Optical Signal Processing Using Silicon-Based Optical Waveguides

With the advent of the high speed information age and the rapid development of optical communication network, one particular trend is that the transmission capacity of optical network link unceasingly obtains the promotion. Therefore it requires high speed and large capacity, tunable, reconstructable, and flexible function for signal processing at the nodes of the network. In addition, the development of optical network need integrated optical devices to reduce the cost and footprint of the system. In the recent research, silicon device has become more and more attractive considering the availability of a mature silicon technology, low costs, nanometer-scale device and compactness and potential for complementary metal-oxide-semiconductor (CMOS) compatibility. In this thesis, optical interconnect, linear and nonlinear signal processing are investigated in silicon devices. The contents of this thesis are as follows:(1) The waveguides structure and nonlinearity are theoretically investigated in the first chapter. ?The wavelength dependence of dispersion and nonlinearity for silicon strip waveguides and silicon slot waveguides are numerically studied. ?The principle of optical signal processing based on nonlinearities of silicon waveguides are discussed. The nonlinear coupled-mode equations are theoretically analyzed, and in which self-phase modulation (SPM), cross-phase modulation (XPM), two-photon absorption (TPA), free-carrier absorption (FCA), degenerate four-wave mixing (D-FWM), and non-degenerate four-wave mixing (ND-FWM) are comprehensively considered.(2) On-chip optical interconnect using silicon waveguides are demonstrated. ? On-chip data transmission performance are analyzed theoretically in both strip waveguide and vertical air slot waveguide. By comparing the strip waveguide and vertical slot waveguide, the influences of nonlinearities on advanced modulation format signal transmission performance are analyzed. ?Ultra-wide bandwidth (Tbit/s) on-chip data transmission are experimentally demonstrated in the silicon vertical slot waveguide utilizing wavelength-division multiplexing (WDM) and 16-ary quadrature amplitude modulation (16-QAM). ?The transmission performance of orthogonal frequency division multiplexing based on offset QAM (OFDM/OQAM) 64-QAM,128/256/512-QAM signals through a silicon microring resonator are investigated experimentally. The influence on optical interconnect transmission by the offset between carrier wavelength and resonant wavelength of silicon microring are also experimentally analyzed. ? Analog transmission link using optical photonic crystal resonator is also experimentally investigated.(3) Linear signal processing based on silicon waveguides are experimentally investigated. ?By using the structural advantage of silicon 2D grating coupler and microring resonators, the (de)multiplexing of polarizations and wavelengths of OFDM/OQAM 64/128-QAM signals is experimentally investigated. ? On-chip multi-mode (de)multiplexer based on silicon waveguides are demonstrated.? An integrated silicon transmitter is designed and fabricated to generate advanced modulation format signals, which is solely based on intensity modulation of the compact microring modulators.(4) Nonlinear signal processing in silicon waveguides is investigated theoretically and experimentally. ?All-optical wavelength conversion of OFDM m-QAM signals based on D-FWM in a silicon waveguide is experimentally investigated, up to 256-QAM signal on chip all-optical wavelength conversion is realized experimentally. ?A simple approach for simultaneous optical half-adder and halfsubtracter based on twin degenerate four-wave mixing processes in a single-slot waveguide is numerically investigated. Two different nonlinear materials Si-nc and PTS are considered as the slot region material for comparison. ?By numerically investigating multiple ND-FWM in silicon-organic slot waveguides, three-input (A, B, C) multicasted 40 GBaud (160-Gbit/s) optical hexadecimal addition/subtraction (A+B-C, A+C-B, B+C-A, A+B+C, A-B-C, B-A-C) are implemented. ?By exploring the high nonlinearity in low and flat dispersion silicon-organic hybrid slot waveguide, modulation-format-transparent ultrahigh-speed optical data exchange for 640 GBaud (2.56 Tbit/s) 16-QAM and 640 GBaud (3.84 Tbit/s) 64-QAM based on the parametric depletion effect of ND-FWM process are investigated. ?By utilizing the XPM process in the same waveguide, high-speed optical hexadecimal coding/decoding of 40 GBaud (160-Gbit/s) 16-QAM signals are investigated. ?An on-chip scalable all-optical signal converter (on-off-keying (OOK) to advanced modulation format signals) are proposed and designed, up to 256-QAM based on XPM in silicon-organic hybrid slot waveguide. ?By controlling the phase in D-FWM of QPSK signal, two-input (A, B) simultaneous 20 Gbit/s optical quaternary hybrid doubling/subtraction (2A-B,2B-A) are experimentally investigated.