Implementation Of Optical Wavelet Filter By Waveguide

There are several kinds of optical systems for wavelet transform, which can perform continuous or discrete wavelet transform. They are different in transform pattern, complexity of system configuration and numeric precision. However, wavelet filters are core parts of all the systems. At present, film, holograph and grating are widely used to implement wavelet filters, but they are not precise enough for some demanding application due to errors. The application of optical waveguide to design wavelet filter has great advantages, which enjoys higher numeric precision, smaller device size, and better performance stability. Funded by the National Science Foundation of China (NSFC), this thesis conducts an investigation in theory and practice for implementation of wavelet transform in the form of integrated optical devices.Mode theory is the theoretical basis of waveguide-related research. Firstly, the thesis introduces the diffusion behavior of light that passes through planar waveguide based on mode theory. Then, the analytic and numeric solution to solve computational problems of bar shaped waveguide is discussed. By taking the algorithm of FD-BPM as an example, the application of numeric solution is presented. Secondly, the property of optical energy coupling between two adjacent waveguides is introduced based on principal of interference, physical structure and features of directional coupler and MZI are also discussed. Besides, an example is simulated in this chapter. Thirdly, optical lattice FIR filter is discussed in Z domain according to the theory of traditional FIR filter, filter structure, circuit parameter acquisition are both provided. Then, an additional improved configuration of the lattice filter called half-band filter (HBF) is following. Finally, based on HBF and wavelet transform theory, the circuit configuration and parameter acquisition of QMF filter are given. According to the filter structure, several major factors that affect the filter performance are discussed. In the fifth chapter, procedure to produce silicon dioxide waveguide and related planar devices is introduced, the error caused by the manufacture technique is also considered.Through theoretical research and experimental simulation, It is proved that implementation of wavelet filter by waveguide is realizable. It is advantageous over others categories on aspects of numeric precision, long-term stability, etc. However, the disadvantages of manufacture and waveguide's self-constraints heavily hold back its application, such as cost, technique complexity, quality control. Anyway, a novel solution to design wavelet filter is adopted in this thesis, which can be useful for further research.