Parametric excitation of multiple resonant radiations from localized wavepackets

Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special fiber optics system characterized by a dispersion oscillating along the propagation coordinate, which mimics "time". The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets sustained by the fiber nonlinearity into free-running linear dispersive waves (continuum), at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of the fact that the localized state is a soliton-like pulse or a shock front

Resonant Kushi-comb-like multi-frequency radiation of oscillating two-color soliton molecules

Nonlinear waveguides with two distinct domains of anomalous dispersion can support the formation of molecule-like two-color pulse compounds. They consist of two tightly bound subpulses with frequency loci separated by a vast frequency gap. Perturbing such a two-color pulse compound triggers periodic amplitude and width variations, reminiscent of molecular vibrations. With increasing strength of perturbation, the dynamics of the pulse compound changes from harmonic to nonlinear oscillations. The periodic amplitude variations enable coupling of the pulse compound to dispersive waves, resulting in the resonant emission of multi-frequency radiation. We demonstrate that the location of the resonances can be precisely predicted by phase-matching conditions. If the pulse compound consists of a pair of identical subpulses, inherent symmetries lead to degeneracies in the resonance spectrum. Weak perturbations lift existing degeneracies and cause a splitting of the resonance lines into multiple lines. Strong perturbations result in more complex emission spectra, characterized by well separated spectral bands caused by resonant Cherenkov radiation and additional four-wave mixing processes

Tunable Modulational Instability Sidebands via Parametric Resonance in Periodically Tapered Optical Fibers

We analyze the modulation instability induced by periodic variations of group velocity dispersion and nonlinearity in optical fibers, which may be interpreted as an analogue of the well-known parametric resonance in mechanics. We derive accurate analytical estimates of resonant detuning, maximum gain and instability margins, significantly improving on previous literature on the subject. We also design a periodically tapered photonic crystal fiber, in order to achieve narrow instability sidebands at a detuning of 35 THz, above the Raman maximum gain peak of fused silica. The wide tunability of the resonant peaks by variations of the tapering period and depth will allow to implement sources of correlated photon pairs which are far-detuned from the input pump wavelength, with important applications in quantum optics.Comment: 15 pages, 7 figure

Nonlinear and Quantum Optics with Whispering Gallery Resonators

Optical Whispering Gallery Modes (WGMs) derive their name from a famous acoustic phenomenon of guiding a wave by a curved boundary observed nearly a century ago. This phenomenon has a rather general nature, equally applicable to sound and all other waves. It enables resonators of unique properties attractive both in science and engineering. Very high quality factors of optical WGM resonators persisting in a wide wavelength range spanning from radio frequencies to ultraviolet light, their small mode volume, and tunable in- and out- coupling make them exceptionally efficient for nonlinear optical applications. Nonlinear optics facilitates interaction of photons with each other and with other physical systems, and is of prime importance in quantum optics. In this paper we review numerous applications of WGM resonators in nonlinear and quantum optics. We outline the current areas of interest, summarize progress, highlight difficulties, and discuss possible future development trends in these areas.Comment: This is a review paper with 615 references, submitted to J. Op

Optically mediated nonlinear quantum optomechanics

We consider theoretically the optomechanical interaction of several mechanical modes with a single quantized cavity field mode for linear and quadratic coupling. We focus specifically on situations where the optical dissipation is the dominant source of damping, in which case the optical field can be adiabatically eliminated, resulting in effective multimode interactions between the mechanical modes. In the case of linear coupling, the coherent contribution to the interaction can be exploited e.g. in quantum state swapping protocols, while the incoherent part leads to significant modifications of cold damping or amplification from the single-mode situation. Quadratic coupling can result in a wealth of possible effective interactions including the analogs of second-harmonic generation and four-wave mixing in nonlinear optics, with specific forms depending sensitively on the sign of the coupling. The cavity-mediated mechanical interaction of two modes is investigated in two limiting cases, the resolved sideband and the Doppler regime. As an illustrative application of the formal analysis we discuss in some detail a two-mode system where a Bose-Einstein condensate is optomechanically linearly coupled to the moving end mirror of a Fabry-P\'erot cavity.Comment: 11 pages, 8 figure

Analyse des Solitonengehaltes von optischen Impulsen in Glasfasern

Der Solitonengehalt von Lichtimpulsen in einer Glasfaser wird untersucht. Dabei wird ein neu entwickeltes Verfahren angewendet, welches auf der spektralen Analyse der Schwebunsstrukturen beruht. Dieses Verfahren ist in der Lage, den allemeinen Solitonengehalt zu bestimmen, sogar für nichtintegrable Systeme. Dies war bisher nur Näherungsweise möglich. Aus der vorgestellten Analyse wird ein Messprinzip abgeleitet, mit dem sich der Solitonengehalt bestimmen lässt. Dies wird anhand einer Beispielmessung demonstriert

Parametric resonance of ground states in the nonlinear Schrödinger equation

AbstractWe study the global existence and long-time behavior of solutions of the initial-value problem for the cubic nonlinear Schrödinger equation with an attractive localized potential and a time-dependent nonlinearity coefficient. For small initial data, we show under some nondegeneracy assumptions that the solution approaches the profile of the ground state and decays in time like t-1/4. The decay is due to resonant coupling between the ground state and the radiation field induced by the time-dependent nonlinearity coefficient

