Design?fabrication And Characterization Of APE MgO:LiNbO₃ Ridge Waveguide

Lithium niobate (LiNbO3) ridge waveguides are widely used in electro-optic-modulator, micro cavity, photoelectric sensing, etc, due to the excellent electrical and optical properties. However, currently the fabricated waveguide devices have many shortcomings, such as large propagation loss, high cost of production, complex technical processes, etc. Based on the theoretical analysis and numerical simulations, a novel method for fabricating low cost and high performance LiNbo3 ridge waveguides by synthesizing the techniques of annealed proton exchange (APE) and direct diamond blade dicing is proposed in this thesis.The characteristics of propagation loss and mode field distribution in the new ridge waveguide are experimentally investigated. The contents are concluded as follows:The optical properties of lithium niobate crystal and the development status of LiNbo3 waveguides are firstly introduced. By establishing the physical model for the refractive index distributions in the waveguide area, the relationship between proton exchange condition and refractive index distributions are achieved. Then, the single mode cut-off condition of the ridge waveguide and the optimum waveguide size are obtained by using the effective refractive index method. On this basis, the mode field characteristic of the designed ridge waveguide is simulated and analyzed.In the experiment, the preparation process of annealed proton exchange is firstly studied and the LiNbo3 ridge waveguide is fabricated by precise dicing with the diamond blade. Then, the factors which may influence the dicing effect are analyzed. High quality ridge waveguide is successfully fabricated by optimizing the parameters of the diamond blade and the cutting speed. The test platform is built for measuring the propagation loss and the light mode field in the ridge waveguide. Our experimental results show that the fabricated waveguide can effectively confine the near infrared lights with low propagation loss and good beam quality. For the 1064nm waveband waveguide, the minimum propagation loss of 0.49dB/cm can be reached under the conditions of 1hr33min proton exchange, 5hrs45min annealing and waveguide width of 4?m; However, for 1550nm waveband ridge waveguide the propagation loss as low as 0.31dB/cm is achieved when the proton exchange time,annealing time, and the waveguide width are set at 2hrs7min, 5hrs45min, and 8?m,respectively.