Letteratura scientifica selezionata sul tema "Effet Autler-Townes"

We illustrate the experimental observations of Autler-Townes splitting and the spatial splitting in an electromagnetically induced transparency window in a atomic vapor system of D1 line. As the power of the dressing laser beam changes, we study first-order and secondary Autler-Townes splitting. The influences of these dressing beams, which lead to the larger spatial splitting of four-wave mixing and the shift of probe transmission signal with by changing frequency detuning. Studies on such controllable Autler-Townes splitting and spatial splitting effect can be very useful in applications of spatial signal processing and optical communication.

This paper describes an extension of the familiar coherence effects from atomic systems to the molecular regime. Such effects are inherent in the interaction of multiple laser fields with molecular systems. We have observed Autler–Townes splitting and the AC Stark shift in diatomic Lithium using the continuous wave all-optical triple resonance (AOTR) techniques. By using the Autler–Townes effect, we have partially resolved the magnetic sublevels of a molecular rovibrational level in a Doppler broadened sample, allowing all-optical alignment of the angular momentum in excited states of nonpolar molecules. The Autler–Townes effect in a molecular system extends the rovibrational state selectivity of the AOTR excitation technique to magnetic sublevels. PACS Nos.: 33.40tf, 42.50Hz

Autler–Townes (AT) splitting was theoretically investigated in the photoelectron spectra of the four-level ladder K₂ molecule driven by pump1–pump2–probe pulses using the time-dependent wave packet approach.

The effect of the triexciton state on the absorption of exciton-polaritons is studied under conditions when two high-power laser radiation pulses interacting with biexcitons and triexcitons and a probe pulse at the frequency of the exciton transition are incident on the medium. It is shown that even at low triexciton binding energies under the action of two high-power pulses, the exciton state splits into three quasi-levels, and the Autler--Townes effect (optical Stark effect) is observed. It turned out that the position of the quasi-levels depends on the detuning of the resonance of the pump pulses and their intensities, which makes it possible to identify them. These circumstances make it possible to diagnose the triexciton state in semiconductors with a higher degree of probability not by studying the absorption spectral line of the biexciton--triexciton transition, but by the effect of the triexciton state on absorption in the region of the exciton transition. Keywords: excitons, biexcitons, triexcitons, Autler--Townes effect.

We analyse the evolution of a weak probe optical field propagation through a five-level atomic medium cyclically driven by two strong optical and microwave fields. It is shown that the competition between the electromagnetically induced transparency and the Autler-Townes effect can be controlled by altering the relative phase of the coupling fields in the presence of the atomic dephasing reservoir.

