"Silicon photonics is the most promising candidate to achieve the high data transmission rates required for future telecommunications bandwidth demands, which require upgraded optical interconnects. Optical modulators, such as Mach-Zehnder modulators, are one of the most important sub-components in any optical communication system. Leveraging the complementary metal-oxide semiconductor (CMOS) fabrication processes, the integration of optical devices become more cost effective and energy efficient. Optical frequency comb has widespread applications in microwave photonics and optical communications as a multi-wavelength source for wavelength division multiplexing and orthogonal frequency division multiplexing systems. The most common approach to generate optical frequency comb is based on the use of optical modulators. On-chip optical frequency comb generation has great flexibility to tune the center frequency based on the frequency of the continuous wave laser, comb spacing, and the number of comb lines based on adjusting the RF signal frequency, power, and phase that is applied to the electro-optic modulator. The limitation of this technique lies in the high insertion loss, especially in cascaded modulators. In this thesis, we investigate two integrated cascaded electro-optic modulators in CMOS-compatible silicon-on-insulator for optical frequency comb generation. The first comprises cascaded push-pull traveling wave Mach-Zehnder modulators (MZM) while the second involves cascaded microring modulators (MRM). The 9 comb lines with a spacing up to 10 GHz and bandwidth of 90 GHz for the cascaded MZM, and 5 comb lines with a spacing up to 10 GHz and a bandwidth of 50 GHz for the cascaded MRM. The measured temporal waveforms corresponding to the generated quasi-rectangular combs match with the sinc-shaped Nyquist pulses which are well-known for its high spectral efficiency and have zero inter-symbol interference. Lastly, we summarize and compare the performance of both modulators"--

SOH (silicon-organic hybrid) elektrooptische Modulatoren kombinieren Siliziumphotonik mit organischen elektro-optischen Materialien. Dieses Buch befasst sich mit Aspekten, die speziell für den Einsatz von SOH-Modulatoren in praktischen optischen Hochgeschwindigkeitskommunikationssystemen relevant sind, wie z. B. Aufbau- und Verbindungstechnik, Modellierung und die Implementierung effizienter Modulationsformate für IM/DD-Formate. - Silicon-organic hybrid (SOH) electro-optic modulators combining silicon photonic structures with organic EO materials are investigated. This book addresses aspects that are specifically relevant for the use of SOH modulators in practical high-speed optical communication systems such as packaging, modelling of the device, and the implementation of efficient intensity-modulation/direct-detection (IM/DD) modulation formats.

Silicon-organic hybrid (SOH) modulators add a highly efficient nonlinear organic electro-optic cladding material to the silicon photonic platform, thereby enabling efficient electro-optic modulation. In this book, the application potential of SOH modulators is investigated. Proof-of-principle experiments show that they can be used for high-speed communications at symbol rates up to 100 GBd and operated directly from a field-programmable gate array (FPGA) without additional driver amplifiers.

In this book, silicon photonic integrated circuits are combined with electro-optic organic materials for realizing energy-efficient modulators with unprecedented performance. These silicon-organic hybrid Mach-Zehnder modulators feature a compact size, sub-Volt drive voltages, and they support data rates up to 84 Gbit/s. In addition, a wet chemical waveguide fabrication scheme and an efficient fiber-chip coupling scheme are presented.

