Options
Brochard, Pierre
Nom
Brochard, Pierre
Affiliation principale
Fonction
Assistant-doctorant
Email
pierre.brochard@unine.ch
Identifiants
Résultat de la recherche
Voici les éléments 1 - 10 sur 17
- PublicationAccès libreTowards compact ultralow phase noise lasers and microwave signals based on new approachesAujourd'hui, les signaux micro-ondes à bruit de phase le plus faible sont générés optiquement par division de fréquence d'une référence optique ultra-stable utilisant un peigne de fréquence femtoseconde. Dans l'approche couramment utilisée, la référence optique ultra-stable est obtenue par stabilisation en fréquence d'un laser sur une cavité optique à très faible coefficient d’expansion thermique, et la division en fréquence est effectuée en stabilisant optiquement un laser à verrouillage de mode au laser ultra-stable. Ces deux sous-systèmes sont assez complexes et encombrants, mais ils ont démontré des performances de pointe.
Dans cette thèse, des approches alternatives ont été étudiées pour la génération de micro-ondes à faible bruit basées sur un schéma d'oscillateur de transfert. Dans une première partie, une nouvelle méthode inspirée du concept de l'oscillateur de transfert a été développée et validée pour caractériser la fréquence d’offset (décalage de phase entre la porteuse et l’enveloppe, carrier-envelope offset en anglais, CEO) d’un peigne de fréquence optique sans s'appuyer sur la méthode traditionnelle d'auto-référencement et donc sans le besoin d’un spectre optique couvrant une octave de fréquence, qui est difficile à générer notamment avec des peignes à fréquence de répétition élevée. Cette méthode a ensuite été appliquée avec succès pour caractériser trois différents types de peignes de fréquence optiques générés à partir d'un laser à semi-conducteur à verrouillage de mode, d'un laser à l'état solide pompé par diode avec un taux de répétition de 25 GHz et d'un laser à cascade quantique émettant dans la région spectrale de l’infrarouge moyen.
En modifiant et en améliorant cette technique, on a démontré et caractérisé la génération d'un signal hyperfréquence à bruit de phase ultra-faible basé sur un oscillateur de transfert. La méthode a également été mise en œuvre à l'aide d'un micro-résonateur à peigne de Kerr pour une première démonstration de principe.
En outre, la stabilisation en fréquence d'un laser continu à cascade quantique émettant dans l'infrarouge moyen sur une ligne à retard optique est présentée pour la première fois et conduit à une largeur de raie inférieure à 10 kHz en utilisant un montage en espace libre. La même approche peut être appliquée dans le proche infrarouge avec un long délai utilisant des fibres optiques, donnant la possibilité d'atteindre une largeur de raie au niveau du hertz.
Les technologies développées dans cette thèse sont des composants attrayants pour les futurs générateurs de micro-ondes compacts à très faible bruit., Today, the lowest phase noise microwave signals are generated optically by frequency division of an ultra-stable optical reference using a femtosecond frequency comb. In the commonly used approach, the ultra-stable optical reference is obtained by frequency-stabilizing a laser to a high-finesse ultra-low expansion optical cavity, and the frequency division is performed by optically locking a mode-locked laser to the ultra-stable laser. Both sub-systems are fairly complex and cumbersome, but have demonstrated state-of-the-art performance.
In this thesis, alternative approaches have been investigated for low-noise microwave generation based on a transfer oscillator scheme. In a first part, a novel method inspired by the transfer oscillator concept has been developed and validated to characterize the offset frequency of a comb spectrum without relying on the traditional self-referencing method and, thus, without requiring an octave-spanning spectrum that is challenging to be generated, especially with high repetition rate frequency combs. This method has then been successfully applied to characterize three different types of comb spectra from a semiconductor mode-locked laser, a diode-pumped solid-state laser with 25-GHz repetition rate, and a quantum cascade laser frequency comb emitting in the mid-infrared spectral region.
By modifying and improving this scheme, ultra-low phase noise microwave signal generation based on a transfer oscillator was demonstrated and characterized. The method was also implemented with a micro-resonator Kerr-comb for a first proof-of-principle demonstration of frequency division performed with a Kerr comb.
In addition, frequency stabilization of a mid-infrared quantum cascade laser to an optical delay-line is presented for the first time and led to a sub-10-kHz linewidth using only a meter-scale free-space delay-line. The same approach can be applied in the near-infrared with a long fiber delay with the potential to achieve Hz-level linewidth.