Phase Control in Atomic Coherence

In this thesis, atomic coherence is used to enhance nonlinear optical processes in multi-level atoms. The multi-photon transitions are driven resonantly, and at the same time without absorptive losses, by using electromagnetically induced transparency (EIT), thereby allowing the study of χ(3) and χ(5) nonlinearities using weak driving fields. The coherently modified probe beam(s) and the atom-radiated signal fields arising from four- and six- wave- mixing (FWM and SWM) processes are measured in the spectral, temporal and spatial domains. In a three-level ladder-type atomic system, multiple peaks having spectral asymmetries are observed in the EIT window as well as in the FWM signal waveforms due to the diverse multiplicities of the participating atomic states. Using phase control tailored in the frequency domain, we demonstrate all-optical methods to control these spectral waveforms and discuss applications involving waveform-shaping and metrology. For the EIT study we demonstrate a switching of multiple dark peaks into bright peaks via phase-control of interferences in the underlying dark-states. In the FWM study we demonstrate all-optical spectral line shape symmetrization, linewidth narrowing and bandwidth switching. In a four-level inverted-Y-type atomic system, we drive and measure coexisting and phase-matched FWM and SWM signals. By using precision control of the relative phase and amplitude between these two processes of different nonlinear orders, we demonstrate phase coherence between them. First, a single-phase measurement is performed in the temporal and spatial domains, and the interferogram is used to measure the resonant frequency of the 5D5/2-5P3/2 atomic transition in 85Rb. Second, the method is extended to realize a capacity for two-phase measurement. In this case, the spectral bandwidth of the signal is modified in order to measure the phase-shift occurring in one Mach-Zehnder interferometer, while the intensity of the total signal waveform measures the phase-shift occurring in a second interferometer. Finally, we demonstrate phase-dependent spatial fusion between two ultra-weak optical fields by using a strong coupling field to first convert the weak fields into bosonic dark-state polaritons, which are then steered into a common all-optical waveguide mode arising due to the coupling field\u27s intensity distribution and the resulting cross-Kerr refractive index gradient

Optimization of passive ultrafast fiber lasers based on indium nitride for novel applications

Los láseres ultrarrápidos en fibra constituyen una de las fuentes de luz más utilizadas actualmente debido a su fiabilidad y flexibilidad, convirtiéndose en la pieza clave de múltiples aplicaciones, como las comunicaciones ópticas, el procesamiento de materiales o la espectroscopía. Entre ellos, los láseres en fibra anclado en modos basados en el uso de absorbentes saturables demuestran características superiores de estabilidad, simplicidad y bajo coste, capaces de emitir pulsos ultracortos con potencias extremadamente altas en un amplio rango espectral. En las últimas décadas, se han probado varios absorbentes saturables, donde los materiales de semiconductor destacan por su amplia profundidad de modulación, su elevada absorción no lineal y su baja intensidad de saturación. Sin embargo, presentan algunas limitaciones como un estrecho ancho de banda y un bajo umbral de daño. Por tanto, en este trabajo se propone el uso de un semiconductor de InN en un láser todo en fibra anclado en modos para la generación de láseres ultrarrápidos de alta potencia en la región del infrarrojo cercano. Esta configuración ha demostrado trenes de pulsos Gaussianos en el rango de los femtosegundos mediante un sistema sencillo y de bajo coste. En esta tesis, el objetivo es optimizar las características de un láser de fibra anclado en modos basado en un absorbente saturable de InN, y desarrollar un novedoso dispositivo espectroscópico para aplicaciones de detección. Primeramente, se estudia la mejora de las propiedades del absorbente saturable de semiconductor mediante un mayor control del dopaje residual así como del crecimiento de material, demostrando el máximo comportamiento no lineal para este tipo de absorbentes saturables en un láser en fibra. También se discute como estas características podrían mejorarse mediante el desarrollo de un nuevo diseño de láser totalmente en fibra, capaz de contrarrestar las limitaciones actuales de ruido y perdidas de inserción dentro de la cavidad láser. De este modo, se demuestra la duración de pulso más corta y la máxima potencia óptica, conservando una configuración sencilla, lo que allana el camino hacia el desarrollo de sistemas láser comerciales en aplicaciones de alta potencia. A continuación, se introducen nuevas aplicaciones potenciales del sistema láser de fibra: en la detección de gases, mediante la generación de supercontinuo del pulso láser ultrarrápido en fibras monomodo capaces de cubrir espectros de absorción más amplios; y en la caracterización de moléculas biológicas mediante el uso de una novedosa estructura espectroscópica SF-CARS conectada a la fuente láser totalmente en fibra. Además, se exponen las implicaciones del chirp-matching en el rendimiento de la medición de la absorción, y el impacto de la dispersión y los efectos no lineales generados por diferentes fibras ópticas en la compresión y el ensanchamiento de los pulsos de fibra ultrarrápidos. La configuración láser propuesta supera la máxima resolución medible y la cobertura espectral, las limitaciones más importantes a las que se enfrenta la espectroscopía moderna. Finalmente, se resumen los objetivos alcanzados en esta tesis, evaluando el potencial de las aplicaciones propuestas, así como futuras líneas de investigación basadas en dichos hallazgos