Research On Wavelength-Selective Waveguide Photodetectors In Optical Communication System

With the rapid expansion of the Internet, higher speed and capacity are required. The dense wavelength division multiplexing (DWDM) has satisfied these requirements. Multiplexer/demultiplexer are the key components in DWDM systems. It has been the focus that how to accomplish the demultiplexing and receiving in the receiver.As the key component in the receiver, wavelength-selective semiconductor photodetector should have following advantages:high responsivity, large bandwidth, well reliability, good wavelength selectivity and it should be convenient to integrate the photodetector and other devices. The wavelength-selective waveguide photodetector can meet these requirements. It can release the trade-off between the quantum efficiency and bandwidth so that the high efficiency and large bandwidth can be realized at the same time. It is also suitable for the large scale integration (LSI). Bright future can be expected for WGPD.This thesis is mainly concerned with a novel wavelength-selective waveguide photodetector. The work is listed as follow:1. The DBRs with different periods and materials are analyzed. The transmission characteristics of the F-P cavity with different reflectivities and cavity lengths are investigated.2. The simulation of the side-illuminated type photodetector is performed. The results from the simulation include dark current, quantum efficiency,3dB frequency bandwidth. The Gauss-doping is also applied to the absorption layer. Comparing the two kinds of photodetectors, the characteristics of the Gauss-doping are better. The dark current of the later is as low as10-16A, and the3dB frequency bandwidth of113GHz, the responsivity of0.034A/W and the quantum efficiency of94.5%are obtained.3. A novel wavelength-selective waveguide photodetector is designed in this thesis, which consists of a waveguide photodetector (WGPD) and a Fabry-Perot (F-P) cavity filter. The peak wavelength of the integrated device is at1538nm. The coupling efficiency between the filter and photodetector is27.59%. The3-dB line-width of0.3nm, quantum efficiency of25%are theoretically obtained.4. The analysis of evanescent coupling in the waveguide photodetector is performed. The photodetector is constructed by the PIN photodetector and SOI waveguide with BCB polymer. The BCB layer is as thin as100nm so that the light can be guided into the photodetector through evanescent coupling. Two structures are analyzed in light field distribution and transmission loss. The optimization of the BCB layer thickness is also performed.5. The fabrication of InP-based PIN photodetector and GaAs-based F-P cavity filter is accomplished with the cooperation of Hu Fuquan. The BCB polymer is used to integrate the filter and photodetector. The testing of device is carried out and the test result is analyzed.