Les atomes de Rydberg sont des atomes portés dans un état de grand nombre quantique principal, et dont l'électron de valence orbite très loin du noyau. Cet éloignement confère aux atomes de Rydberg des propriétés hors-normes par rapport aux atomes ordinaires, grâce auxquelles ils sont devenus le cœur de nombreux développements et applications de la physique quantique expérimentale moderne. En particulier, ils possèdent des transitions dans les domaines radiofréquence (RF) et terahertz (THz) avec de très grands éléments de matrice, qui les rendent extrêmement sensibles aux champs électromagnétiques dans ces domaines de fréquences. Cela a conduit il y a une dizaine d'années à l'émergence une nouvelle technologie de capteurs de champs RF et THz, dans lesquels l'amplitude du champ est mesurée en faisant la spectroscopie, avec un signal de transparence électromagnétiquement induite, du doublet Autler-Townes induit par l'interaction entre le champ et les états de Rydberg des atomes d'une vapeur chaude. De tels capteurs offrent plusieurs avantages intéressants par rapport aux antennes classiques, parmi lesquels une meilleure sensibilité, une plus large gamme de fréquences accessibles, une taille indépendante de la fréquence du champ mesuré, un besoin en calibration fortement réduit, et la possibilité de mesurer en plus de l'amplitude la phase et la polarisation. Tous ces avantages font des capteurs à base d'atomes de Rydberg de très bons candidats pour des applications de type télécommunications, radar, spatial, etc. Actuellement, ces capteurs font l'objet d'une multitude de travaux et d'évolutions visant à améliorer leurs performances en termes de sensibilité, d'exactitude, de bande passante de mesure, ou de résolution spatiale. L'usage d'atomes froids au lieu de vapeurs chaudes constitue pour cela une piste prometteuse, d'une part en raison de leur meilleure cohérence et de leur effet Doppler fortement réduit, et d'autre part car ils se prêtent à d'autres formes de spectroscopie potentiellement plus robustes sur certains aspects. La présente thèse porte sur l'étude expérimentale d'une nouvelle approche pour la métrologie de champs RF avec des atomes de Rydberg froids, basée sur la spectroscopie de déplétion de piège. Elle consiste à faire interagir avec le champ RF un ensemble d'atomes de ⁸⁷Rb refroidis et confinés dans un piège magnéto-optique, et à sonder le doublet Autler-Townes induit par le champ à l'aide d'un effet de déplétion du piège. Le mécanisme responsable des pertes est l'ionisation des atomes sous l'action du rayonnement de corps noir ambiant. Cette étude s'est appuyée sur la réalisation complète d'un dispositif expérimental permettant de mettre en œuvre la spectroscopie de déplétion. Malgré une faible bande passante de mesure, la méthode proposée ici a démontré une linéarité inférieure à 2%, une sensibilité de l'ordre de 250 µV/cm/Hz1/2, ainsi qu'une absence de dérives sur plusieurs heures d'intégration avec une résolution de l'ordre de 5 µV/cm. Elle offre également une plus grande simplicité de mise en œuvre que d'autres approches utilisant des atomes froids, et permet en principe de déterminer à la fois la fréquence et l'amplitude du champ. Dans ce manuscrit, nous décrirons le principe, le montage et la mise en œuvre de notre dispositif expérimental, nous présenterons les résultats des mesures effectuées grâce à lui, puis nous en analyserons les performances métrologiques, les avantages et les limites
Rydberg atoms are atoms excited to states with a very high principal quantum number, where the valence electron orbits very far from the nucleus. This large distance imparts exceptional properties to Rydberg atoms compared to ordinary atoms, which has made them central to many developments and applications of modern experimental quantum physics. In particular, they exhibit transitions in the radiofrequency (RF) and terahertz (THz) domains with very large dipole matrix elements, making them extremely sensitive to electromagnetic fields in these frequency domains. This has led over the last ten years to the emergence of a new technology of RF and THz field sensors, where the amplitude of the field is measured by performing electromagnetically induced transparency spectroscopy of the Autler-Townes doublet induced by the interaction between the field and Rydberg states of atoms in a thermal vapor. Such sensors offer several advantages over classic antennas, including a greater sensitivity, a wider frequency range, a size independent from the frequency of the measured field, a significantly reduced need for calibration, and the ability to measure, in addition to the amplitude, the phase and the polarization. All these benefits make Rydberg atoms-based RF field sensors excellent candidates for applications in telecommunications, radar systems, and the space sector. Currently, these sensors are the subject to numerous works aiming at improving their performance in terms of sensitivity, accuracy, measurement bandwidth or spatial resolution. The use of cold atoms instead of thermal vapors represents a promising avenue in these goals, due to their better coherence and strongly reduced Doppler effect. Additionally, cold atoms are suitable for other forms of spectroscopy that are potentially more robust in certain aspects. This thesis focuses on the experimental study of a new approach for RF field sensing using cold Rydberg atoms, based on trap-loss spectroscopy. It consists in making the RF field interact with a set of ⁸⁷Rb atoms cooled and confined in a magneto-optical trap, and in probing the Autler-Townes doublet created by the field through a trap depletion effect. The mechanism responsible for the losses is the ionization of the atoms under the action of background blackbody radiation. This study involved the development of an entire experimental setup to perform trap-loss spectroscopy. Despite a low measurement bandwidth, the method proposed here has demonstrated a deviation from linearity of less than 2%, a sensitivity of the order of 250 µV/cm/Hz1/2, as well as an absence of drifts over several hours of measurement, with a resolution of the order of 5 µV/cm. Moreover, this method is easier to implement than other approaches involving cold atoms, and theoretically allows for determining both the amplitude and the frequency of the field. In this manuscript, we will describe the principle, setup and implementation of our experimental apparatus, present the results of the measurement performed with it, and then analyze its metrological performance, advantages and limitations

Physics
Ph.D.
The quantum interference effects, such as the Autler-Townes (AT) effect and electromagnetically induced transparency (EIT) applied to molecular systems are the focus of this Dissertation in the context of high resolution molecular spectroscopy. We demonstrate that the AT effect can be used to manipulate the spin character of a spin-orbit coupled pair of molecular energy levels serving as a \textit{gateway} between the singlet and triplet electronic states. We demonstrate that the singlet-triplet mixing characters of the \textit{gateway} levels can be controlled by manipulating the coupling laser \textit{E} field amplitude. We observe experimentally the collisional population transfer between electronic states $G^1\Pi_g (v=12, J=21, f)$ and $1^3\Sigma _g^-(v=1, N=21, f)$ of $^7$Li$_2$. We obtain the Stern-Vollmer plot according to the vapor pressure dependence of collisional transfer rate. The triplet fluorescence from the mixed \textit{gateway} levels to the triplet $b^3\Pi_u(v'=1,J'=
Temple University--Theses

