Abstract Laser–matter interaction is an important field of scientific research. This article discusses the response of atomic and molecular systems to laser fields and presents a review of related studies. The methodologies employed to investigate the interaction of continuous as well as pulsed lasers with atomic systems are presented. The application of laser field along with external electric and magnetic fields influence the properties of the quantum confined heterostructures. The externally applied electric and magnetic fields and confining potentials representing environmental constraints provide additional channels to control such properties. A discussion on the linear and non-linear optical properties of quantum confined systems is presented. Another experimentally viable and crucial concept which is reviewed in the present work is molecular orientation and alignment.
Abstract Laser–matter interaction is an important field of scientific research. This article discusses the response of atomic and molecular systems to laser fields and presents a review of related studies. The methodologies employed to investigate the interaction of continuous as well as pulsed lasers with atomic systems are presented. The application of laser field along with external electric and magnetic fields influence the properties of the quantum confined heterostructures. The externally applied electric and magnetic fields and confining potentials representing environmental constraints provide additional channels to control such properties. A discussion on the linear and non-linear optical properties of quantum confined systems is presented. Another experimentally viable and crucial concept which is reviewed in the present work is molecular orientation and alignment.
The goal of the present article is to review the major developments that have led to the current understanding of molecule–field interactions and experimental methods for manipulating molecules with electromagnetic fields. Molecule–field interactions are at the core of several, seemingly distinct areas of molecular physics. This is reflected in the organisation of this article, which includes sections on field control of molecular beams, external field traps for cold molecules, control of molecular orientation and molecular alignment, manipulation of molecules by non-conservative forces, ultracold molecules and ultracold chemistry, controlled many-body phenomena, entanglement of molecules and dipole arrays, and stability of molecular systems in high-frequency super-intense laser fields. The article contains 852 references.
This Thesis describes new mechanisms for controlling elastic and inelastic collisions of ultracold atoms and molecules with static electromagnetic and laser fields. The dynamical properties of ultracold atoms are usually tuned in experiments by applying an external magnetic field to induce a Feshbach resonance. The work presented in this Thesis demonstrates the possibility of inducing and manipulating Feshbach resonances with electric fields. We discuss in detail the mechanisms of electric-field-induced resonances in ultracold mixtures of alkali metal atoms and demonstrate that electric fields may shift and split the magnetic resonances. We show that electric fields may spin up the collision complex of ultracold atoms and induce anisotropic scattering which may be exploited in experiments on many-body dynamics of ultracold gaseous mixtures. The mechanisms of electric-field-induced resonances described in this Thesis allow for two-dimensional control of inter-particle interactions, leading to total control over ultracold gases. To guide future experiments, we generate accurate interaction potentials for ultracold Li--Rb mixtures by fitting positions and widths of experimentally measured Feshbach resonances. Ultracold atomic and molecular gases can be confined by laser fields in one or two dimensions which produces an optical lattice of ultracold particles. We develop a multichannel scattering theory for collisions of atoms and molecules in two dimensions and explore the effects of the confining laser potential on inelastic and reactive collisions of ultracold atoms and molecules in a 1D optical lattice. We show that ultracold collisions can be controlled in a quasi-2D geometry by varying the orientation of a magnetic field with respect to the confinement plane normal and demonstrate that the threshold energy dependence of cross sections for inelastic collisions in an optical lattice can be tuned by varying the confining potential and the magnetic field. Our results show that applying laser confinement in one dimension may stabilize ultracold systems with large scattering lengths, which may open up interesting opportunities for studies of ultracold controlled chemistry and might lead to a new research direction of ultracold chemistry in restricted geometries.
We study collision of two atoms with formation of Feshbach resonance at combined interaction with the external magnetic field and laser radiation. In cases of one- and two-photon resonances of laser radiation with two discrete vibrational molecular levels, we show that Feshbach resonances appear at interaction of external magnetic field with dressed states formed via Autler-Townes effect. In addition, in case of one-photon resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laser-induced Feshbach resonance via both Autler-Townes effect and LICS mechanism. We study the combined process of formation of Feshbach resonances; this enables the control of Feshbach resonance by varying the magnetic field and intensity and frequency of laser radiation. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs at the energy equal to that of the systems ground state. Dependence of the cross-sections on the magnetic field and laser intensity is examined in detail. In all considered cases, the scattering length is obtained depending on the magnetic and laser fields are studied. In the absence of magnetic interaction if the hyperfine substates of the quasibound state in the closed channel and those of individual colliding atoms in the open channel are the same, Feshbach resonances may arise via weak interaction between nuclear and electronic motions, which leads to transitions between electronic states. The obtained results can be employed in new studies of collisions of cold atoms, e.g., of alkali metal atoms and for interpretation of new experiments in BECs.
