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Lasers without Inversion and Electromagnetically Induced Transparency

Sher Alam

Published Aug 15, 1999• 21 citations
OpenAlex

Abstract

Classical Physics - Basics Non-Linear Optics - Basics Quantum Physics - Basics Coherent States and Properties of Laser Light Two-Level Systems Three-Level Systems Atomic Interference and Coherence Experiments in EIT Experiments in LWI LWI and EIT in Semiconductors 1 LWI and EIT in Semiconductors 2 and Outlook Appendix Exercises and Problems.

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Starting from the concepts of classical optics, Optics, Light and Lasers introduces in detail the phenomena of linear and nonlinear light matter interaction, the properties of modern laser sources, and the concepts of quantum optics. Several examples taken from the scope of modern research are provided to emphasize the relevance of optics in current developments within science and technology. The text has been written for newcomers to the topic and benefits from the author's ability to explain difficult sequences and effects in a straightforward and easily comprehensible way. To this second, c
Coherent phenomena based on lasing without inversion (LWI), electromagnetically induced transparency (EIT) and enhanced index of refraction are due to the interaction of light with matter. Quite recently, the coherent phenomenon of spontaneously generated coherence (SGC) has emerged as a significant one in the study of several semiconductor nanostructures. In this article, we examine the linear optical properties in the EIT regime for a three-level V-type semiconductor quantum wells (QWs) in the presence of an incoherent pump field under the SGC effect. It is shown that for a suitable choice of a SGC parameter and an incoherent pump field, the linear absorption substantially changes into a probe field gain and at the same time modifies the dispersive properties of the medium.
Summary form only given. Experiments in nonlinear optics and spectroscopy are often performed in atomic vapors, where the linewidths of the transitions of interest are dominated by Doppler broadening. In fact, several experiments on quantum coherent phenomena, such as lasing without inversion (LWI), and electromagnetically induced transparency (EIT), have been done in atomic vapors. Using the ideas of quantum coherence and interference, we propose a new scheme for obtaining subDoppler resolution at one transition of an inhomogeneously broadened, three-level atomic system, by use of an intense control field at the other transition.
The appearance of quantum interference in the microscopic world is one of the deepest mysteries at the very root of quantum mechanics. When light interacts with atoms, it can induce transitions by way of distinct but indistinguishable pathways and yield unexpected and often counter-intuitive results. Electromagnetically Induced Transparency (EIT), Coherent Population Trapping (CPT), and Lasing Without Inversion (LWI) are modern examples of phenomena where the traditional rules that govern absorption and dispersion undergo major revisions. Spectacular consequences of this new state of affairs include the ability of a light beam to propagate through a normally absorbing medium with little or no absorption, or to undergo amplification even if the active medium is not prepared in a state of population inversion. Light signals have been shown to travel with strongly subluminal group velocities of only a handful of meters per second and, even, to propagate at speed greater than the ordinary speed of light, but without violation of causality or of the established rules that control the transfer of optical information through space. Three-level atoms can interact with two coherent electromagnetic fields according to three different systems, known as Cascade, Lambda and Vee systems. The propagation of a weak probe field can be deeply affected by the presence of a second stronger beam, the so-called coupling field. Transparency windows, splitting of emission and absorption lines and enormously enhanced dispersion have been documented in numerous experiments. In this thesis we explore the physical origin of the transparency induced in these systems by the simultaneous interplay of the coupling and probe fields. We focus our attention on the Cascade system and study its two configurations, Cascade-EIT and Cascade-AT. We develop a variety of complementary approaches for the description of these two configurations, some semiclassical and others fully quantum mechanical. We prove the existence of quantum interference in Electromagnetically Induced Transparency and also the surprising absence of interference in a closely related phenomenon, known as the Autler-Townes effect. Finally we complement the traditional machinery of theoretical quantum optics with techniques borrowed from quantum scattering theory, and offer what we believe is the most convincing physical evidence for the appearance, or for the absence, of quantum interference effects.