In this thesis we present a study about strong light-matter interaction in a broad single GaAs/AlGaAs quantum well representing a 3-level system. In particular we investigate the AC-Stark effect, where we observe in THz absorption spectra an Autler-Townes splitting as well as a Mollow-triplet. Compared to previous work, we showed for the first time an all-THz pump-probe experiment in the THz regime below the Reststrahlenband. Furthermore, we observe a strong frequency shift in the absorption energy of the first intersubband transition depending on the charge carrier density in the quantum well. The Autler-Townes splitting as well as the absorption frequency shift can be potentially exploited for THz-modulation applications. Beyond nonlinear optics many interesting effects occur in the strong light-matter interaction regime such as Rabi oscillations, coherent population trapping, lasing without inversion, electromagnetically induced transparency (EIT) and the AC-Stark effect. Our quantum well represents a 3-level system in which we investigate a splitting behaviour in the absorption spectrum of the first and second intersubband transition. Especially a splitting for the first intersubband transition is predicted also for electromagnetically induced transparency, while the second intersubband transition is pumped with a strong varying electric field. Naturally, a fundamental question is, how to distinguish EIT and an Autler-Townes duplet since both result in a spectrally transparent window. The method of choice for investigations combines narrowband pulses in the THz range provided by a free-electron laser and broadband THz pulses generated in a GaP crystl within a THz time-domain spectroscopy setup. In this unique configuration we perform time-resolved pump and probe spectroscopy experiments by pumping resonantly the second intersubband transition at 3.4 THz to induce a splitting of the second and third subband. Broadband THz pulses then probe an absorption splitting of about 0.2 THz related to the first intersubband transition at ≈ 2.3 THz as well as a splitting of the second intersubband transition (Mollow triplet). Analyzing experiments and using a theoretical criteria to distinguish EIT and Autler-Townes splitting, we conclude to observe an Autler-Townes doublet instead of an EIT effect.
In dieser Arbeit berichten wir über die starke Licht-Materie Wechselwirkung in 3-Niveau system anhand eines einzelnen, breiten GaAs/AlGaAs Quantentopfes. Insbesondere untersuchen wir den AC-Stark Effekt und beobachten eine Aufspaltung des Absorptionsspektrums durch das Autler-Townes Dublett und das Mollow Triplett. Im direkten Vergleich mit vorangegangenen Arbeiten zeigen wir zum ersten Mal ein reines THz Anrege-Abfrage Experiment mit Frequenzen unterhalb des Reststrahlenbandes. Weiterhin beobachten wir eine starke Frequenzverschiebung der Absorptionsenergie des ersten Intersubbandübergangs in Abhängigkeit von der Ladungsträgerdichte im Quantentopf. Sowohl das Autler-Townes Dublett als auch die Verschiebung der Absorptionsfrequenz ermöglichen potentielle Anwendung im Bereich der THz-Modulation. Im Bereich der starken Licht-Materie Wechselwirkung sind viele interessante Effekte beobachtbar wie Rabi Oszillationen, coherent population trapping, Lasern ohne Inversion, elektromagnetisch induzierte Transparenz (EIT) und der AC-Stark Effekt. Unser Quantentopf stellt ein 3-Niveau System dar, in welchem wir eine Aufspaltung der Absorption bezüglich des ersten und zweiten Intersubbandübergangs beobachten. Insbesondere für den ersten Intersubbandübergang ist auch eine Absorptionsaufspaltung durch den EIT Effekt vorhergesagt, während der zweite Intersubbandübergang durch ein starkes, elektrisches Wechselfeld angeregt wird. Es stellt sich dann die Frage, wodurch sich die Effekte EIT und Autler-Townes splitting unterscheiden, weil beide durch ein spektrales transparentes Fenster gekennzeichnet sind. Die von uns gewählte Methode verknüpft schmalbandige, starke elecktrische Wechselfelder im THz-Bereich eines freien Elektronen Lasers und breitbandigen THz-Pulsen, welche durch nichtlineare optische Effekte in einem THz Zeit-Bereichs Spektroskopie Aufbaus erzeugt werden. In dieser einzigartigen Konfiguration führen wir zeitaufgelöste Anrege-Abfrage Spektroskopie Experimente durch, in dem wir den zweiten Intersubbandübergang bei 3, 4 THz nahezu resonant anregen und das zweite und dritte Subband aufspalten. Mit breitbandigen THz Pulsen fragen wir dann die Absorptionsaufspaltung von ca. 0, 2 THz des ersten Intersubbandübergangs bei ≈ 2, 3 THz und des zweiten Intersubbandübergangs (Mollow-Triplett) ab. Nach Auswerten der Experimente und theoretischer Kriterien für die Unterscheidung zwischen EIT und Autler-Townes splitting schlussfolgern wir, ein Autler-Townes Dublett zu beobachten.

In an earlier experiment, Quesada et al.1 have observed the Autler-Townes splitting (also known as ac, optical, or dynamic Stark splitting) in the two-color four-photon ionization of H2 via the double resonant levels E,F1Σ g +(v=6,J=1) and D1Π u (ν′ =2, J′ = 2). By fitting the calculated spectra with the observed spectra, they deduced the vibronic transition moment between these two states. We present the theory for determining a number of the vibronic transition moments between the same two electronic states and thereby deducing the electronic transition moment by an inversion scheme. We calculate the Autler-Townes spectra for some representative bands of H2(D1Π u −E,F1Σ g +) and examine their dependences on laser detuning, intensity, bandwidth, and the Doppler effect. As input to our calculation, the D – E,F(v′ = 0—14, ν =1, 4, and 6) vibronic transition moments have been computed. Our investigation shows that the Autler-Townes splitting of a sufficient number of D—E,F vibronic transitions in H2 should be observable so that its electronic transition moment can be deduced.