Supercontinuum generation in microstructured fibers and novel optical measurement techniques

Over the past few years microstructured fibers have shown potential for many practical applications and permitted significant progress in various domains such as nonlinear optics, medical science or telecommunications as the fabrication process allows for a great flexibility in the design of these fibers. In particular, small core microstructured fibers has proven to be the most efficient way for supercontinuum generation. Supercontinuum is one of the most spectacular outcome of nonlinear optics as it possesses the properties of a laser combined with an ultra-broad bandwidth spanning more than two octaves. The thesis provides a comprehensive review of the different physical mechanisms leading to the generation of these spectra in microstructured fibers. Dispersion, which reflects the dependence of the refractive index of a material on the frequency of light plays a crucial role in the pulse propagation in optical fibers or components. A novel technique to characterize the anomalous dispersion of small core microstructured fibers using short optical pulses is demonstrated. The method presents several advantages over conventional techniques and relies on the spectral modulation resulting from the evolution of the input pulse into a soliton wave. As the demand for capacity of optical networks increases, the requirements for the components employed in transmission systems becomes more stringent. In particular, the dispersion of fiber Bragg gratings or thin-film filters commonly employed in the links needs to be accurately evaluated as it may have a strong impact on the overall performance of the system. A novel method for improving the accuracy of dispersion measurements, based on the well-established phase-shift technique widely used in the characterization of optical components, is presented. The performance of diode lasers can be greatly enhanced with the use of an external cavity configuration. The wavelength tunability of the diode is increased and its linewidth considerably reduced. The behavior of the linewidth of a grating cavity laser is both theoretically and experimentally explored as the oscillation frequency of the laser is varied. Surprisingly, large changes in the linewidth value are observed, which may have an impact in applications requiring lasers with a stable and narrow linewidth. The fabrication of integrated silica-based optical components performing active functionalities is an exciting prospect for obvious reasons. Poling of silica glass is a very promising technique for the development of this type of component as it allows for the introduction of an effective second-order nonlinearity essential for performing active functions. A new technique based on the inscription of Bragg gratings for measuring the second-order nonlinearity induced by negative thermal poling is demonstrated.reviewe

Experimental Demonstration of Spectral Intensity Optical Coherence Tomography

We demonstrate experimentally quantum-inspired, spectral-domain intensity optical coherence tomography. We show that the technique allows for both axial resolution improvement and dispersion cancellation compared to conventional optical coherence tomography. The method does not involve scanning and it works with classical light sources and standard photodetectors. The measurements are in excellent agreement with the theoretical predictions. We also propose an approach that enables the elimination of potential artifacts arising from multiple interfaces

Supercontinuum light

International audienceWhen coupled into an optical waveguide, the familiar narrowband radiation from a laser can become spectrally broadened into the ultimate white light

Mid-infrared computational temporal ghost imaging

Ghost imaging in the time domain allows for reconstructing fast temporal objects using a slow photodetector. The technique involves correlating random or pre-programmed probing temporal intensity patterns with the integrated signal measured after modulation by the temporal object. However, the implementation of temporal ghost imaging necessitates ultrafast detectors or modulators for measuring or pre-programming the probing intensity patterns, which is not universally available in all spectral regions especially in the mid-infrared range. Here, we demonstrate a frequency downconversion temporal ghost imaging scheme that enables to extend the operation regime to arbitrary wavelengths regions where fast modulators and detectors are not available. The approach modulates a signal with temporal intensity patterns in the near-infrared and transfers the patterns to an idler via difference-frequency generation at the wavelength of the temporal object to be retrieved. As a proof-of-concept, we demonstrate temporal ghost imaging in the mid-infrared. The scheme is flexible and introduces new possibilities for scan-free pump-probe imaging and the study of ultrafast dynamics in spectral regions where ultrafast modulation or detection is challenging such as the mid-infrared and THz regions

Extreme events in optics: Challenges of the MANUREVA project

International audienceIn this contribution we describe and discuss a series of challenges and questions relating to understanding extreme wave phenomena in optics. Many aspects of these questions are being studied in the framework of the MANUREVA project: a multidisciplinary consortium aiming to carry out mathematical, numerical and experimental studies in this field. The central motivation of this work is the 2007 results from optical physics [D. Solli et al., Nature 450, 1054 (2007)] that showed how a fibre-optical system can generate large amplitude extreme wave events with similar statistical properties to the infamous hydrodynamic rogue waves on the surface of the ocean. We review our recent work in this area, and discuss how this observation may open the possibility for an optical system to be used to directly study both the dynamics and statistics of extreme-value processes, a potential advance comparable to the introduction of optical systems to study chaos in the 1970s

Dynamique des solitons de Kuznetsov-Ma observée en optique fibrée non-linéaire

International audienceLe soliton de Kuznetzov-Ma est une solution de l'équation de Schrödinger non-linéaire qui a été identifiée dès 1977 mais qui à ce jour n'avait encore jamais été observée expérimentalement. Nous décrivons ici une expérience mettant en évidence la dynamique du soliton KM à travers la propagation non-linéaire de breathers dans une fibre optique

Peregrine soliton in optical fiber-based systems

International audienceWe report the first observation in optics of the Peregrine soliton, a novel class of nonlinear localized structure. Two experimental configurations are explored and the impact of non-ideal initial conditions is discussed

Machine learning analysis of instabilities in noise-like pulse lasers

Neural networks have been recently shown to be highly effective in predicting time-domain properties of optical fiber instabilities based only on analyzing spectral intensity profiles. Specifically, from only spectral intensity data, a suitably trained neural network can predict temporal soliton characteristics in supercontinuum generation, as well as the presence of temporal peaks in modulation instability satisfying rogue wave criteria. Here, we extend these previous studies of machine learning prediction for single-pass fiber propagation instabilities to the more complex case of noise-like pulse dynamics in a dissipative soliton laser. Using numerical simulations of highly chaotic behaviour in a noise-like pulse laser operating around 1550 nm, we generate large ensembles of spectral and temporal data for different regimes of operation, from relatively narrowband laser spectra of 70 nm bandwidth at the -20 dB level, to broadband supercontinuum spectra spanning 200 nm at the -20 dB level and with dispersive wave and long wavelength Raman extension spanning from 1150–1700 nm. Using supervised learning techniques, a trained neural network is shown to be able to accurately correlate spectral intensity profiles with time-domain intensity peaks and to reproduce the associated temporal intensity probability distributions.publishedVersionPeer reviewe