Planar Waveguide Optical Coupler And The Coupler-based Optical Devices Developed

Lightwave is widely employed in information technologies, including information transmission, display, storage and detection, etc. The rapid development of optical communication systems in recent years has greatly pushed the research of optical components. The goal of this thesis is to design some novel planar lightwave circuits with low insertion loss and ideal output field or spectrum. Based on the proposed simulation and optimization methods, we design four kinds of novel planar waveguide couplers or optical components based on couplers. Relative experiments are also carried out.First, some studies on simulation and design methods of planar waveguide circuits are carried out: (1) A novel boundary condition, the perfectly matched layer (PML) based on wide-angle finite-difference beam propagation method (BPM) is presented, which can greatly improve the precision of simulation. A number of simulation softwares are also programmed, including a mode-solving method and a BPM (2) In the design of large-scale planar lightwave circuits, a method combining transfer matrix method and digital signal processing (DSP) is introduced. The DSP models for the Arrayed Waveguide Gratings (AWGs) and the Fiber Bragg Gratings (FBGs) are established at the first time.Secondly, some types of planar waveguide couplers are designed and fabricated. In the design of splitters, we do the following work: (1) A 1×8 splitter based on ion-exchange glass waveguide is designed and fabricated. Initial experimental results are also obtained. (2) The optimization of a multimode interference (MMI) splitter based on ion-exchange glass waveguide is also considered. Using the three-dimensional exact mode analysis (3D-EMA) presented, the performances of the designed MMI coupler, including insertion loss and uniformity, are greatly improved. (3) The performance of a large-scale N×N planar star coupler is studied, and some optimization methods are presented. Its feasibility is verified by applying it to a 17x17 planar star coupler, whose uniformity is improved to 0.17 dB. In the design of planar sensor, we do the following work: (1) A novel planar sensor based ontwo-mode interference (TMI) coupler is proposed. By optimizing the structure of the TMI coupler, its linearity error is reduced to 0.01. (2) The planar sensor based on silica is also fabricated, and some experimental results are obtained.In the next parts, we research planar waveguide circuits based on couplers. First, by using the method combining transfer matrix method and DSP, we design some kinds of optical filters based on cascading Mach-Zehnder interferometers. By introducing some optimization methods, such as the genetic algorithm and the hybrid method of genetic and gradient algorithm, the symmetrical/asymmetrical interleaver and the EDFA gain-flattening filter with ideal spectrums are designed.At last, we research the multiplexer/demultiplexer based on MMI couplers: (1) A novel design method is proposed. From the view of finite impulse response (FIR) filters, the spectral response of an MMI-based multiplexer/demultiplexer is analyzed and designed as a whole. (2) Some studies on improving the spectral response of an MMI-based (de)multiplexer are also carried out. By connecting appropriately designed high-order cascaded MMI filters and M-Z filters to a conventional (de)multiplexer, a low cross-talk and flat pass-band spectrum is achieved.