The construction and characterization of ultra-low noise semiconductor-based mode-locked lasers as frequency comb sources with multi-gigahertz combline-to-combline spacing is studied in this dissertation. Several different systems were built and characterized. The first of these systems includes a novel mode-locking mechanism based on phase modulation and periodic spectral filtering. This mode-locked laser design uses the same intra-cavity elements for both mode-locking and frequency stabilization to an intra-cavity, 1,000 Finesse, Fabry-Pérot Etalon (FPE). On a separate effort, a mode-locked laser based on a Slab-Coupled Optical Waveguide Amplifier (SCOWA) was built. This system generates a pulse-train with residual timing jitter of

An approach to integrated frequency-comb filtering is presented, building from a background in photonic crystal cavity design and fabrication. Previous work in the development of quantum information processing devices through integrated photonic crystals consists of photonic band gap engineering and methods of on-chip photon transfer. This work leads directly to research into coupled-resonator optical waveguides which stands as a basis for the primary line of investigation. These coupled cavity systems offer the designer slow light propagation which increases photon lifetime, reduces size limitations toward on-chip integration, and offers enhanced light-matter interaction. A unique resonant structure explained by various numerical models enables comb-like resonant clusters in systems that otherwise have no such regular resonant landscape (e.g. photonic crystal cavities). Through design, simulation, fabrication and test, the work presented here is a thorough validation for the future potential of coupled-resonator filters in frequency comb laser sources.

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.

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An optical frequency comb is a structure of equidistant, coherent spectral components which can be thought of as a large array of individual phase-locked laser sources. Their utilization in precision spectroscopy garnering part of the 2005 Nobel prize, optical frequency combs constitute a relatively novel technology with a large number of potential and actual applications. The research interest grew further with the 2007 discovery of comb structures in microresonators enclosing a nonlinear Kerr medium pumped by an external continuous wave laser, offering both substantially wider combs and the prospect of chip-scale integration. In this thesis work, the modeling of frequency comb spectra generated through optical Kerr cavities is considered using both an Ikeda map and the mean-field Lugiato-Lefever equation to describe the intracavity field evolution. Derivations of these mathematical models are first reviewed alongside relevant physics. They are then treated analytically to constrain model parameters to regions of interest in the context of Kerr-comb dynamics. Finally, numerical parameter sweeps are conducted in both models with respect to the pump power and frequency detuning, where the Ikeda map is additionally examined in the high-energy regime not faithfully described by the Lugiato-Lefever equation. The produced phase diagrams reveal a complex landscape of dynamics including Turing patterns, temporal cavity solitons, breathers and chaos. Ikeda map parameters in the high-energy regime capable of supporting previously reported super energetic cavity solitons are also investigated. Lastly, the numerical simulation package developed for parameter sweeps is presented.

<p>Evolutionary innovations, at the molecular level, represent the novel establishment of regulation networks among previously unconnected genes. Understanding the cellular and molecular mechanisms that underlies the development of such innovations is of central importance in evolutionary-developmental research (evo-devo). The sex comb of <em>Drosophila</em> is an excellent model to study the molecular basis of evolutionary innovations. Highline and Lowline are two artificial selected <em>D. melanogaster</em> lines differing in the number of sex comb bristles. It was expected that the “cross-regulation loop” between two transcription factors, <em>Doublesex</em> male isoform (DSX^M) and <em>Sexcombs reduced</em> (SCR), evolves rapidly and promotes the morphological evolution of sex combs. We used immunofluorescent technique (antibody staining) to compare the expression of DSX^M and SCR in the forelegs of three different lines (Highline, Wildtype and Lowline). We hypothesized that artificial selection will increase expression of DSX^Mand SCR in the Highline and reduce expression in the Lowline. The fluorescent pictures of antibody staining experiments indicate that the expression region of DSX^M in the Highline is significantly higher than the expression region in the Lowline, and the expression levels of SCR has minor difference among the three lines. DSX^M expression is altered by the artificial selection, but SCR expression is not. The influence of artificial selection appears to have been constrained by development. Our investigation provides an approach to test the validity of the models of cross-regulation s between SCR and DSX^M during development.</p> / Master of Science (MSc)

During the years 2006-2010 Gotland University conducted seminars excavations in Västergarn parish on Gotland. Inside the wall a total of six house foundations have been found and a total of 127 combs have been registered. This thesis is based on a material study of the 127 registered medieval combs. The purpose of this thesis is to analyze the combs and with their chronology illuminate in which period the society of Västergarn was active. And also to find out what the material remains can tell us about the place and its people. The questions concern the dating and chronology of the combs, and also how analyzing the combs can provide additional information to Västergarn. The method used is a comparative material - and literature study. The result of the analyze is that the combs are from the transitional period of the Viking - Medieval age, 900- 1100th century. A variety of nine different types could be distinguished. I believe that through an osteological –, and contextual spatial analysis and a comparative material study of the combs more information on the site can be presented.

