti4+-diffused., a Zr: Ti: LiNbO3 strip waveguide was fabricated with 8μm width titanium strip. The Li2 O content in the crystal, determined from measured birefringence, was 48.6%. Furthermore, we built the coupling system on the end face of a congruent waveguide for acquisition of near-field pattern, and found that the waveguide could transport the single-mode light of 1.5μm well. The transmission loss in the strip waveguide was 6.7db/cm.(3). We fabricated a near-stoichiometric Zr:Ti:LiNbO3 waveguide based on congruent waveguides treated by VTE. The Li2 O content in the crystal, determined from measured birefringence, was 49.8%,.the waveguide could transport the single-mode light of 1.5μm well and the transmission loss in the strip waveguide was 7.7db/cm and 7.5db/cm respectively. According to the diffusion of Zr4+ in LiNbO3 crystal and conservation of mass, the concentration of Zr4+ was 2.4mol% and 1.0mol% in congruent waveguides and near-stoichiometric waveguides, which was higher than the optical-damage-resistant threshold concentration respectively.The work provides the basis of further research work.