Research On Theory And Experiment Of Integrated Demultiplexing Photo-Detectors For WDM System

With the rapid development of information technology,the increasing demand for bandwidth of telecommunication has been promoted.One of the promising technologies is wavelength-division multiplex(WDM) which has been developed rapidly in the long haul communications. Demultiplexing and receiving technology ensures WDM be applied into communication system successfully.This thesis researches on the integrated demultiplexing photodetector and microstructures in WDM system.The main research work is listed below:1.We investigate a novel demultiplexing photodetector integrated with an arc absorbing cavity and analyz its quantum efficiency of TE and TM lightwave.The maximum quantum efficiency of TE lightwave can reach 82%,while maximum quantum efficiency of TM is 66%.As the absoption of arc absorbing cavity,quantum efficiency is determined by arc-radius,rather than the area of device.When the area of device is small,an appropriate arc-radius will lead to higher quantum efficiency than the wedge-type photodetector.The spectral response linewidth of this novel photodetector can reach 0.5nm,which indicates that this photodetector has an excellent performance of lightwave selectivity.2.According to the characteristics of high-index-contrast sub-wavelength grating(HCG),we calculate the reflectivity and bandwidth of HCG via rigorous coupled-wave analysis method.The results indicate that HCG has a high reflectivity,that is 0.99 and a wide reflective bandwidth,that is△λ/λ≈32%.3.We design HCG to be used as reflector of Resonant-Cavity-Enhanced (RCE) photodetector.Long-wavelength material InP is selected to calculate the quantum efficiency.The result indicates that RCE photodetector integrated with HCG has an excellent performance of quantum efficiency,that can reach 99%.4.Two different programs to achieve an arc absorption microstructure are proposed and studied in experiment.One is realized by air-gap technique,in which one of epitaxy layers is etched by selective chemical wet etching techniques.With the air-gap,the cantilever will bend for the tangential stress and an arc absorption cavity is obtained. The radiuses of the fabricated arc microstructures are 72μm,286μm, 643μm and 1143μm.The other arc microstructure is realized by dynamic etch mask technique.With this technique,the angle range of arc microstructure can be controlled by varying the initial and the final concentration of solutions,and the radius of arc microstructure can be controlled by varying the time of titration.