Studies On High-Performance Photodetector Based On Micro/Nano Structures

With the rapid progress of large capacity, high-bit-rate, long-haul WDM optical fiber communication systems, at the same time, optoelectronic devices used in WDM systems are confronted with grim situations. It will be continuously updated to cope with the high performance needed for future data transmission systems. The optoelectronic integrated devices based on micro/nano structures are the way of the future due to their advantages of compact, high performance, simple manufacture technology and low cost.In this dissertation, the high-performance photodetector based on micro/nano structures was studied. Both theoretically and experimentally, mainly including wavelength-selective photodetector based on Fabry-Perot cavity and microring resonator were studied. The main contents and innovations are listed as follows.1. The theoretical model of evanescently-coupled waveguide photodetectors is established. The working principle of the device was studied. The quantum efficiency and high-speed response of the device were analyzed in theory. The fabrication processes of long wavelength waveguide photodetector are developed and optimized. The long wavelength waveguide photodetectors with different lengths> different electrodes were fabricated. The performances of which were compared.2. The theoretical model of F-P cavity was established by using transfer matrix method. By using this model as theoretical guidance, we completed the experimental verification. We also designed two novel wavelength selective waveguide photodetectors by introduction of F-P cavity in waveguide photodetectors. The integrated device was made by bonding the F-P cavity filter to waveguide photodetector in the horizontal direction. The BCB was used for this bonding. First, the performance analysis of the integrated device was completed in theory. Then the integrated devices were fabricated successfully. The two measured response peaks both locate at1538nm. The spectral response linewidth are both about0.3nm.3. A novel integration of Si F-P cavity filter with long wavelength waveguide photodetector was proposed, which consists of Si F-P cavity filter waveguide and long wavelength photodetector. First, the performance of the Si F-P cavity filter waveguide was analyzed in theory. Then the performance of the integrated device was analyzed, which was integrated by silicon F-P cavity filter waveguide and photodetector in the level. Si F-P cavity is constituted by a Si/Air DBR mirror、Si cavity and a Air/Si DBR mirror. Wavelength tuning was achieved through changing the refractive index of DBR or the cavity length of the F-P cavity.4. A single micro-ring、series-cascaded micro-ring and parallel-cascaded micro-ring resonator filters were designed and fabricated. We have investigated the working principles of microring resonators and presented the formulas for the transmission spectrum of a single micro-ring resonator、series-cascaded micro-ring resonator and the parallel-cascaded micro-ring resonator filter. In addition, the formulas for the performance parameters of microring resonators are presented. Transmission spectrums of the devices were tested. The experimental results are basically consistent with theoretical results.5. A novel integration of waveguide photodetectors with Silicon-on-Insulator micro-ring resonator on silicon substrate was designed and fabricated successfully. The SOI micro-ring resonator was used for wavelength selectivity. The resonance characteristics of the device were obtained by experiment. The responsivity of the photodetector at through port was0.538μA/W at wavelength of1556nm and a reverse bias of1V. The free spectral range (FSR) of the hybrid integrated device was about24nm. 6. A novel integration of long wavelength photodetectors on Silicon-on-Insulator racetrack resonator was designed. The racetrack resonator was used for wavelength selectivity, and the optical transmission process of the racetrack resonator was simulated by beam-propagation method. The transmission characteristic of the racetrack resonator with a multimode interference coupler has been numerically simulated. The result shows that the free spectral range (FSR) is inversely proportional to the length of the racetrack resonator. The FSR decreases as the increase of the length of straight waveguide sections or the radius of rings. The calculated peak quantum efficiency of the integrated photodetector is about88%at1550nm, and the FSR of the device is about17nm.