"Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. Thanks to the existing CMOS technology, silicon photonics have attracted worldwide attention with the advantage of easy fabrication,low cost, seamless integration with electronics and so on. Many passive and active silicon photonic devices as well as integrated system with high performance are designed and fabricated. The work presented in this thesis are several devices using the silicon photonic platform to realize different applications in optical communication systems. Firstly, a passive integrated nonlinear optical loop mirror is reported. The theoretical study and device design are described and its applications in all-optical signal processing, such as wavelength conversion, NRZ-to-RZ modulation formatconversion, OADM demultiplexing, are demonstrated. A novel picosecond pulse width measurement method based on nonlinear optical loop mirror is presented as well. Secondly, we provide an optical frequency comb generator based on two cascaded push-pull Mach-Zehnder modulators. Nine phase-locked frequency combs with bandwidth up to 54 GHz are generated and the signal-to-noise ratio is around 40 dB after optical amplification and filtering. Furthermore, an integrated OADM device based on mode selection and Bragg grating structure is demonstrated. The theoretical and experimental study of the device is provided and the performance of spectral response, crosstalk and BER measurement is reported. At last, silicon-based superstructure gratings are studied. The fixed and thermally tunable superstructure gratings are presented. We discuss the influence of different parameters like corrugation depth, sampling duty cycle, sampling period and polarization on the reflection features of fixed superstructure gratings both in theory and experiment. We also realize a thermally tunable optical filter based on the periodic heating of a uniform Bragg grating. We believe the devices and techniques described in this thesis, along with others in silicon photonics point to the feasibility of more complex integrated optical communication systems with increased functionality and performance"--

"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"--

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.

Nonlinear photonics is the name given to the use of nonlinear optical devices for the generation, communication, processing, or analysis of information. This book is a progress report on research into practical applications of such devices. At present, modulation, switching, routing, decision-making, and detection in photonic systems are all done with electronics and linear optoelectronic devices. However, this may soon change, as nonlinear optical devices, e.g. picosecond samplers and switches, begin to complement optoelectonic devices. The authors succinctly summarize past accomplishments in this field and point to hopes for the future, making this an ideal book for newcomers or seasoned researchers wanting to design and perfect nonlinear optical devices and to identify applications in photonic systems.

This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was "1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, b) frequency skewed pulse generation for ranging and c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work.

Over the last few years, there has been a convergence between the fields of ultrafast science, nonlinear optics, optical frequency metrology, and precision laser spectroscopy. These fields have been developing largely independently since the birth of the laser, reaching remarkable levels of performance. On the ultrafast frontier, pulses of only a few cycles long have been produced, while in optical spectroscopy, the precision and resolution have reached one part in Although these two achievements appear to be completely disconnected, advances in nonlinear optics provided the essential link between them. The resulting convergence has enabled unprecedented advances in the control of the electric field of the pulses produced by femtosecond mode-locked lasers. The corresponding spectrum consists of a comb of sharp spectral lines with well-defined frequencies. These new techniques and capabilities are generally known as “femtosecond comb technology. ” They have had dramatic impact on the diverse fields of precision measurement and extreme nonlinear optical physics. The historical background for these developments is provided in the Foreword by two of the pioneers of laser spectroscopy, John Hall and Theodor Hänsch. Indeed the developments described in this book were foreshadowed by Hänsch’s early work in the 1970s when he used picosecond pulses to demonstrate the connection between the time and frequency domains in laser spectroscopy. This work complemented the advances in precision laser stabilization developed by Hall.

The emerging field of silicon photonics allows us to develop more efficient networks that go beyond the capabilities and limitations of current electronic networks. Integrated photonic solutions in the present and in the future will allow us to keep pace with Moore's Law. Expertise in Silicon fabrication is at a very advanced level due to its use in semiconductor electronics. This expertise can be applied directly to fabricating optical devices using silicon as a medium of propagation for light. Silicon shows a high non linear optical response with high intensities. The high intensities required to see non linearity can be achieved by using waveguides etched into the silicon which confine light to a small mode area thus increasing intensity. One application for silicon waveguide devices is the development of frequency combs. A frequency comb can act as an accurate frequency standard over a very large bandwidth that can range from the visible all the way through to the Mid IR. Applications for frequency combs can be found in high precision spectroscopy, optical metrology, highly precise optical atomic clocks and so on. By the very nature of its frequency spectrum, we expect to see short pulses in the temporal domain from a frequency comb. This thesis examines the building of an autocorrelation setup that can measure these pulses to high accuracy. We explore the choice of detection scheme, the choice of setup and go on to discuss some results from the setup that was built as part of the work leading up to this date.

This book provides a comprehensive review of the state-of-the art of optical signal processing technologies and devices. It presents breakthrough solutions for enabling a pervasive use of optics in data communication and signal storage applications. It presents presents optical signal processing as solution to overcome the capacity crunch in communication networks. The book content ranges from the development of innovative materials and devices, such as graphene and slow light structures, to the use of nonlinear optics for secure quantum information processing and overcoming the classical Shannon limit on channel capacity and microwave signal processing. Although it holds the promise for a substantial speed improvement, today’s communication infrastructure optics remains largely confined to the signal transport layer, as it lags behind electronics as far as signal processing is concerned. This situation will change in the near future as the tremendous growth of data traffic requires energy efficient and fully transparent all-optical networks. The book is written by leaders in the field.

Recently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth from the mode-locked laser, it is critical to know the free spectral range (FSR) of the etalon precisely. First the etalon FSR is measured by using the modified Pound-Drever-Hall (PDH) based method and obtained a resolution of 1 part in 106, which is 2 order of magnitude better than the standard PDH based method. After optimizing the cavity length, RF driving frequency and PDH cavity locking point, the mode-locked laser had an integrated timing jitter of 3 fs (1 Hz- 100 MHz) which is, to the best of our knowledge, the lowest jitter ever reported from a semiconductor based multigigahertz comb source. The mode-locked laser produces ~ 100 comb lines with 10 GHz spacing, a linewidth of ~500 Hz and 75 dB optical signal-to-noise ratio. The same system can also be driven as a regeneratively mode-locked laser with greatly improved noise performance. Another way of generating a low noise RF tone is using an opto-electronic oscillator which uses an optical cavity as a high Q element. Due to the harmonic nature of OEOs, a mode selection element is necessary. Standard OEOs use an RF filter having drawbacks such as broad pass band, high loss, and high thermal noise. In our work, a novel optoelectronic scheme which uses an optical filter (Fabry-Perot etalon) as the mode filter instead of an RF filter is demonstrated. This method has the advantage of having ultra-narrow filtering bandwidths (~ 10 kHz for a 10 GHz FSR and 106 finesse) and an extremely low noise RF signal. Experimental demonstration of the proposed method resulted in a 5-10 dB decrease of the OEO noise compared to the conventional OEO setup. Also, by modifying the etalon-based OEO, and using single side band modulation, an optically tunable optoelectronic oscillator is achieved with 10-20 dB lower noise than dual side band modulation. Noise properties of the OEO as a function of optical frequency detuning is also analyzed theoretically and the results are in agreement with experimental results. The thesis concludes with comments on future work and directions.