科研之友
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摘要
Based on an analysis of the grating coupler, a high-efficiency hybrid surface-normal coupler, which is a combination of a coupler grating, reflector grating and a bottom mirror, was designed to couple a planar waveguide and a single-mode fiber. The negative second-order reflection was reduced by destructive interference by selecting a reasonable spacing between the reflector and the coupler grating. The negative first-order diffraction to the substrate was reflected by the bottom mirror, which was realized by Au-Au bonding. The etch depth of the coupler grating was optimized to increase the coupling efficiency between the grating and the fiber. The highest coupling efficiency of 89.5% at 1550 nm was achieved for surface normal coupling.
