Design Of Polymer-based Waveguide Grating Couplers

The waveguide grating coupler is a kind of device which allows light coupling from the waveguide to the fiber through etched gratings. Compared to the lens fiber, the grating coupler has some advantages such as more flexible and less difficulties during packaging.As a waveguide material, polymer can be compatible with the substrate very well, it makes the fabrication simple, also achieves better flexibility. All these advantages lead a broad prospect for polymer. The polymer involved in this article which named PSQ was developed by the polymer photonics group of the Dalian University of Technology.In the introduction, we present some methods for coupling light from the waveguide to the fiber first, and then compare the differences among them. We discuss the background and the potential application of the grating coupler. Contrasting with polymer, we introduce the grating coupler fabricated with some other materials such as SOI\the InP membranes and the other polymer used in other universities.In Chapter2, the structure and the coupling principles of the grating coupler are described. We analyze the main reasons for the optical loss through the coupling procession from the waveguide to the fiber. The conditions of the grating’s parameters are presented, include the Bragg Condition and the Thickness of Cladding Condition. Finally,we derivate the expression of the coupling efficiency.The main content of Chapter3is the simulation of the grating coupler in CAMFR. For both the infrared λ=1550nm and the near-infrared λ=850nm,we simulate the coupling efficiency of the grating coupler. While trying different structures to level up the coupling efficiency, we calculate the coupling efficiency of each design. The effects of the parameter deviation on the coupling efficiency are also showed.In Chapter4, researches on the fabrication technology are presented. Nano-imprint is used for fabricating grating coupler now. With this method we should choose the appropriate material for the imprinting template as well as the etching process for the template. The deposition the high refractive index cladding was also studied. Finally, we design the special fabrication for polymer grating coupler with SiN high index cladding.In the final chapter, we compare the measuring results with the simulating results. Consequently, we demonstrate the feasibility of the design and the reliability of the simulation.