Mode structure of the radiation emitted through high-gain parametric down-conversion
Notice bibliographique
Résumé
Quantumness and brightness of light are not usually found together in today’s optical quantum information, communication or measurement technologies. Yet, the last two decades saw an increased interest in the study of bright sources of nonclassical light where lossless control of their spatio-temporal spectrum promises to improve the capabilities of existing applications or to create novel ones. One of the most popular light sources for quantum optics is parametric down-conversion (PDC), a nonlinear process that occurs inside certain dielectrics where non-classical radiation originates from the parametric amplification of vacuum fluctuations. Even though the PDC process is known for almost six decades, the quantum aspects of PDC have mostly been studied at low pump power regimes. In this case, much less than one photon per mode is spontaneously produced. At strong pump power regimes, where several photons per mode are produced, PDC becomes a source of a multiphoton non-classical state of light known as bright squeezed vacuum (BSV). BSV is recognized as a good candidate for efficient light-light and light-matter interactions, multichannel quantum communications, parallel information processing, high-resolution metrology and imaging, among other applications. This thesis addresses one out of several unexplored questions regarding BSV, namely, what is its spatial modal structure? To answer this question, orthonormal modes dictated by the spatial coherence of the radiation (or so-called Schmidt modes) which also account for photon number correlations, have been considered. The Schmidt-mode formalism has been successfully used in the description of the radiation generated by low-gain PDC but their usage in the BSV case was challenging. This thesis presents several experiments that validated the results of an analytical theory for BSV based on Schmidt modes. According to the theory, the modes describing BSV, to a good approximation, are invariant to the pump power used in the process, while the photon population of each mode is not. The observed changes in the spatial intensity spectrum, spatial photon number correlations and the effects of the spatial anisotropy on the spectrum shape corroborated this prediction. Additionally, different methods for engineering the spatial spectrum of BSV were proposed and implemented by using unseeded and strongly pumped traveling-wave optical parametric amplifiers (OPAs) made of bulk nonlinear crystals, where the radiation produced is highly multimode in several degrees of freedom. For instance, spatial walk-off was exploited to obtain tunable, bright, narrowband and diffraction-limited twin beams through the amplification of the radiation in the direction of the pump Poynting vector. Alternatively, tailoring of the BSV state was achieved through the amplification of the radiation produced in one unseeded traveling-wave OPA by the presence of a second OPA, up to the generation of a single spatial mode. The modal content of the output light was further studied in terms of radial and orbital angular momentum modes. Finally, as an alternative to generation, lossless projective filtering of a single spatial BSV mode by means of a single-mode fiber was performed. The examples given in this thesis on the lossless control of the BSV spatial spectrum are extensible to the temporal domain, as proved in subsequent works. Since the elucidation of the mode structure of BSV radiation is a requirement for further development of reliable light tailoring strategies that preserve BSV nonclassical properties, this thesis is a direct contribution to the know-how that will allow full involvement of BSV in quantum technologies in the near future.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,001 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,004 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».