Processing of high-speed data using optical signals is a promising approach for tackling the bandwidth and speed challenges of today's electronics. Realization of complex optical signal processing functionalities seems more possible than any time before, thanks to the recent achievements in silicon photonics towards large-scale photonic integration. In this Ph. D. work, a novel thermal reconfiguration technology is proposed and experimentally demonstrated for silicon photonics that is compact, low-loss, low-power, fast, with a large tuning-range. These properties are all required for large-scale optical signal processing and had not been simultaneously achieved in a single device technology prior to this work. This device technology is applied to a new class of resonator-based devices for reconfigurable nonlinear optical signal processing. For the first time, we have demonstrated the possibility of resonance wavelength tuning of individual resonances and their coupling coefficients. Using this new device concept, we have demonstrated tunable wavelength-conversion through four-wave mixing in a resonator-based silicon device for the first time.

Integrated optics as a platform for signal processing offers significant benefits such as large bandwidth, low loss, and a potentially high degree of reconfigurability. Silicon (Si) has unique advantages as a material platform for integration, as well as properties such as a strong thermo-optic mechanism that allows for the realization of highly reconfigurable photonic systems. Chapter 1 is devoted to the discussion of these advantages, and Chapter 2 provides the theoretical background for the analysis of integrated Si-photonic devices. The thermo-optic property of Si, while proving extremely useful in facilitating reconfiguration, can turn into a nuisance when there is a need for thermally stable devices on the photonic chip. Chapter 3 presents a technique for resolving this issue without relying on a dynamic temperature stabilization process. Temperature-insensitive (or "athermal") Si microdisk resonators with low optical loss are realized by using a polymer overlayer whose thermo-optic property is opposite to that of Si, and TiO2 is introduced as an alternative to polymer to deal with potential CMOS-compatibility issues. Chapter 4 demonstrates an ultra-compact, low-loss, fully reconfigurable, and high-finesse integrated photonic filter implemented on a Si chip, which can be used for RF-photonic as well as purely optical signal processing purposes. A novel, thermally reconfigurable reflection suppressor is presented in Chapter 5 for on-chip feedback elimination which can be critical for mitigating spurious interferences and protecting lasers from disturbance. Chapter 6 demonstrates a novel device for on-chip control of optical fiber polarization. Chapter 7 deals with select issues in the implementation of Si integrated photonic circuits. Chapter 8 concludes the dissertation.

This hands-on introduction to silicon photonics engineering equips students with everything they need to begin creating foundry-ready designs.

Development of the computing platform of the future depends largely on high bandwidth interconnects at intra-die level. Silicon photonics, as an innately CMOS compatible technology, is a promising candidate for delivering terabit per second bandwidths through the use of wavelength division multiplex (WDM) signaling. Silicon photonic interconnects offer unmatched bandwidth, density, energy efficiency, latency and reach, compared with the electrical interconnects. WDM silicon photonic links are viewed today as a promising solution for resolving the inter/intra-chip communication bottlenecks for high performance computing systems. Towards its maturity, silicon photonic technology has to resolve the issues of waveguide propagation loss, density of device integration, thermal stability of resonant devices, heterogeneous integration of various materials and many other problems. This dissertation describes the development of integrated photonic technology on silicon and silicon nitride platforms in the increased order of device complexity, from the fabrication process of low loss waveguides and efficient off-chip coupling devices, to the die-size reconfigurable lattice filters for optical signal processing. Particular emphasis of the dissertation is on the demonstration of CMOS-compatible, athermal silicon ring modulators that potentially hold the key to solving the thermal problem of silicon photonic devices. The development of high quality amorphous titanium dioxide films with negative thermo-optic coefficient enabled the fabrication of gigahertz-bandwidth silicon ring modulators that can be made insensitive to ambient temperature changes.

Among the various elements of the silicon photonics platform, electro-optic IQ modulators play an important role. In this book, silicon-organic hybrid (SOH) integration is used to realize electro-optic IQ modulators for complex signal processing. Leveraging the high nonlinearity of organic materials, SOH IQ modulators provide low energy consumption for high-speed data transmission and frequency shifting. Furthermore, the device design is adapted for commercial foundry processes.

This book provides the first comprehensive, up-to-date and self-contained introduction to the emergent field of Programmable Integrated Photonics (PIP). It covers both theoretical and practical aspects, ranging from basic technologies and the building of photonic component blocks, to design alternatives and principles of complex programmable photonic circuits, their limiting factors, techniques for characterization and performance monitoring/control, and their salient applications both in the classical as well as in the quantum information fields. The book concentrates and focuses mainly on the distinctive features of programmable photonics, as compared to more traditional ASPIC approaches. After some years during which the Application Specific Photonic Integrated Circuit (ASPIC) paradigm completely dominated the field of integrated optics, there has been an increasing interest in PIP. The rising interest in PIP is justified by the surge in a number of emerging applications that call for true flexibility and reconfigurability, as well as low-cost, compact, and low-power consuming devices. Programmable Integrated Photonics is a new paradigm that aims at designing common integrated optical hardware configurations, which by suitable programming, can implement a variety of functionalities. These in turn can be exploited as basic operations in many application fields. Programmability enables, by means of external control signals, both chip reconfiguration for multifunction operation, as well as chip stabilization against non-ideal operations due to fluctuations in environmental conditions and fabrication errors. Programming also allows for the activation of parts of the chip, which are not essential for the implementation of a given functionality, but can be of help in reducing noise levels through the diversion of undesired reflections.

