Study Of Echelle Diffraction Grating Spectrometer Based On SOI

Spectrum analysis plays a crucial role in modern society. With the development of spectrum technology, computer and MEMS fabrication process, spectrometers trend to miniaturization, portability, fast and real-time measurement.In this paper we put forward a design scheme of an silicon-on-insulator (SOI) material based micro-spectrometer by using etched diffraction gratings as the spectral component, and an optical sensor formed by this spectrometer structure cascaded with a ring resonator.SOI based etched diffraction grating micro-spectrometer uses the principle of grating diffraction, adopts the design scheme of three-stigma method, separates signals of different wavelength according to space positions, spread to linear array sensor through different output waveguides, and then the spectral composition of the input light is obtained. The thesis uses scalar diffraction theory to establish a theoretical model of the grating diffraction effect, gives the structure parameters and simulation results of the micro-spectrometer (realizing129-output channels and0.25nm-resolution spectrum detection), designs the mask of the device.An optical sensor formed by a SOI-based etched diffraction grating spectrometer cascaded with a single ring resonator can be used to detect the change of refractive index of the samples to be tested, analyze the concentration of the samples, chemical composition and so on. The sensor has the characteristics of high integration, high detection sensitivity. Different from the conventional optical sensors, it doesn’t need expensive spectrum analyzer or tunable lasers, but only need broadband light source and detector, which reduces the cost of the sensing system. The etched diffraction grating inside not only plays the role of spectrum analysis, but also equals to a resonator. It cascades with a single ring resonator, producing the Vernier effect, increasing detection sensitivity, which can do optical detection under two working modes (coarse and fine measurement mode) with different sensitivity. What’s more, this structure is the simplified version of the existing optical sensor formed by double rings cascaded with AWG. Theoretically the detection sensitivity of the device can reach10-6RIU.Experimentally, the micro-spectrometer with five output channels and lOnm adjacent channels wavelength space was fabricated successfully. The spectral response curves for each channel were measured, which verifies the feasibility of the design.In the first chapter of this article, the significance, current development of spectrometer are introduced, and current several spectrometer design schemes and their advantages and disadvantages are analyzed, thus the main content of this article--SOI based etched diffraction grating spectrometer and optical sensor are put forward. The second chapter briefly introduces the theoretical basis of spectrometer, including the theoretical basis of spectrometer realization, basic characteristics of spectrometer and the basis studied in the article--the basic theory of etched diffraction grating, including its aberration theory, three kinds of etching diffraction grating design methods (one, two, three-stigma method) for comparison, and the details of numerical simulation method for etched diffraction grating are also introduced. The third chapter expounds the main content of this paper--design scheme of SOI based etching diffraction grating spectrometer, including the overall design scheme, waveguides and grating structure design. The fourth chapter describes a high-sensitivity optical sensor formed by the micro-spectrometer and a ring resonator, the structure and working principle of this optical sensor are given, and the detection sensitivity under two working modes are analyzed. The fifth chapter mainly introduces fabrication and testing methods of the micro-spectrometer, including the mask design and the main steps and process of the device fabrication, testing methods and the analysis of the testing results.