Les techniques de génération et de traitement des signaux souffrent des limitations intrinsèques des systèmes électroniques : bande passante limitée, sensibilité aux interférences électromagnétiques, encombrement et coût. Au contraire, les systèmes optiques s’affranchissent naturellement de ces contraintes et sont potentiellement très attractifs pour la génération et le traitement des signaux. Au cours de cette thèse, nous avons étudié un système optique original utilisé pour la photonique micro-onde : les boucles à décalage de fréquence.Les propriétés temporelles de ces boucles présentent un parallèle frappant avec certaines propriétés de l’effet Talbot en optique spatiale. Cette dualité s’est révélée particulièrement riche au cours de ce travail, car elle nous a conduits à démontrer de nombreuses propriétés à la fois en optique temporelle dans les boucles à décalage de fréquence, mais aussi en optique spatiale dans des montages simples de diffraction.Nous avons ainsi mis en évidence la possibilité de calculer analogiquement la transformée de Fourier et la transformée de Fourier fractionnaire d’un signal arbitraire, avec une très bonne résolution spectrale. Ceci nous a permis de mesurer le taux de « chirp » d’un signal à modulation linéaire de fréquence, ou d’améliorer le rapport signal sur bruit de certains signaux. Nous avons également montré la possibilité de générer des trains d’impulsions avec un taux de répétition ajustable, et de faire de la mise en forme spectrale de haute résolution, en amplitude et en phase. Ce résultat permet de générer des signaux arbitraires optiques ou radiofréquences, avec des bandes passantes de plusieurs dizaines de GHz et des durées pouvant aller jusqu’à plusieurs dizaines de ns.La richesse de la dualité entre l’optique spatiale et les boucles à décalage de fréquence nous a conduits à réinterpréter un certain nombre de propriétés de l’effet Talbot (formation des images, auto-réparation des images de Talbot) et à proposer des concepts nouveaux, tels que le contrôle des images de Talbot (période et taille) ou l’amplification d’image. / Signal generation and processing techniques suffer from intrinsic limitations of electronic systems: limited bandwidth, sensitivity to electromagnetic interference, bulk and cost. On the contrary, optical systems naturally overcome these constraints and are potentially very attractive for the generation and processing of signals. During this thesis, we studied an original optical system used for microwave photonics: frequency shifting loops.The temporal properties of these loops have a strong link with some properties of the Talbot effect in spatial optics. This duality has been successful during this work, because it led us to demonstrate many properties both in time optics in the frequency shifting loops, and in spatial optics with simple diffraction setup.We have thus demonstrated the possibility of analogically calculating the Fourier transform and the fractional Fourier transform of an arbitrary signal, with a very good spectral resolution. This allowed us to measure the "chirp" rate of a linearly frequency modulated signal, or to improve the signal-to-noise ratio of some signals. We have also shown the possibility to generate pulse trains with an adjustable repetition rate, and to make spectral shaping of high resolution, in amplitude and phase. This result has been used to generate arbitrary optical or radiofrequency signals with bandwidths of several tens of GHz and durations of up to several tens of ns.The properties of the duality between spatial optics and frequency shifting loops led us to reinterpret a number of properties of the Talbot effect (image formation, self-healing of Talbot images) and to propose new concepts, such as control of Talbot images (period and size) or image amplification.

