[PDF] High Performance Photonic Analog To Digital Converter And Low Noise Mode Locked Fiber Lasers eBook
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This project demonstrates three photonic analog-digital converters (ADCs) for high-speed, real-time digitization of microwave signals. The methods consist of a highly parallel photonic ADC, a time-division multiplexed system based on electro-optical Sagnac interferometry, and an alloptical quantizer based upon distributed phase modulation. The core of many photonic ADC designs relies upon a low-noise, actively modelocked fiber laser that has been developed at NRL. Photonic sampling of microwave signals is investigated especially concerning development of a low-noise optical clock. Optimization and system post-processing is simulated and compared with experimental data. Finally, the low-noise optical clock was used in a four-way collaborative research effort where NRL excited and characterized high-speed, high-current photoconductive switches.
Modulating the saturable absorber provides a reduced third-order intermodulation tone with respect to modulating the gain. This is simply because of the unwanted amplitude modulation created when modulating the gain section current. Finally an improved design is proposed and demonstrated to improve the modulator performance. This is achieved by introducing a third section to the laser. Using the impurity free vacancy disordering technique the photoluminescence peak of this section is blue-shifted selectively and therefore there would not be any absorption in that passive section. By applying the modulation signal to this passive section rather than applying it to the gain section or saturable absorber section, the amplitude and phase modulation could be decoupled. The experimental results have presented here and an almost six-fold reduction in V[subscript pi] and 5 dB improvement in spur free dynamic range have been achieved. The proposed and demonstrated configuration as an analog optical link has the potential to increase the performance and resolution of photonic analog-to-digital converters.
High-speed, broadband, and compact analog-to-digital converters (ADC) are the key components in signal waveform generation and efficient detection for future telecommunication and remote sensing applications. Canonical electronic ADCs suffers from limited effective number of bits (ENOB) at giga-sampling rate due to electronic clock aperture jitter and comparator ambiguity due to the transistor bandwidth limitations. An electrically interleaved ADC operating at lower sampling rates or a hybrid ADC using optically sampled and electrically quantized structures that leverages the low optical aperture jitter of mode-locked laser and high-resolution electronic quantization are not only power consuming but are also limited in effective sampling rate within 10 GS/s as the quantizer outputs still must be accurately aligned in time to form the input information in electronic domain. On the other hand, the reported all-optical ADC (AOADC) benefits from the low jitter of optical clock, while quantizes the input signal in optical domain using spatial modulation. In this dissertation, various design innovations leading to paths of a fully integrated 40 GS/s AOADC with 8 ENOB by incorporating integrated stable clock using self-forced optical phase modulator (PM) based opto-electronic oscillators (OEO) and single-channel spatial light modulator (SLM) by advancing research innovations of the past laboratory graduates.Design of optical PM and SLM designs are based on broadband traveling-wave coupled microstrip (CMS) electrode structures with improved phase and angular deflection modulation using slow-waveguiding behavior of 1-D photonic crystal (PhC) topologies as superstrate using optical beam propagation (OptiBPM), finite-difference-time-domain (OptiFDTD), and finite element method (HFSS). Optimized design geometries of 1-D PhC over 1550 nm is considered to minimize the optical loss while the modulation sensitivity is enhanced by about 108% compared to modulator designs without the PhC layer. Similar spatial modulation sensitivity improvements are achieved for SLMs with leaky wave designs. These designs are implemented on low-cost Si-photonics and electro-optic (E-O) chromophores on low loss and higher index PMMI host material rather than standard PMMA. Novel design of OEO based on PM rather than Mach-Zehnder modulator (MZM) has advantage of bias voltage independence that makes OEO less sensitive to shift in bias voltage due to piezo-electric or pyro-electric properties of E-O material, but then requires phase to intensity modulators (PM-IM). Sagnac-loop based OEO is demonstrated, where close-in to carrier phase noise at 10 GHz are reduced using self-forced techniques of self-injection locking and dual self-phase-locked loop (SILDPLL) for long-term stability of optical clocks to predict timing jitter as low as 19.5 fs using 3-/5-km fiber mandrills in modular experiment.To achieve a monolithically integrated AOADC consisting of the proposed SLM and stable optical clock provided by OEOs with the estimated performance, a heterogeneously integrated InP multi-mode laser (MML) as an on-chip OEO source, where inter-modal oscillation and PM-IM convertor rather than relying on Sagnac-loop design, where a non-reciprocal phase shifter (NRPS) is not compatible with Si on-chip integration at the present. RF signal generated from MML typically suffers poor stabilization and 25-fold reduction in timing jitter is measured compared to the free-running case, when SEILDPLL with external optical delays of 5-/15-(mu)s are employed. Moreover, for a fully integrated design rather than modular fiber mandrills, both non-dispersive and dispersive add-drop filter (ADF) resonators are modeled using both full-wave OptiFDTD and proven MATLAB codes on SiN based optical time delays of 975 ns within a chip area of 27 cm2 and 0.1 cm2, respectively. Furthermore, limits of performance improvements using a combined stabilization processes of self-mode-locking (SML) techniques and self-forced SML are investigated. Timing jitter of a 13-mode SML (e.g., fabricated using HHI foundry service) with 700 ns SEIL and 700-/900-ns DSPLL integrated IOEO is estimated to be only 7.6 fs at 10 GHz.
Provides a comprehensive look at the application of photonic approaches to the problem of analog-to-digital conversion. It looks into the progress made to date, discusses present research, and presents a glimpse of potential future technologies.
Throughout history, light has been a valuable communication tool, and today it is revolutionizing information exchange. From optical networks and amplifiers to broadband lasers and detectors, the 1999 Optical Fiber Communication Conference (OFC), collocated with the International Conference on Integrated Optics and Optical Fiber Communication (IOOC), presents the latest advances in this rapidly growing field.
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.
Mayo has collaborated with AFRL on the study of an optical to electrical architecture for a high performance photonic- based analog-to-digital converter. This document summarizes the work comprising this study and the resulting conclusions.