High-speed electro-optic modulators in silicon platform are introduced and experimentally verified. The devices rely on plasmonic and photonic slot waveguides and are combined with efficient organic electro-optic materials. The bandwidth limitation of conventional silicon-organic-hybrid modulators is circumvented by capacitive coupling of the microwave signal. An advanced terahertz link that upconverts data directly from a 360 GHz carrier to an optical carrier is demonstrated for the first time.

Photonic signal processing has been considered a promising solution to overcome the inherent bandwidth limitations of its electronic counterparts. Over the last few years, an impressive range of photonic integrated signal processors have been proposed with the technological advances of III-V and silicon photonics, but the signal processors offer limited tunability or reconfigurability, a feature highly needed for the implementation of programmable photonic signal processors. In this thesis, tunable and reconfigurable photonic signal processors are studied. Specifically, a photonic signal processor based on the III-V material system having a single ring resonator structure for temporal integration and Hilbert transformation with a tunable fractional order and tunable operation wavelength is proposed and experimentally demonstrated. The temporal integrator has an integration time of 6331 ps, which is an order of magnitude longer than that provided by the previously reported photonic integrators. The processor can also provide a continuously tunable fractional order and a tunable operation wavelength. To enable general-purpose signal processing, a reconfigurable photonic signal processor based on the III-V material system having a three-coupled ring resonator structure is proposed and experimentally demonstrated. The reconfigurability of the processor is achieved by forward or reverse biasing the semiconductor optical amplifiers (SOAs) in the ring resonators, to change the optical geometry of the processor which allows the processor to perform different photonic signal processing functions including temporal integration, temporal differentiation, and Hilbert transformation. The integration time of the signal processor is measured to be 10.9 ns, which is largely improved compared with the single ring resonator structure due to a higher Q-factor. In addition, 1st, 2nd, and 3rd of temporal integration operations are demonstrated, as well as a continuously tunable order for differentiation and Hilbert transformation. The tuning range of the operation wavelength is 0.22 nm for the processor to perform the three functions. Compared with the III-V material system, the CMOS compatible SOI material system is more cost effective, and it offers a smaller footprint due to the strong refractive index contrast between silicon and silica. Active components such as phase modulators (PMs) can also be implemented. In this thesis, two photonic temporal differentiators having an interferometer structure to achieve active and passive fractional order tuning are proposed and experimentally demonstrated. For both the active and passive temporal differentiators, the fractional order can be tuned from 0 to 1. For the active temporal differentiator, the tuning range of the operation wavelength is 0.74 nm. The use of the actively tunable temporal differentiator to perform high speed coding with a data rate of 16 Gbps is also experimentally demonstrated.

The incredible growth of the network capacity requires bandwidth-scalable and high-fidelity optical waveform generation, detection and manipulation. However, large bandwidth waveform generation and detection with high-fidelity are challenging because the direct modulation and detection scheme using electrical components cannot go beyond 100 GHz. Bandwidth-scalable transceivers can overcome this bottleneck by using parallel optical spectral-slices. Besides, photonic-integrated-circuit (PIC) based optical signal processing components that support either single mode or multimode signal operations enable low-latency and low-cost waveform manipulation. This dissertation focuses on developing optical signal processing transmitters and receivers using parallel optical spectral-slices, and on implementing optical signal processing components such as silicon photonic lattice filters, three-dimensional waveguide based multimode multiplexers. On the transmitter side, we ease the processing load on the electrical digital-to-analog converters by using optical frequency multiplexing technology and by modulating each spectral slices with narrow-bandwidth electrical modulators. Not only that, but the spectrally-sliced transmitter is bandwidth-scalable and can provide full control of the waveform that facilitates flexible bandwidth management. The thesis also introduces a complete waveform shaping algorithm that can help with high-fidelity waveform generation. On the receiver side, the architecture is symmetric to that of the spectrally-sliced transmitter. The optical demultiplexing technology allows us to detect each narrow-bandwidth spectral slice, and then to reconstruct the full waveform by off-line digital signal processing. On the signal processing components side, we demonstrate a silicon photonic reconfigurable lattice filter that uses identical unit cell structures to implement complex transfer functions. We have also developed a filter synthesis algorithm to fully control the phase shifters of the optical lattice filter. Besides single mode components, we have come up with a novel three-dimensional waveguide writing technique with femtosecond laser writing and have shown 3D waveguide based space-division multiplexers for orbital-angular-momentum (OAM) modes and linearly polarized (LP) modes. Experimental results include two spectral-slices based 60-GBd QPSK and 16-QAM waveform generations, 228-GHz QPSK waveform measurements after up to 3,200-km transmission, a bandpass filter with 600-MHz 3-dB bandwidth, a hybrid PIC device that multiplexes up to 15 OAM states and a 3D waveguide based photonic lantern that multiplexes 15 spatial modes (LP modes). We believe that optical signal processing systems and components can satisfy demands of network capacity increases. With the support of advanced photonic integration, optical signal processing plays an important role in the future optical fiber communication systems.

The open access journal Micromachines invites manuscript submissions for the Special Issue “Silicon Photonics Bloom”. The past two decades have witnessed a tremendous growth of silicon photonics. Lab-scale research on simple passive component designs is now being expanded by on-chip hybrid systems architectures. With the recent injection of government and private funding, we are living the 1980s of the electronic industry, when the first merchant foundries were established. Soon, we will see more and more merchant foundries proposing well-established electronic design tools, product development kits, and mature component libraries. The open access journal Micromachines invites the submission of manuscripts in the developing area of silicon photonics. The goal of this Special Issue is to highlight the recent developments in this cutting-edge technology.]