18 research outputs found
Analyse modale d'un peigne de fréquences femtoseconde : Correlations spectrales classiques et quantiques
In this thesis, we investigate the usage of an optical femtosecond frequency comb for precision measurements at the quantum limit, as well as the fluctuations of the combs structure. We use a formalism that is borrowed from quantum optics to describe classical phenomenon. We show indeed that the comb structure can be decomposed on a basis of modes, where each of these is attached to a given physical parameters. In a projective measurement scheme, we show that it is then possible to measure an information carried by the electromagnetic field (such as a delay in time) as well as fluctuations from the laser source (in that example, the timing jitter). We finally propose a scheme to generate two beams that are "squeezed in time", since they allow to measure a delay with a better sensitivity than using classical resources.Dans cette thèse, nous étudions les applications aux mesures de précision à la limite quantique d'un peigne de fréquence optique dans le régime femtoseconde, ainsi que les fluctuations de sa structure spectrale. Pour cela, nous utilisons un formalisme emprunté au domaine de l'optique quantique. Nous démontrons que la structure du peigne peut effectivement être décomposée sur une base de modes, dont chacun est relié à un paramètre physique. À l'aide de mesures projectives, nous montrons qu'il est alors possible d'accéder à une information portée par le champ électromagnétique (tel le délai temporel d'une impulsion), ainsi qu'aux fluctuations de la source laser (en analogie, la gigue temporelle). Finalement, nous proposons l'élaboration d'un système pour générer deux faisceaux quantiques "comprimés en temps", puisqu'ils permettent de mesurer un délai avec une sensibilité accrue par rapport à l'utilisation de ressources classiques
Recovering the dynamics of optical frequency combs from phase-amplitude noise correlations measurements
Controlling the noise properties of optical frequency combs (OFC) is of great
importance as most OFC-based precision measurements are limited by their
intrinsic stability. It has been found that OFC noise manifests itself as
fluctuations of only a few global parameters, which indicates strong
correlations between the fluctuations of individual frequency lines. However,
the physical processes underneath such correlations are still not completely
understood. We introduce a novel measurement scheme that allows us to measure
simultaneously and in real time the whole Fourier spectrum of phase and
amplitude fluctuations of the OFC field as well as its amplitude-phase
correlations in many frequency bands spanning the laser spectrum. This enables
us to determine the full quadrature covariance matrices in the frequency band
mode basis, and this for various Fourier frequencies, to find their principal
modes in time and frequency domain, and to associate them with global physical
parameters