Some aspects of quantum well physics are very closely related to atomic and molecular physics. Quantum well and quantum dot semiconductor structures are, in some sense, artificial atoms (single well structures) and molecules (multiple well structures). We use this analogy to extend the ideas and results on laser interaction with atoms and molecules to the physics of laser interaction with quantum wells. We also try to use ideas developed in quantum well physics to understand molecular phenomena. For example, motivated by the analogy between quantum wells and atoms, we have experimentally demonstrated all-optical control of the direction of photocurrent in quantum well devices.
Some aspects of quantum well physics are very closely related to atomic and molecular physics. Quantum well and quantum dot semiconductor structures are, in some sense, artificial atoms (single well structures) and molecules (multiple well structures). We use this analogy to extend the ideas and results on laser interaction with atoms and molecules to the physics of laser interaction with quantum wells. We also try to use ideas developed in quantum well physics to understand molecular phenomena. For example, motivated by the analogy between quantum wells and atoms, we have experimentally demonstrated all-optical control of the direction of photocurrent in quantum well devices.
Nanotechnologically fabricated structures out of compound semiconductor materials make up the functional parts in LEDs, in semiconductor lasers and in electronics components. The small size of the structures evidently leads to requiring the modeling to look at phenomena at the quantum level. Especially for optoelectronical devices, one needs to treat the interaction between light and semiconductor material. This research adds to the understanding of inter-pretations of light-matter interaction phenomena and makes it possible to find totally new and undiscovered functionalities in semiconductor nanostructures. \nThis thesis presents work on modeling and creates new theoretical foundations for phenom-ena appearing in semiconductor quantum structures. Of special interest has been to generate a theoretical description to such phenomena that have been caused by an optical field and in which one sees changes, e.g., in angular momentum or spatial distribution of excited states. Basically, two kinds of structures are examined, quantum rings and wells. A quantum ring is a toroidal object of which volume is very small, but its diameter can be significant when com-pared to the wavelength of light. Another class of systems under study is a double quantum well structure, where there are two quantum wells on both sides of a tunnel barrier. In this system, the type-I and type-II semiconductor band-structure properties become combined in spatial coordinates, since the electrons and holes can occupy either the same or the separate quantum wells. \nThe two most interesting results are the angle-of-emission dependent photoluminescence from the quantum rings and the coherent control of vertical transport of desired quasiparticles through material interfaces in the quantum-well system in a selective manner. Since the ob-tained results on quantum rings are closely connected to the orbital-angular-momentum coupling between light and matter, they can prove to be important in different quantum infor-mation schemes where this angular-momentum aspect of light has been found to be highly beneficial. In quantum optics, there already are visible trends towards this direction. The predicted coherent control in a double-quantum-well system may mean a large technological progress, since by utilizing this effect one can study transport properties between materials over an interface, one of the most interesting examples of such phenomena being the transfer of quantum correlations through the interface without changing the local densities of electrons.
Atomic, molecular and optical physics is a field which, during the last few decades, has known spectacular developments in various directions, like nonlinear optics, laser cooling and trapping, quantum degenerate gases, quantum information. Atom–photon interactions play an essential role in these developments. This book presents an introduction to quantum optics which, I am sure, will provide an invaluable help to the students, researchers and engineers who are beginning to work in these fields and who want to become familiar with the basic concepts underlying electromagnetic interactions. Most books dealing with these subjects follow either a semi-classical approach, where the field is treated as a classical field interacting with quantum particles, or a full quantum approach where both systems are quantized. The first approach is often oversimplified and fails to describe correctly new situations that can now be investigated with the development of sophisticated experimental techniques. The second approach is often too difficult for beginners and lacks simple physical pictures, very useful for an initial understanding of a physical phenomenon. The advantage of this book is that it gives both approaches, starting with the first, illustrated by several simple examples, and introducing progressively the second, clearly showing why it is essential for the understanding of certain phenomena. The authors also clearly demonstrate, in the case of non-linear optics and laser cooling, how advantageous it may be to combine both approaches in the analysis of an experimental situation and how one can get from each point of view useful, complementary physical insights.
The observation of man-made quantum size effects is now possible due to advances in semiconductor technology. Interest in quantum-well heterostructures and superlattices has added a new dimension to both the application and perspective of the traditional discussion of a particle in a box. This paper addresses these new perspectives and presents in an elementary manner the techniques employed to model single and multiple square wells in semiconductors. A brief overview of semiconductor microlayer devices is followed by a discussion of the physics of quantum-well heterostructures. Since the behavior of these structures is described by the finite square well, a simple iterative technique to solve for the bound states of single or multiple (coupled) square wells is presented. The iterative technique is quite general and powerful, yet the physical ideas and the mathematics are straightforward and simple. Finally, computer simulation is employed to illustrate the interaction between multiple coupled wells; the results are compared with those obtained via the usual Kronig–Penney model.
Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review the basic tools for coherent atom optics are described including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on atom chips. Scientific advances in a broad range of fields that have resulted from the application of atom interferometers are reviewed. These are grouped in three categories: (i) fundamental quantum science, (ii) precision metrology, and (iii) atomic and molecular physics. Although some experiments with Bose-Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e., phenomena where each single atom interferes with itself.
Motivation You may ask why one needs to know about quantum mechanics. Possibly the simplest answer is that we live in a quantum world! Engineers would like to make and control electronic, opto-electronic, and optical devices on an atomic scale. In biology there are molecules and cells we wish to understand and modify on an atomic scale. The same is true in chemistry, where an important goal is the synthesis of both organic and inorganic compounds with precise atomic composition and structure. Quantum mechanics gives the engineer, the biologist, and the chemist the tools with which to study and control objects on an atomic scale. As an example, consider the deoxyribonucleic acid (DNA) molecule shown in Fig. 1.1. The number of atoms in DNA can be so great that it is impossible to track the position and activity of every atom. However, suppose we wish to know the effect a particular site (or neighborhood of an atom) in a single molecule has on a chemical reaction. Making use of quantum mechanics, engineers, biologists, and chemists can work together to solve this problem. In one approach, laser-induced fluorescence of a fluorophore attached to a specific site of a large molecule can be used to study the dynamics of that individual molecule. The light emitted from the fluorophore acts as a small beacon that provides information about the state of the molecule.
This book introduces the fundamental quantum physics of atoms and molecules. Divided into three parts, the first provides a historical perspective leading to the contemporary view of atomic and molecular physics, outlining the principles of non-relativistic quantum mechanics. The second part covers the physical description of atoms and their interaction with radiation, whilst the third part deals with molecular physics. The book is the first of a series of three aiming to present a broad coverage of atomic, molecular, solid-state and statistical physics. It is well suited accompany a one-semester undergraduate course in quantum physics but will be enjoyed by anyone trying to enter the realm of atoms and molecules and how we understand them.