Search results for "Ultra"
showing 10 items of 4451 documents
Generation of a 160-GHz transform-limited pedestal-free pulse train through multiwave mixing compression of a dual-frequency beat signal.
2002
International audience; We report the experimental generation of a 160-GHz picosecond pulse train at 1550 nm, using multiple four-wave mixing temporal compression of an initial dual-frequency beat signal in the anomalous-dispersion regime of a nonzero dispersion-shifted fiber. Complete intensity and phase characterizations of the pulse train were carried out by means of a frequency-resolved optical gating technique, showing that 1.27-ps transform-limited pedestal-free Gaussian pulses were generated.
Parabolic pulse generation in dispersion decreasing fiber amplifier
2007
We obtain an exact dispersion profile that permits for the analytical description of self-similar pulse amplification and supercontinuum generation in tapered nonlinear fiber amplifiers.
Temporal analogue of the Fresnel diffraction by a phase plate in linear and nonlinear optical fibers
2021
The analogy existing between spatial and temporal optics has motivated many studies to interpret spatial phenomena in the domain of ultrafast optics [1] . Indeed, dispersion and one-dimensional diffraction may share the same mathematical formalism. Temporal analogues of common optical systems have been proposed such as lenses, imaging systems, diffraction gratings, which opens up a whole range of new possibilities for ultrafast photonics.
Transition dynamics in optical fiber amplifiers operating in the normal dispersion regime
2011
Over the past decade there has been large interest in ultrafast optical fiber amplifiers operating in the normal dispersion regime because of the discovery that, high-energy pulses with a parabolic intensity profile and linear frequency chirp are the asymptotic solution to the system for arbitrary initial conditions [1]. These so-called “similariton” solutions propagate in a self-similar manner, holding certain relations (scaling) between pulse power, duration, and chirp parameter. While the asymptotic similariton features seem now well understood [1], the physics of the transition to this solution from arbitrary initial pulses has not been fully explored yet (most of the previous attempts …
Supercontinuum spectral-domain ghost imaging
2018
International audience; Ghost imaging is a technique that generates high-resolution images by correlating the intensity of two light beams, neither of which independently contains useful information about the shape of the object. Ghost imaging has been demonstrated in both the spatial and temporal domains, using incoherent classical light sources or entangled photon pairs. Here we exploit the recent progress in ultrafast real-time measurement techniques to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations. We demonstrate the application of this technique to broa…
On the possibility of observing bound soliton pairs in a "wave-breaking-free" mode-locked fiber laser
2007
To generate ultrashort pulses with higher energy in passively mode-locked fiber lasers, several groups have recently focused on the development of laser cavities operating in normal path-averaged dispersion, with a view to achieve wave-breaking-free operation. The mode-locking mechanism in fiber laser play a key role in providing scalability limitation: for instance, nonlinear polarization evolution can be overdriven. Furthermore, the differential gain of the doped fiber decreases along with the traveled distance. From all of these limitations, it follows that power scalability is always bounded for virtually any mode-locked laser cavity design. In general, the consequence is the emergence …
Spectral phase reconstruction of femtosecond laser pulse from interferometric autocorrelation and evolutionary algorithm
2021
International audience; We report on the complete temporal characterization of femtosecond laser pulses from second-order interferometric autocorrelation and laser spectrum measurements. The method exploits a newly developed autocorrelator based on a two photon-absorption signal produced directly within a camera sensor so as to provide a single-shot interferometric autocorrelation of great reliability and robustness. Interferometric autocorrelation trace and laser spectrum are exploited for a spectral phase retrieval via an evolutionary algorithm. The quality of the reconstruction for highly modulated spectral phases imprinted by a pulse shaper confirms the reliability of the method. The au…
Alignement moléculaire par impulsions laser ultrabrèves : Mesures & Applications
2009
The interaction of an intense ultrashort laser pulse with a molecular sample leads, after the end of the pulse, to molecular alignment at specific time under field-free conditions. This thesis is dedicated to the measurements and applications of this effect. The degree of alignment is determined through the variation of the refractive index induced by the rearrangement of the molecular dipoles. A two-dimensional technique allowing to measure molecular alignment on a single-shot basis is reported in this document. The alignment is then exploited in order to determine physical quantities which are usually difficult to estimate through others methods. The "cross-defocusing technique" has been …
Femtosecond Raman time-resolved molecular spectroscopy
2004
International audience; The applicability of several femtosecond time resolved non-linear coherent techniques such as Raman induced polarization spectroscopy (RIPS), degenerate four-wave mixing (DFWM) and coherent anti-Stokes Raman spectroscopy (CARS) for molecular spectroscopy is presented. All methods rely on the initial coherent excitation of molecular states producing wavepackets, whose time evolution is then measured. In the case of RIPS and DFWM only pure rotational transitions are involved, whereas in CARS vibrational states can be excited. First the methodology of concentration and temperature measurements using RIPS in gas mixtures involving N2, CO2, O2, and N2O is shown. In additi…
Self-Optimising Breather Ultrafast Fibre Laser
2021
We demonstrate the self-optimisation of the breather regime in an ultrafast fibre laser through an evolutionary algorithm. Depending on the specified merit function, single breathers with controllable breathing ratio and period, and breather molecular complexes with a controllable number of constituents can be obtained.