Research On New Structure Of High-speed And High-power Optical Waveguide Photodetector

An analog photodetector is a kind of photoelectric device to realize the photoelectric conversion.A high speed and high power photodetector can be used directly to drive antenna in radio-over-fiber(ROF)and Phased Array Radar(PAR)systems.However,it's difficult to meet the needs of high-speed and high-power for the traditional waveguide and normal surface photodetectors.In this thesis,the model of single mode waveguide with large cross section is first analyzed.However,the practical application of this structure is greatly limited because of the large coupling energy loss and the difficulty in coupling energy from the lower waveguide to the upper waveguide.Then,a symmetrical horizontal directional coupling waveguide photodetector is presented,which works on the fundamental super mode and the second super mode.The cross section can be properly enlarged to meet the coupling requirement.In this thesis,the characteristics of symmetrical horizontal directional coupling waveguide photodetector is mainly studied from the following aspects:1.The structure of the symmetrical horizontal directional coupling waveguide photodetector is proposed,and the structure parameters of the detector are designed by a lot of MATLAB calculations and BeamProp software simulations.2.According to the structure parameters of the symmetrical horizontal directional coupling waveguide photodetector,the effective index method is concretely used to analyze the waveguide modes.The fundamental super mode,the first super mode and the second super mode are calculated.According to the specific structure of the detector,we can analyze that the detector should work on the fundamental super mode and the second super mode.Finally,the super mode matching condition of the detector is verified.3.The epitaxial layer structure of the detector is designed according to the Uni-Traveling-Carrier theory.Combined with the specific structure of the detector,the performance of the detector is analyzed by ATLAS and BeamProp software simulations and MATLAB calculations.It is verified that the photocurrent distribution is uniform,and the detector has little effect on the offset from the central waveguide.Next,the saturation current and the 3dB bandwidth of the detector are calculated.The saturation current of the detector is 460 mA,the responsivity and the 3d B bandwidth achieve at 1.02A/W,1.8GHz.4.The processing flow of symmetrical horizontal directional coupling waveguide photodetector is designed according to its structure,such as the detector substrate growth,mask making,lithography,etching,electrode fabrication,substrate thinning and waveguide cutting and other specific aspects to introduce each step of the process and its purpose.