xiv, 138 p. : ill. (some col.) / In this dissertation, we demonstrate the generation of optical Raman frequency combs by a single laser pump pulse traveling in hydrogen-filled hollow-core optical fibers. This comb generation process is a cascaded stimulated Raman scattering effect, where higher-order sidebands are produced by lower orders scattered from hydrogen molecules. We observe more than 4 vibrational and 20 rotational Raman sidebands in the comb. They span more than three octaves in optical wavelength, largely thanks to the broadband transmission property of the fiber. We found that there are phase correlations between the generated Raman comb sidebands (spectral lines), although their phases are fluctuating from one pump pulse to another due to the inherit spontaneous initiation of Raman scattering. In the experiment, we generated two Raman combs independently from two fibers and simultaneously observed the single-shot interferences between Stokes and anti-Stokes components from the two fibers. The experimental results clearly showed the strong phase anti-correlation between first-order side bands. We also developed a quantum theory to describe this Raman comb generation process, and it predicts and explains the phase correlations we observe. The phase correlation that we found in optical Raman combs may allow us to synthesize single-cycle optical pulse trains, creating attosecond pulses. However, the vacuum fluctuation in stimulated Raman scattering will result in the fluctuation of carrier envelope phase of the pulse trains. We propose that we can stabilize the comb by simultaneously injecting an auxiliary optical beam, mutually coherent with the main Raman pump laser pulse, which is resonant with the third anti-Stokes field. / Committee in Charge: Dr. Steven van Enk, Chair; Dr. Michael G. Raymer; Dr. Daniel A. Steck; Dr. David M. Strom; Dr. Andrew H. Marcus

Les lasers femtosecondes à modes bloqués révèlent une structure spectrale de peigne de fréquence, couvrant plusieurs dizaines de THz. Mon travail de thèse s'est concentré sur l'étude et la mise en place d'un dispositif optique couplant le peigne laser dans une cavité optique. Le peigne et les résonances de cavités y sont délibérément désaccordés à la manière d'un Vernier, faisant apparaitre dans la transmission spectrale de la cavité un Moiré de fréquence dont la périodicité est inversement proportionnelle à ce désaccord. La première partie présente un formalisme permettant une compréhension fine de ce couplage et identifiant deux régimes en filtrages dits de «haute» résolution, où la structure de peigne est entièrement résolue, et de «basse» résolution où la résolution est donnée par le désaccord. La seconde partie décrit la réalisation expérimentale de ce couplage, détaillant la stratégie d'asservissement employée afin de stabiliser les résonances de la cavité (F=3000) par rapport au peigne laser au kHz. Enfin, ce couplage est appliqué à la spectroscopie moléculaire. Les spectres mesurés de l'air ambiant, dans des temps d'acquisition d'une seconde, exploitent l'intégralité du spectre du laser, soit 40THz (750 850nm), avec une résolution de 2GHz. La sensibilité en absorption atteint 10−9 /cm après moyenne. Cette haute sensibilité résulte d'une immunité aux bruits de conversion fréquence-Amplitude du couplage Vernier «basse» résolution et permet l'obtention d'un rapport signal sur bruit supérieur à 104. Ces performances conduisent à établir une figure de mérite de 4 × 10−11 cm−1/ √ Hz, plaçant ce résultat au troisième rang de l'état de l'art international / Femtosecond mode-Locked lasers are generators of optical frequency ‘combs’, whose distinct frequencies cover many tens or hundreds of THz. My PhD work has focused on the study and construction of a particular coupling scheme in an optical cavity, named Vernier coupling. Here, the laser comb and the cavity resonances are deliberately mismatched, as a Vernier rule. This creates Moiré pattern in the cavity spectral transmission, with a periodicity related to the inverse of the mismatch. The first part details the theory behind the coupling of laser and optical cavity modes. Two regimes are identified, called “high” resolution Vernier filtering, when the laser comb structure is probed mode by mode, and “low” resolution filtering where the linewidth of one Vernier order is given by the mismatch. The second part describes the experimental realization of this coupling scheme. It details the locking strategy used to control the resonance position of the cavity (F=3000) in regards of the laser comb (kHz scale). Finally, I present spectra recorded with this setup, focusing on molecular spectroscopy. The spectra of ambient air are recorded in acquisition times around 1 s, that cover the full bandwidth of the femtosecond laser ( 40 THz, 750-850 nm), at 2 GHz resolution. The sensitivity of the absorption measurement reaches 10−9 /cm, with averaging. This high sensitivity comes from an immunity to the frequency-To-Amplitude noise conversion of the “low” resolution Vernier coupling, leading to a signal to noise ratio better than 104. These performances give the spectrometer figure of merit of 4×10−11 cm−1/√ Hz, currently taking third place in rank international state of the art ranking