Research On High-Order Lithium Niobate Waveguide Bragg Grating Based On Phase-Mask Method

In recent years,Lithium niobate(LN)crystals have been widely used as the base material for optical integrated devices because of their good thermal stability and photorefractive sensitivity in visible light.At the present stage,fabrication technology of LN waveguide is relatively mature.However,Bragg waveguide gratings developed on waveguides become one of the most important integrated devices.In this thesis,the properties of high-order uniform,phase-shifted and linearly chirped Bragg waveguide gratings based on Ti-diffused LN waveguides are studied.The experiment fabricating second-order uniform and linear chirped Bragg waveguide gratings on Ti-diffused LN waveguides by phase mask technique is studied.Details are as follows:1.The properties of high-order uniform Bragg waveguide gratings are studied.The influence of saturation coefficient and grating order on the reflection spectrum of high-order uniform Bragg waveguides is summarized.The maximum reflectivity and zero bandwidth can reache the maximum at the optimum saturation coefficient,and the larger the grating order is,the narrower the zero bandwidth is,but the optimum reflectance is equal.2.The properties of high-order ?-phase-shifted Bragg waveguide gratings are studied.The influence of phase shift position,saturation coefficient and grating order on the reflection spectrum of high-order ?-phase-shifted Bragg waveguide gratings is analyzed.The performance of ?-phase-shifted Bragg waveguide gratings is the best when the phase shift point is in the middle of the grating.The double passband gap,reflectivity of resonant peaks and splitting point are the largest at the optimum saturation coefficient,and the larger the grating order is,the narrower the double-pass band gap is,but the resonant peak and the split point reflectivity are equal.3.The properties of high-order linearly chirped Bragg waveguide gratings are studied.The influence of saturation coefficient and grating order on the reflection spectrum of high-order linear chirped Bragg waveguide is summarized.The maximum reflectivity of different order is the highest when the saturation coefficient is optimal.Under the optimal saturation coefficient,the larger the grating order,the lower chirp coefficient,total reflection bandwidth and maximum reflectivity.4.The experimental scheme of second order uniform and linear chirped Bragg waveguide gratings based on the phase mask method is designed.The experiments of high-order Bragg waveguide gratings by phase mask method are studied.The influence of different experimental parameters on the Bragg waveguide gratings is analyzed.Experiments are carried out and the possible causes of the experimental results are analyzed.