Despite the many advances and achievements in the fields of atom optics and atom cooling, there remains a wealth of dynamical detail to be filled in. While the main features of the important phenomena of atomic cooling, trapping and manipulation by electromagnetic fields are well understood, there are interesting subsidiary effects that are worth our attention. An example, which we discuss in Ch. 5 is the discovery that atomic diffusion in optical lattices may not follow the normal diffusion equation. The work reported in this dissertation represents an investigation into possible few-body effects in some atom optical configurations of interest. The effects of indistinguishability, through the exchange force, on atomic diffraction by standing wave light fields is considered in Ch. 2. In Ch. 3, after a brief overview of atomic collisions in light fields, we look at the role that the dipole-dipole interaction might play, again in atomic diffraction. Chapters 4 and 5 are concerned with optical lattices, and lay the ground work for a study of the effect of the dipole-dipole interaction on the dynamics of atoms confined in such lattices.
Despite the many advances and achievements in the fields of atom optics and atom cooling, there remains a wealth of dynamical detail to be filled in. While the main features of the important phenomena of atomic cooling, trapping and manipulation by electromagnetic fields are well understood, there are interesting subsidiary effects that are worth our attention. An example, which we discuss in Ch. 5 is the discovery that atomic diffusion in optical lattices may not follow the normal diffusion equation. The work reported in this dissertation represents an investigation into possible few-body effects in some atom optical configurations of interest. The effects of indistinguishability, through the exchange force, on atomic diffraction by standing wave light fields is considered in Ch. 2. In Ch. 3, after a brief overview of atomic collisions in light fields, we look at the role that the dipole-dipole interaction might play, again in atomic diffraction. Chapters 4 and 5 are concerned with optical lattices, and lay the ground work for a study of the effect of the dipole-dipole interaction on the dynamics of atoms confined in such lattices.
This dissertation covers the field of atom optics and is divided into four main chapters: In Chapter 2 we investigate the effects of light forces on the center-of-mass motion of two-level atoms. This will lead to the discussion of two regimes: the "ray optic" and the "wave optic" regime. In the first case, an atom is well localized in the field which allows a comparison to be made with classical ray optics. In the second case, the atom is strongly delocalized which leads to a wave treatment and allows a comparison with diffractive optics. We finish this chapter with an example in each regime: Doppler cooling for ray optics and an atomic Fabry-Perot for wave optics. In Chapter 3 we extend the results of the previous chapter to the diffraction of atoms by a standing light field. We cover three regimes in the near resonant Kapitza-Dirac effect: the Raman-Nath, the Bragg and the optical Stern-Gerlach regime. In the Raman-Nath and Bragg regimes, the wave-packet is strongly delocalized compared to the period of the standing wave. In contrast, the Stern-Gerlach regime has a small spatial extent. The Raman-Nath and Bragg regimes are differentiated in their treatment of the kinetic energy. Initially we only discuss coherent interactions. In the later half of this chapter we introduce spontaneous emission and show how its presence affects the diffraction pattern in each of these regimes. In Chapter 4 we cover various atomic cooling schemes: strong field Sisyphus cooling, adiabatic cooling, evaporative cooling, polarization gradient cooling and velocity selective coherent population trapping. We begin with a brief discussion of atomic temperature. We then cover two cooling schemes for two-level atoms. We eventually move to multi-level atoms and end this chapter with a two-atom multi-level system. In Chapter 5 we conclude with a brief discussion of practical uses and devices that may arise from atom optics such as lenses, mirrors, gravitational interferometry, lithography and atomic clocks.
In the preceding chapters, we discussed the manipulation and observation of atomic variables associated with the internal degrees of freedom. A complete separation between internal and external degrees of freedom, like position and momentum, is not always possible, however. It therefore appears appropriate to include a discussion of the mechanical effects of light, which have received increasing attention in recent years. The transfer of momentum between photons and atoms, first observed more than sixty years ago, had to wait for the wide availability of lasers to become a useful experimental tool. In particular the cooling of atoms and atomic ions to very low temperatures has found numerous applications. Light-induced forces That light exerts mechanical forces on massive particles like atoms may appear surprising. To motivate the existence of such an effect two different approaches are possible. The first approach considers the light as a collection of photons that carry, apart from energy and angular momentum, linear momentum as well. Photons interacting with atoms can therefore change the momentum of the atoms. The second approach considers light as a wave, i.e., an inhomogeneous electromagnetic field interacting with the atomic dipole moment. Both approaches provide a possible description for the numerous phenomena that can occur in this context, but in many situations, one of them turns out to be more intuitive or more useful for calculations than the other.
