Research On Photonic Computing And Information Processing Based On Silicon Micro-Resonators

High-speed multi-functional computing and information processing drive today‘s information age, enabling seamless exchange and interaction between individuals. For commercial computing and information processing systems, the key to reduce the fabrication and development costs is to achieve large-scale integration and standard manufacturing operation. In the past 50 years, the silicon integrated circuits(ICs) have been the mainstay of the electronic information industry and brought revolutionary changes to the world. To date, the maturity and complexity of silicon ICs have been developed to an incredible level. The number of transistors monolithically integrated on a silicon chip with a size of fingernail can reach more than 8 billion, and the computing power is beyond the server that took up a 100-m2 room two decades ago. However, as a result of the continuing of the Moore‘s law and the ever-increasing network capacity, the electronic ICs for computing and information processing are rapidly approaching their fundamental speed limitations, which may not well satisfy the requirements in future ultrahigh-speed scenarios with bandwidths on the order of hundreds of gigahertz or terahertz. In comparison with the electronic counterpart, all-optical computing and information processing based on photonic devices are advantageous in ultrahigh-speed applications by virtue of the superiority in overcoming the bandwidth bottleneck. Moreover, it can also provide competitive advantages of low loss, high flexibility, and strong immunity to electromagnetic interferences. Owing to the rich bandwidth resource in optical domain, photons have the potential to be not only fast ?engines‘ conveying information for ultrafast data transmission, but also sharp ?scissors‘ tailoring signals at a speed far beyond the intrinsic speed limitations to electronics.Under such backgrounds, all-optical computing and information processing based on silicon photonic devices have been merged as an active and fast growing technology. It meets the demands in high-speed applications and relies on the mature CMOS manufacturing technologies, thus possessing features of high speed, low cost, high stability, and large-scale scalability. Among various configurations of silicon photonic devices, microresonators featuring compact footprints, high-Q resonances, wavelength selectivity, and resonance field enhancement find versatile applications in lasers, filters, modulators, switches, routers, delays, detectors and sensors. In this dissertation, we present our research on photonic computing and information processing based on silicon micro-resonators. We first introduce the basic theory and simulation methods of silicon micro-resonators. After that, the fabrication and testing of silicon micro-resonators are discussed. Finally, we propose and experimentally demonstrate photonic computing, microwave photonic signal processing(MPSP), and photonic switching functions based on different prototype silicon micro-resonators. The main research achievements and contributions of this thesis can be summarized as follows:1. Photonic computing based on silicon micro-resonatorsComputing is one of the basic functions of the signal processors. To implement photonic computers with more powerful computing functions and higher computing speed, we propose and experimentally demonstrate three novel schemes for photonic computing based on silicon micro-resonators in this section:1)Tunable first-order photonic differential-equation solver based on a silicon microring resonator(MRR) with two interferometric couplers: The proposed device is capable of solving differential equations characterizing general linear time-invariant(LTI) systems. The operation principle is analyzed, and system testing of solving differential equation with two tunable coefficients is carried out for 10-Gb/s optical Gaussian pulses. The experimental results are in good agreement with theoretical predictions. 2)Tunable second-order photonic differential-equation solver based on a silicon self-coupled microresonator(SCMR): The proposed device provides simplified device configuration and avoids precise wavelength alignment and unequal thermal wavelength drifts as in the case of cascaded resonators. System demonstration is performed using 10-Gb/s optical Gaussian and super-Gaussian input pulses, and the experimental results verify the effectiveness of the fabricated device as a tunable second photonic differential-equation solver. 3)High-speed high-order photonic differentiator based on a silicon self-coupled optical-waveguide(SCOW) microresonator: We propose and demonstrate the first on-chip fourth-order photonic differentiator implemented by a silicon four-stage SCOW microresonator. Fourth-order differentiation of ultrahigh-speed picosecond pulse signal at a record high processing speed is experimentally achieved.2. MPSP based on silicon micro-resonatorsMicrowave signal processing plays an important role and finds wide applications in modern military and communication systems. To achieve improved flexibility and performances of MPSP, we propose and experimentally demonstrate four typical MPSP functions using silicon micro-resonators in this section:1) Tunable microwave photonic notch filter based on a silicon SCMR: A continuously tunable microwave photonic notch filter using the through port of the SCMR is proposed and experimentally demonstrated for the first time. A high rejection ratio over 25 d B and a wide tuning range over 20 GHz is achieved in our experiment. 2) Photonic generation of millimeter-wave(MMW) signal based on a silicon SCMR: Photonic MMW generation base on frequency extracting using the drop port of the SCMR is proposed and experimentally demonstrated for the first time. In the experiment, we have demonstrated photonic generation of ~39-GHz and ~29-GHz MMW signals using the fabricated devices. 3) Tunable photonic radio-frequency(RF) phase shifter based on a microdisk resonator(MDR): A tunable photonic RF phase shifter based on a single MDR is proposed and experimentally demonstrated for the first time. Benefitting from the high Q factor of the MDR, an increased phase-shift tuning range of 6.1 rad that approaches 2π has been achieved in our experiment, which is improved by ~30% in comparison with those of reported photonic RF phase shifters based on a single resonator. 4) Optical delay line(ODL) based on a nested silicon microring resonator(NMRR): We propose and experimentally demonstrate an ODL implemented by a passive silicon NMRR with various group delay values at different resonance wavelengths. System measurement of pulse delay values at different resonance notches is carried out for 5-Gb/s optical Gaussian pulses. The proposed device could provide diverse pulse delays with reduced complexity and fabrication cost.3. Photonic switching based on silicon micro-resonatorsEver-increasing network capacity and efficiency are driving the demand for high-performance photonic switching in optical communication networks. To improve the performance of photonic switching, we propose and experimentally demonstrate two novel photonic switching components based on silicon micro-resonators in this section:1) 2×2 non-blocking switching unit based on a pair of silicon NMRR: We propose and experimentally demonstrate a 2×2 optical Benes switching unit based on a pair of silicon NMRRs. High extinction ratios(ERs) of ~44.7 / 38.0 d B and low crosstalk values of ~-37.5 /-45.2 d B at cross / bar states are obtained with the fabricated device. The operation principle is theoretically studied, and the switching function is verified by system experiments with 10 Gb/s and 12.5 Gb/s NRZ signals. 2) 1 × 2 wavelength selective switches(WSSs) based on silicon MRR with nested pairs of subrings(NPSs): The proposed devices possess more compact footprints due to an effective utilization of the area inside the resonant loops. The selective manipulation of equally-spaced resonance notches/peaks of the same MRR also avoids precise tuning of wavelength channels from different MRRs. System demonstration of dynamic channel routing using fabricated devices with one and two NPSs are carried out for 10-Gb/s NRZ signal, which verify the feasibility of the proposed scheme.