| The rapid development of Wavelength Division Multiplexing (WDM) communication systems demands optoelectronic devices with high performance, high integration and low cost, while the traditional discrete ones could not meet the requirements. Photodetectors with flat-top and steep-side response, combined filters have attracted more and more attentions due to their advantages of good wavelength selectivity, small size and low cost.As a wavelength-selective element, micro-ring resonator becomes an ideal candidate to realize photodetector with wavelength selectivity for its low cost and high integration. Micro-ring photodetector has merits of high quantum efficiency, small FWHM (Full Width at Half Maximum) and compact structure. Compared with vertical cavity RCE-PDs, it needn't Bragg reflectors (DBR) and is more beneficial to planar integration with incident beam from side, which shows great prospect in the Optics Electronics Integrated Circuit (OEIC) and Dense Wavelength Division Multiplexing (DWDM) optical communication system.This dissertation is mainly concerned with photodetector with wavelength selectivity in WDM system and micro-ring resonator. The major contributions are outlined as follows:1. The parameters of micro-ring resonator were calculated and stimulated in theory:the coupling coefficients between micro-ring and straight waveguide, two micro-rings, waveguide in racetrack and straight waveguide were analyzed applying coupled mode theory. The transmission spectrums of micro-ring resonator, series-cascaded micro-ring resonators and parallel-cascaded micro-ring resonators were calculated using transmitted matrix method. Based on the study on micro-ring filter, the conclusion that flat-top and steep-side response in filer could be obtained by cascaded micro-rings was made.2. A series-cascaded micro-ring photodetector with flat-top and steep-edge response was proposed. It consists of four series-cascaded micro-ring and the absorption layer is embedded in the last one. The flat-top and steep-edge response could be achieved by reasonable coupling coefficients between micro-rings. Simulation results show that the maximum value of the quantum efficiency in the bandpass is 98.85%; 0.5dB,3dB, and 20dB bandwidth is 0.4nm,0.48nm, and 1.2nm respectively; FSR reaches 53nm, which meet the requirements of WDM system. Compared with single micro-ring photodetectors, this photodetector has high quantum efficiency, wide FSR, good flat-top and steep-edge response.3. Another photodetector with flat-top and steep-edge response based on parallel-cascaded micro-ring was proposed. The response is obtained by designing a racetrack resonator with a waveguide photodetector as absorbing cavity following parallel-cascaded three micro-ring resonators as filter cavity. The flat-top and steep-edge response could be achieved by reasonable length of straight waveguide between micro-rings. Simulation results show that the maximum value of the quantum efficiency in the bandpass is 99.8%; 0.5dB,3dB, and 20dB bandwidth is 0.3nm,0.32nm, and 0.5nm respectively; which meet the requirements of WDM system. Compared with single micro-ring photodetectors, this photodetector has high quantum efficiency, narrow response linewidth, good flat-top and steep-edge response.4. An InGaAsP/InP micro-ring waveguide monolithic photodetector was presented. The epitaxy and the design for the layout were completed, and the research on fabrication processes was carried out. A racetrack resonator instead of micro-ring resonator increases the couplings between waveguides and the vertical coupling is used between waveguide and active layer.5. A measurement platform was built and the experiment of micro-ring resonator device in the manner of the coupling between fiber and waveguide was carried out. The results show that the coupling efficiency between the micro-ring and straight waveguide is 16% and that between the fiber and waveguide is 38%. The detector response and coupling efficiencies were analyzed. All work laid a foundation for further research on the micro-ring photodetector. |
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