This book provides a thorough introduction to the interaction of atoms and atomic ions with optical and magnetic fields. Particular emphasis is placed on the wealth of important multilevel effects, where atomic vapours exhibit anisotropic behaviour. As well as covering the classic two-level atom approach to light-atom interactions, a general multi-level formalism is also described in detail, and used to discuss optical pumping, two-dimensional spectroscopy and nonlinear optical dynamics. The final chapter deals with the mechanical effects of light, including the cooling and trapping of atoms. With full theoretical and experimental coverage, and over 250 illustrations, the book will be of great interest to graduate students of laser spectroscopy, quantum electronics and quantum optics, and to researchers in these fields.
The control and manipulation of the atomic translational and internal degrees of freedom via atom-laser interaction is an essential tool in modern quantum optical experiments which allows for a large variety of applications. The present work is concerned with theoretical investigations which may shed some light on certain experiments in this field.In the first part of this work, cooperative effects in the fluorescence of dipole-dipole interacting atoms in a trap are studied. The famous macroscopic quantum jumps can occur for a single atom with a metastable state when illuminated by light. Then periods of fluorescence of fixed intensity alternate stochastically with dark periods. If one has two or three such atoms in a trap, there are dark periods and periods of single and multiple intensity, from overlap. The statistics of these periods is influenced by the dipole-dipole interaction between the atoms in a sensitive manner. This work is concerned with a theoretical description of these effects, including a discussion of the seemingly contradictory experimental results which have been obtained in this context. The main result indicates that the huge rate of double and triple jumps reported for three trapped Ba+ ions can in fact not be attributed to the dipole-dipole interaction.In the second part, the possible use of an evanescent wave atomic mirror as a measuring device for the properties of an atomic wave packet is investigated. The idea is taken from an experiment, in which such a mirror was used for the temporal diffraction of a cloud of laser cooled atoms dropping out of a magneto-optical trap. A model for the investigation of the atomic wave function with such a mirror is given, and the outcomes of different set-ups are investigated. The main result shows that with such a mirror one can sample the mod-squared of a spread-out wave function, and this opens the way for a realistic possibility for measuring this otherwise not easily accessible quantity.
In contrast to electromagnetic fields, matter-wave fields are intrinsically interacting due to the presence of atom-atom collisions. Hence, matter-wave optics becomes effectively nonlinear as soon as the atomic densities are high enough that collisions can no longer be ignored. The goal of this dissertation is to study selected aspects of atom optics under such conditions. Specifically, Chapter 2 studies the near-resonant dipole-dipole interaction between two atoms in tailored vacua. In contrast to spontaneous emission, whose rate is known to be influenced by the type of vacuum the atom interacts with, we find that the dipole-dipole potential is determined only by the free space vacuum and is not modified either by thermal or squeezed vacua. In addition in the far off-resonance regime we find that the squeezed vacuum results in an additional contribution to the effective potential governing the evolution of the atomic ground state. In the second part of the dissertation, which comprises Chapter 3, we then study several aspects of the many-body theory of atomic ultracold systems in situations where the nonlinearity arises due to the two-body dipole-dipole interaction. After a formal theoretical development we discuss the possibility of using atomic phase conjugation off Bose condensates as a diagnostic tool to access the spatial coherence properties and to measure the lifetime of the condensate. We argue that phase conjugation provides an attractive alternative to the optical methods of probing condensate proposed in the past. We further study the elementary excitations in a multicomponent Bose condensates and determine the quasi-particle frequency spectrum. We show that in that case interferences resulting from cross-coupling between the condensate components can lead to a reversal of the sign of the effective two-body interaction and to the onset of spatial instabilities.
Coherent control of matter waves using mechanical action of an electromagnetic field displays quantum duality at work. Deflecting, focussing and trapping the matter wave or de Broglie wave using optical fields lead us to develop tools to manipulate the matter waves. The emerging field provides a playground to study the newer effects of quantum coherence and quantum interference. The expansion of this area in the last three decades has enabled us to store atoms and cool them to temperatures as low as micro kelvin scale and beyond, leading to experimental realization of Bose–Einstein condensation (BEC) and of Fermi degeneracy in ultra-cold. With a focus on graduate students and young researchers, this book discusses the topics that lay the foundation stones of interaction of ultra-cold atoms with optical potentials. Key features • Developed keeping in view latest experimental advancements. • Puts light on newer theoretical advancement. • Explains the text though definitions, and useful diagrams. • Provides necessary examples and problems for the students. • Simple in language, slender, and not voluminous.