Confining electromagnetic fields inside an optical cavity can enhance the light–matter coupling between quantum materials embedded inside the cavity and the confined photon fields. When the interaction between the matter and the photon fields is strong enough, even the quantum vacuum field fluctuations of the photons confined in the cavity can alter the properties of the cavity-embedded solid-state materials at equilibrium and room temperature. This approach to engineering materials with light avoids fundamental issues of laser-induced transient matter states. To clearly differentiate this field from phenomena in driven systems, we call this emerging field cavity materials engineering . In this review, we first present theoretical frameworks, in particular, ab initio methods, for describing light–matter interactions in solid-state materials embedded inside a realistic optical cavity. Next, we overview a few experimental breakthroughs in this domain, detailing how the ground state properties of materials can be altered within such confined photonic environments. Moreover, we discuss state-of-the-art theoretical proposals for tailoring material properties within cavities. Finally, we outline the key challenges and promising avenues for future research in this exciting field.
This thesis is a theoretical study of the behavior of electrons in atoms and molecules subjected to external electromagnetic fields. Three electronic systems have been central in this work, the atomic and quasimolecular Rydberg states and the carbon allotrope graphene. The exaggerated properties of the highly excited Rydberg atoms, such as long lifetime, large spatial extension and low binding energy make them excellent candidates for both theoretical and experimental considerations. The analytical solutions of the hydrogen atom in quantum mechanics provide a good description for most Rydberg atoms. This is exploited in the work presented in this thesis and the accompanying papers, where we show results of numerical computations on interacting Rydberg atoms, with and without the presence of radiating fields, as well as dynamic Rydberg wave packets influenced by a train of femtosecond laser pulses. In the final part of the thesis the optical process of high-order harmonic generation in an extended molecular structure, represented by graphene, is considered. Rydberg atoms have a large dipole moment due to the large average electronic radius in the atom, which leads to a very strong dipole-dipole coupling between interacting particles in a gas of cold Rydberg atoms. This interaction, which is dependent on the internuclear separation between the atoms, induces a shift in the energy levels, which again prohibits the excitation of more than one atom in the gas, an effect commonly known as the Rydberg blockade. A correlated behavior is observed for the intrashell transitions in mutually excited Rydberg atoms. The microwave field driven dynamics is significantly supressed for internuclear distances below a given conditional radius which scales linearly with the principal quantum number n. Such an entangled electronic behavior may open for the realization of quantum gates applied in quantum informatics. The long-range interaction of Rydberg atoms is dominated by the dipole-dipole terms. Nevertheless, the investigation of two interacting Rydberg atoms, without the influence of electromagnetic radiation, has shown that the lower order multipolar terms play a vital role in the energy shifts as well as for the electronic probability distributions. We found that the energy curves, when including all multipole orders, correspond to both repulsive and attractive states with a stronger repulsion than attraction. We also propose a laser assisted approach for stabilization of Rydberg gases by controlled transitions between such attractive and repulsive energy states. Single-electron ionization of a dynamic Rydberg wave packet confined within a single energy level has been investigated. The ionization probability of an intrashell Rydberg wave packet depends strongly on the degree of polarization. For a wave packet driven repeatedly between the circular (least polarized) state and the linear (most polarized) state by a rotating microwave field and subjected to a train of femtosecond laser pulses, the ionization probability will depend crucially on the laser repetition rate and number of pulses. The angular-resolved ionization probability and energy distribution in the continuum are also influenced by these parameters. The last part of the thesis is devoted to the study of high-order harmonic generation (HHG) in graphene. In the simple man’s model HHG can be described by an electron that is ionized and driven in an external field, after which it returns to the parent atom and recombines, emitting a high-energy photon with frequency that is a multiple of the incident laser frequency. We show that the harmonic spectra obtained from the interaction with linearly as well as circularly polarized femtosecond lasers yield harmonics up the classical limit for extended molecules. In contrast to diatomic molecules, the stable grid structure of graphene ensures that the harmonic generation cutoff remains constant with increasing signal power as the graphene diameter extends beyond the classical limit. Additionally, for circularly polarized lasers harmonics exceeding the classical predictions have been observed.
Quantum optics is the branch of physics that investigates the interaction of light with matter at the quantum level, where the discrete nature of photons and quantum states of atoms, molecules, and solid-state systems become dominant. Quantum optics systems provide the experimental and theoretical foundation for understanding nonclassical states of light, quantum coherence, entanglement, and measurement at the quantum limit. Over the past few decades, advances in laser technology, nonlinear optics, and precision measurement have transformed quantum optics from a fundamental discipline into a key enabler of quantum technologies, including quantum communication, quantum computing, quantum sensing, and quantum metrology. This review presents a comprehensive overview of the physical principles, system architectures, and experimental platforms of quantum optics. Emphasis is placed on light sources, atom–photon interaction systems, detection techniques, and emerging applications, along with current challenges and future research directions.