The technologies developed in this thesis are attractive components for future compact ultra-low noise microwave generators. - PublicationMétadonnées seulementRb-stabilized laser at 1572 nm for CO2 monitoringWe have developed a compact rubidium-stabilized laser system to serve as optical frequency reference in the 1.55-m wavelength region, in particular for CO2 monitoring at 1572 nm. The light of a fiber-pigtailed distributed feedback (DFB) laser emitting at 1560 nm is frequency-doubled and locked to a sub-Doppler rubidium transition at 780 nm using a 2-cm long vapor glass cell. Part of the DFB laser light is modulated with an electro-optical modula-tor enclosed in a Fabry-Perot cavity, generating an optical frequency comb with spectral cover-age extending from 1540 nm to 1580 nm. A second slave DFB laser emitting at 1572 nm and offset-locked to one line of the frequency comb shows a relative frequency stability of 1·10-11at 1 s averaging time and <4·10-12 from 1 hour up to 3 days.
- PublicationAccès libreFrequency noise correlation between the offset frequency and the mode spacing in a mid-infrared quantum cascade laser frequency comb
; ; ; Schilt, StéphaneThe generation of frequency combs in the mid-infrared (MIR) spectral range by quantum cascade lasers (QCLs) has the potential for revolutionizing dual-comb multi-heterodyne spectroscopy in the molecular fingerprint region. However, in contrast to frequency combs based on passively mode-locked ultrafast lasers, their operation relies on a completely different mechanism resulting from a four-wave mixing process occurring in the semiconductor gain medium that locks the modes together. As a result, these lasers do not emit pulses and no direct self-referencing of a QCL comb spectrum has been achieved so far. Here, we present a detailed frequency noise characterization of a MIR QCL frequency comb operating at a wavelength of 8 μm with a mode spacing of ~ 7.4 GHz. Using a beat measurement with a narrow-linewidth single-mode QCL in combination with a dedicated electrical scheme, we measured the frequency noise properties of an optical mode of the QCL comb, and indirectly of its offset frequency for the first time, without detecting it by the standard approach of nonlinear interferometry applied to ultrafast mode-locked lasers. In addition, we also separately measured the noise of the comb mode spacing extracted electrically from the QCL. We observed a strong anti-correlation between the frequency fluctuations of the offset frequency and mode spacing, leading to optical modes with a linewidth slightly below 1 MHz in the free-running QCL comb (at 1-s integration time), which is narrower than the individual contributions of the offset frequency and mode spacing that are at least 2 MHz each. - PublicationAccès libreElectrically-driven pure amplitude and frequency modulation in a quantum cascade laser
; ; ; Schilt, StéphaneWe present pure amplitude modulation (AM) and frequency modulation (FM) achieved electrically in a quantum cascade laser (QCL) equipped with an integrated resistive heater (IH). The QCL output power scales linearly with the current applied to the active region (AR), but decreases with the IH current, while the emission frequency decreases with both currents. Hence, a simultaneous modulation applied to the current of the AR and IH sections with a proper relative amplitude and phase can suppress the AM, resulting in a pure FM, or vice-versa. The adequate modulation parameters depend on the applied modulation frequency. Therefore, they were first determined from the individual measurements of the AM and FM transfer functions obtained for a modulation applied to the current of the AR or IH section, respectively. By optimizing the parameters of the two modulations, we demonstrate a reduction of the spurious AM or FM by almost two orders of magnitude at characteristic frequencies of 1 and 10 kHz compared to the use of the AR current only. - PublicationAccès libreFull stabilization and characterization of an optical frequency comb from a diode-pumped solid-state laser with GHz repetition rate
; ; - PublicationAccès libreFirst investigation of the noise and modulation properties of the carrier-envelope offset in a modelocked semiconductor laser
; ; ; ; - PublicationAccès libreCarrier-envelope offset frequency stabilization of a thin-disk laser oscillator operating in the strongly self-phase modulation broadened regime
; ; ; ; - PublicationAccès libreCarrier-envelope offset frequency stabilization of a gigahertz semiconductor disk laser
; ; ; - PublicationAccès libreCoherently-averaged dual comb spectrometer at 7.7 µm with master and follower quantum cascade lasers(2021-6)
; ; ; ; ; - PublicationAccès librePower Spectrum Computation for an Arbitrary Phase Noise Using Middleton’s Convolution Series: Implementation Guideline and Experimental Illustration
; ; Schilt, StéphaneIn this paper, we revisit the convolution series initially introduced by Middleton several decades ago to determine the power spectrum (or spectral line shape) of a periodic signal from its phase noise power spectral density. This topic is of wide interest, as it has an important impact on many scientific areas that involve lasers and oscillators. We introduce a simple guideline that enables a fairly straightforward computation of the power spectrum corresponding to an arbitrary phase noise. We show the benefit of this approach on a computational point of view, and apply it to various types of experimental signals with different phase noise levels, showing a very good agreement with the experimental spectra. This approach also provides a qualitative and intuitive understanding of the power spectrum corresponding to different regimes of phase noise.