Silica-on-Silicon Array Waveguides Gratings

Planar Lightwave Circuit (PLC) is one of very important research areas in optoelectronics. The technology of silica-based PLC is a novel integrated photonics device technology developed since the end of 1980s. Due to its full processing compatibility with silicon-based microelectrics, the silica-based PLC has been attracting comprehensive concerns, and becomes one of the research and development hotpoints in photonics all over the world. Especially, the silica-based array waveguide gratings (AWG) is one of the most focus points in PLC devices research, as a result of it has small wavelength space, suitable for optics-integrated and mass-yield. This dissertation studies on the theoretics, design, fabrication and test of the silica-based AWG, and gets some valuabel results that is foundational to promote the practical applicaion of our country's integrated photonics divices. In this work, waveguide performances are analyzed, and the distributions of model field are gotten by using Maxwell functions, as well as the effcetive index. Effective Index Method (EIM) and Beam Propagation Method (BPM), which are very effective way to design and optimize waveguide devices at present.The functions of arc waveguides effective index with arc radius are studied by using the BPM and conjunction equations.As well as the coupling loss between arc waveguides and directly line waveguides, which are the bases of the studies of waveguides devices. Polarization Dependence Loss (PDL) is one key factor to limit application of the planar waveguide device, and it is a tough problem to cope with. PDL is mainly caused by thermal stress in planar optical waveguide. By studying the stress and strain theory in multi-layer structure, the author analyzed and deduced the analytical formulas for the thermal stress and strain in the waveguide core layer and the whole waveguide layer. These formulas reveal how the characteristic of the compound material to affect the distribution of the thermal stress and strain. The results show that if the structure and material parameters are chosen properly, the polarization independent device can be obtained. The basic theories, characteristic specs and parameter definitions of AWG devices are introduced comprehensivily. AWG spectral response theoretic model that can estimate and optimization the AWG's normalization spectrum accurately are shown based on the Model Coupling Theory.A method of array waveguides arrangement that can realize the AWG waveguides arrangement easily are developed. According to the trends of the optical network evolution, that the bone network focus on high wavelength density and huge information bulk as a result that the much more wavelength with small space Mux/Demux are commended, and that the access network focus on low-cost and update-easily as a result that it needs few wavelength with large space Mux/Demux, the author designed and optimized two kinds of AWG. One is 40λ, 100GHz space flat-top DWDM AWG, the other is 8λ, 2500GHz space CWDM AWG. Many problems such as band-ripple of DWDM AWG and array waveguides arrangement of CWDM AWG are studied and optimizated resolvent are released. As the optical waveguides devices have rigorous requirements to the waveguides effective index, geometry dimension, uniformity, sidewall roughness, etching anisotropic, stress and so on. The whole silica-on-silicon PLC fabrication process are studied comprehensively, especially, on the waveguides index-controlled, waveguides etching model development, etching mask optimization and waveguides performance improved by anneal process based on quantities of experiments. Some creative methods are developed to improve the fabrication results. Measure techniques including Scan Electronics Microscope (SEM), Atom Force Microscope (AFM) and Near Infrared Spectroscopy (NIRS) are used to confirm the experiments which have approving results. At last, the propagation loss and coupling loss of straight waveguides etched with different masks and standard single model fiber were test and analysised. The two kind of AWGs that design and fabrication in this work are characterized by utilizing the test equipment. The test results revealed that the AWGs have good bandwidth, low band-ripple, low insertion loss except that the crosstalk are still below the requirements and need to improve in the later works.