Research On Waveguide And Grating Of Titanium Diffusion Lithium Niobate

In recent years, information industry has been developing rapidly. Due to the high speed and large capacity characteristics of optical communication system, integrated optical devices which are used to build all-optical communication network become a hot topic. For that reason, the waveguide devices, as an important part of integrated optics, receive extensive attention. Lithium niobate(LN) crystal among materials for waveguide devices is widely used due to its characteristics of electro-optic, acousto-optic, nonlinear and photorefractive effect.Fabrication technology of LN waveguide is relatively mature, the most common method is Titanium diffusion and proton exchange. The reasearch of waveguide grating is also developing rapidly based on waveguide technology. The normal preparation technologies of waveguide grating are photorefractive, electron beam etching and laser direct writing, etc.In this paper, Titanium diffusion LN single-mode waveguide is designed and fabricated based on x-cut Li Nb O3. The effect of temperature differences between substrates and photoresist on transmission loss of titanium diffusion LN waveguide is studied. In addition,two experimental processes of fabricating waveguide grating are proposed. Details are as follows:1. The mode dispersion equation of Titanium diffusion LN waveguide are analyzed by optical ray and effective index method. The single-mode transmission conditions of Titanium diffusion waveguide are given by numerical simulation the dispersion equation. According to the single-mode transmission conditions, Titanium diffusion LN waveguides are fabricated and characterized. In addition, the effective refractive index and the mode field distribution of waveguide are measured. The experimental results show that the fabricated waveguides have low loss and single-mode properties.2. The effect of temperature differences between substrates and photoresist on the transmission loss of Titanium diffusion LN waveguide is studied. Titanium diffusion LN waveguides under high and low temperature difference are fabricated and measured,respectively. The experimental results show that larger mode field size and smaller transmission loss can be achieved under a relatively low temperature difference, which is consistent with the simulation results. Therefore, in the fabrication process of Titanium diffusion LN waveguide, the temperature difference between substrates and photoresist should be controlled as small as possible.3. Two experimental processes of fabricating waveguide grating are proposed: one-time Titanium diffusion method and two-times Titanium diffusion method. Waveguide grating fabrication processes are given by combining Titanium diffusion, laser and electron beam direct writing methods, establishing the foundation for fabricating waveguide grating.