Research On The Novel Long-Wavelength RCE Photodetectors

Dense Wavelength Division Multiplexing (DWDM) technology to fully utilize the transmission capacity of optical fibers is widely used in high-capacity, ultra-long-distance, high-speed optical communication systems. In DWDM optical communication systems, long-wavelength RCE photodetectors are the key devices. In order to further improve the performance of DWDM optical communication systems, studing the novel RCE photodetectors are important. In this dissertation, taking full advantages of the subwavelength gratings, such as simple processes, easy integrations, high diffraction efficiencies and so on, the new type of1550nm high efficiency and flat-top steep-edge RCE photodetectors were designed based on the subwavelength gratings. Thus they can be used in the optical communication systems.The main research work and achievements are as belowing:1. The one-dimensional rectangular subwavelength gratings were analyzed based on rigorous coupled-wave analysis method and planar dielectric waveguide theory, which was simulated using MATLAB. For subwavelength polarization gratings based on SOI (Silicon On Insulator) material, the relationships between the subwavelength grating reflectivity with the periods, the duty cycles of the subwavelength gratings were simulated. The subwavelength gratings with high reflectivity were designed. The TM mode reflectivity is as high as99.98%.2. A new type of1550nm high efficiency and narrow linewidth resonant cavity enhanced photodetector based on a cascaded subwavelength grating filter was designed. Its efficiency can be as high as98.5%, and FWHM is0.09nm of TE mode.3. Novel1550nm flat-top steep-edge one-cavity subwavelength grating filter and two-coupled-cavity subwavelength grating filters were designed. Based on the new type filters we designed, the novel1550nm Si-based flat-top steep-edge and high-quantum-efficiency RCE photodetector with two-coupled-cavity subwavelength grating filters was designed. In the final design of the photodetector, the TE mode3-dB linewidth is0.78nm, the ripple of this novel Si-based photodetector is almost0dB, flat-top quantum efficiency is as high as94%. Then the novel1.55μm flat-top steep-edge photodetector was designed based on two-coupled-cavity subwavelength grating filters and inclined top mirror.4. In experiment, the rectangle subwavelength grating based on SOI had high reflectivity ranging from1460nm to1610nm of TM mode, which matched our simulations perfectly.5. In experiment, The TM mode quantum efficiency of this novel photodetector with subwavelength grating structure increased by47.99%comparing to the traditional PIN photodetector.