"In recent years, the amount of traffic within data centers has increased to a point where electrical interconnects are being replaced by optical interconnects and pluggable modules. Silicon photonics, which uses the existing CMOS fabrication capabilities to develop integrated photonics, offers the ability to make compact devices in high volume with relatively better yield. This makes it a highly desired platform to develop optical transceivers and components for modern data centers. As such, it has recently reached the production phase of the technology development cycle. This thesis studies several devices that are applicablein leading data centers. A detailed analysis and characterization of a silicon Michelson modulator with short 500 um phase shifters and a low VpiLpi of 0.72 V-cm under reverse bias is presented. The optical modulation of reverse biased p-n and forward biased p-i-n junctions is investigated. For reverse bias operation, it is demonstrated that bandwidth can be increased with lower impedance drivers and the driver impedance limits the bitrate achievable. Furthermore, forward bias operation with pre-emphasized signals is shown to have clean eye diagrams up to 40 Gbps. Energy consumption is estimated for all cases of studies and their trade-offs are explained.The work on modulators is further developed by studying series push-pull traveling wave Mach-Zehnder modulators. Measurements of electrodes is compared with simulation validating the methods of increasing impedance and microwave effective index with T-shaped electrodes. Moreover, designs with two and three level implants are compared and it is concluded with measurements that a two level doping design is as good as the design with three level implants, thus reducing the number of masks and processing steps required. Another variation of modulators is the dual-drive modulators. Here, the spacing between electrodes can lead to coupling, which results in different responses depending on whether the modulator is driven single-endedly or differentially. The electro-optic frequency response of a four-port traveling-wave dual-drive modulator with relatively weak coupling amongst the electrodes is measured. It is shown that the electro-optic frequency response of the Mach-Zehnder modulator can be predicted with a 2x2 cascaded matrix model if the Mach-Zehnder modulator is symmetric and differentially driven. In recent years, the increase in data transfers has demanded that more bits be transmitted and received in a given bandwidth. The design and characterization of a silicon-on-insulator traveling-wave multi-electrode Mach-Zehnder modulator is reported in this thesis. This 2-bit electro-optic digital-to-analog converter is formed by dividing a series push-pull Mach-Zehnder modulator into two segments, one for each bit, thus allowing for PAM-4 modulation without using a digital-to-analog converter. The device is operated at speeds up to 50 Gbaud and thus generating 100 Gbps on a single wavelength without signal processing at the transmitter or the receiver. The pre-forward error correction bit error rate is estimated to be lower than the hard-decision forward error correction threshold of 3.8e-3 over 1 km of standard single-mode fiber.Another component that is crucial in optical networks is the optical switch. The optical switch has numerous applications in protection and restoration as well as in certain modern data center architectures. A 4x4 fully non-blocking crossbar switch fabric based on interferometric thermal phase shifters is developed and reported in this thesis. Here, heating is achieved using resistive elements around the silicon waveguide. Switching times of 5 us and 36 mW power consumption in an individual switching element is measured. As a proof of concept, the quality in degradation of switching is demonstrated by routing an input signal to some of the outputs of the switch." --

Silicon photonics is beginning to play an important role in driving innovations in communication and computation for an increasing number of applications, from health care and biomedical sensors to autonomous driving, datacenter networking, and security. In recent years, there has been a significant amount of effort in industry and academia to innovate, design, develop, analyze, optimize, and fabricate systems employing silicon photonics, shaping the future of not only Datacom and telecom technology but also high-performance computing and emerging computing paradigms, such as optical computing and artificial intelligence. Different from existing books in this area, Silicon Photonics for High-Performance Computing and Beyond presents a comprehensive overview of the current state-of-the-art technology and research achievements in applying silicon photonics for communication and computation. It focuses on various design, development, and integration challenges, reviews the latest advances spanning materials, devices, circuits, systems, and applications. Technical topics discussed in the book include: • Requirements and the latest advances in high-performance computing systems • Device- and system-level challenges and latest improvements to deploy silicon photonics in computing systems • Novel design solutions and design automation techniques for silicon photonic integrated circuits • Novel materials, devices, and photonic integrated circuits on silicon • Emerging computing technologies and applications based on silicon photonics Silicon Photonics for High-Performance Computing and Beyond presents a compilation of 19 outstanding contributions from academic and industry pioneers in the field. The selected contributions present insightful discussions and innovative approaches to understand current and future bottlenecks in high-performance computing systems and traditional computing platforms, and the promise of silicon photonics to address those challenges. It is ideal for researchers and engineers working in the photonics, electrical, and computer engineering industries as well as academic researchers and graduate students (M.S. and Ph.D.) in computer science and engineering, electronic and electrical engineering, applied physics, photonics, and optics.