Study On Nano-waveguide Grating Coupler Based On Silicon Substrate

Efficient light coupling between a silicon photonic waveguide on chip and an optical fiber is critical for integrated optics. A widely used way is to make periodic perturbations of the waveguide's refractive index by introducing some etched slots on the silicon waveguide. As waveguide grating coupler has many advantages such as versatility, high efficiency and low power consumption, it has been widely used in the field of integrated optics.We studied the basic principles of the waveguide grating coupler based on silicon substrate in this thesis, fabricated a fully-etched grating coupler and tested the coupling features of the coupler. A metallic grating coupler based on SOI material structure is designed. The device structures of the metallic grating coupler are designed with the COMSOL Multiphysics RF module, and we also analyzed the 3-dB bandwidth and tolerance angle of the metallic coupler.A number of achievements were obtained through the theoretical and experimental study of the grating coupler:(1). We constructed a coupling testing platform. The fully-etched grating coupler is fabricated by Electron Beam Lithography(EBL). The preliminary test results are obtained of the relations between the coupling efficiency with the incident wavelength and incident angle. We also calculated the loss per millimeter when the light transmits in the silicon waveguide.(2). We proposed a metallic grating coupler based on SOI material structure based on Comsol to realize coupling between a silicon waveguide and an optical fiber. Our coupler has a ultrabroad bandwidth, which is about triple of normal etched grating coupler. The coupler also has an extremely compact dimension(the grating length is 5?m). The incident wave is TM polarization and the incident angle is 10°.