Study Of A Testing System For Waveguide-integrated Optical Sensors Based On Grating Couplers

Recently,with the quick development of Internet of Things technology,the requirements of high-performance,low-cost,and minimized sensors are boosting.Among current sensing techniques,gas sensors are essential components for tremendous applications in areas of aerospace,petrochemical,environmental protection,industrial safety.To date,several approaches have been proposed and demonstrated for gas sensing.Optical gas sensors based on silicon waveguides are one of the promising candidates and attract great attention due to the advantages of high-density integration,strong environmental adaptability,long service periods,low failure rates,fabrication compatibility with the CMOS technology.To develop optical sensors based on silicon waveguides,it is inevitable to comprehensively control environmental parameters,namely,temperature,gas concentration,and pressure,as well as to probe the optical and electrical properties of silicon devices.However,current silicon photonic testing systems are developed for optical communications and optical interconnects,which cannot fully satisfy the requirements of developing silicon photonic sensors,hindering the development of the research and development of optical gas sensors based on silicon waveguides to some extent.To overcome this limitation,in this Thesis,the author studied silicon grating couplers in near-infrared and mid-infrared spectral regions and developed a waveguide testing system.The main content is as follows:1、The author theoretically designed silicon-based waveguide devices based on grating coupling.Strip waveguides and slot waveguides were simulated based on a silicon-on-insulator wafer.The ability of the designed devices for sensing was discussed theoretically.After that,the author designed grating couplers with center wavelengths of 2 μm.Moreover,the coupling alignment tolerance between an optical fiber and a silicon chip was discussed numerically.2、The author experimentally studied the silicon-based grating couplers.The grating couplers with center wavelengths of 2 μm were studied experimentally.The effect of the fiber position on the coupling efficiency was studied experimentally.The influence of the grating coupler structure on coupling alignment tolerance was studied experimentally.3、The author developed a method of fiber-waveguide automatic coupling.Inplane automatic coupling of an optical fiber and a silicon chip was studied.The author experimentally tested and compared two scan paths: a round-trip scan path and a spiral scan path.Then,based on the experimental results,the author proposed and demonstrated a new scan method,namely,a direction-judged scan path.4、The author constructed a waveguide testing system for optical sensing.According to the requirements of developing waveguide-integrated optical sensors,the author designed and built up the system.Moreover,the author developed a program based on LabVIEW software for system control.