Research On Photonic Integrated Devices With Silicon-Based Plasmonic Slot Waveguides

With the rapid development of the mobile internet,the data capacity is exploding rapidly,which requires the continuous improvement in the capacity of optical fiber communication networks.Optoelectronic devices in optical fiber communication networks are developing with large bandwidth,miniaturization and integration.Silicon photonics devices are compatible with complementary metal-oxide-semiconductor technology and can be manufactured on a large scale,leading to its wide study in optical fiber communications.Plasmonic devices can break through the limit of optical diffraction limit,confine the optical field into deep sub-wavelength dimensions,greatly enhance the lightmatter interaction,and reduce the size of optical devices,having the potential to achieve large-bandwidth,small-size and high-integration optoelectronic devices.Aiming to realize large-bandwidth and small-size optoelectronic devices,this thesis focuses on the siliconbased plasmonic slot waveguide(PSW)structure,and studies the photodetector,polarization division multiplexing optical receiving chip and coherent optical receiver that combined with the PSW and graphene.The main research achievements are summarized as follows:(1)Utilizing the ultra-small PSW and microcavity structures,the tunable plasmoninduced transparency phenomenon is studied.Using the silicon-plasmonic tapered coupler structure,the efficient coupling of light from the silicon waveguide to the PSW is theoretically and experimentally demonstrated,which lays the foundation for the subsequent research on silicon-based PSW devices.(2)The graphene-on-PSW photodetector with simple process and high performance is proposed based on the photoconductive effect.In this scheme,a simplified two-step photolithography production process is achieved with symmetrical PSW metals as microwave electrodes and a dry-transfer process of graphene.The light-graphene interaction is enhanced by utilizing the PSW,resulting a small active detection area of 100 nm×7 μm and a responsivity exceeding 0.13 A/W for the photodetector.Due to the ultra-small size of PSW and the ultra-fast carrier mobility of graphene,the 3-d B bandwidth of the grapheneon-PSW photodetector is exceeded 120 GHz under the theoretical calculation,and the measured bandwidth is greater than 70 GHz.Meanwhile,a high-speed reception of72 Gbit/s signal is realized.(3)Under the direct detection mechanism,the method of increasing the receiving capacity of the graphene-on-PSW photodetector is explored.First,by optimizing the fabrication process of graphene photodetectors,the large-scale production of graphene phtodetectors is realized.Then,using polarization multiplexing technology and combining a focusing two-dimensional grating coupler with dual channels graphene-on-PSW photodetectors,high-quality receptions of 224 Gbit/s four-level pulse-amplitudemodulation signals in a line rate are realized.The active coupling area and detection area of the polarization division multiplexing optical receiver are only 33 μm×45 μm and2×15 μm×100 nm,respectively.(4)Under the coherent detection mechanism,an ultrahigh-speed graphene-PSW optical coherent receiver is proposed to further increase the capacity of the communication system.The scheme combines a 90° optical hybrid and four channels graphene-on-PSW photodetectors to realize an optical coherent receiver with a bandwidth beyond 67 GHz.Using the principle of balanced detection,90 Gbit/s binary phase shift keying signal is received with a promoted signal-to-noise ratio.Moreover,receptions of 200 Gbit/s quadrature phase shift keying and 240 Gbit/s 16 quadrature amplitude modulation signals are realized with the coherent detection.Finally,the inverse-designed method is adopted to reduce the size of the 90° optical hybrid to 4.8 μm×4.2 μm.