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Waveguides, Resonant Cavities, Optical Fibers and Their Quantum Counterparts
Victor Bârsan
Abstract
In this chapter, we shall expose several analogies between oscillatory phenomena in mecahanics and optics.The main subject will be the analogy between propagation of electromagnetic waves in dielectrics and of electrons in various time-independent potentials.The basis of this analogy is the fact that both wave equations for electromagnetic monoenergetic waves (i.e. with well-defined frequency), obtained directly from the Maxwell equations, and the time-independent Schrodinger equation are Helmholtz equations; when specific restrictions -like behaviour at infinity and boundary conditions -are imposed, they generate similar eigenvalues problems, with similar solutions.The benefit of such analogies is twofold.First, it could help a researcher, specialized in a specific field, to better understand a new one.For instance, they might efficiently explain the fiber-optics properties to people already familiar with quantum mechanics.Also, even if such researchers work frequently with the quantum mechanical wave function, the electromagnetic modal field may provide an interesting vizualization of quantum probability density field [1].Second, it provides the opportunity of cross-fertilization between (for instance) electromagnetism and optoelectronics, through the development of ballistic electron optics in two dimensional (2D) electron systems (2DESs); transferring concepts, models of devices and experiments from one field to another stimulate the progress in both domains.Even if in modern times the analogies are not credited as most creative approaches in physics, in the early days of developement of science the perception was quite different."Men's labour ... should be turned to the investigation and observation of the resemblances and analogies of things... for these it is which detect the unity of nature, and lay the fundation for the constitution of the sciences.",considers Francis Bacon, quoted by [1].Some two centuries later, Goethe was looking for the "ultimate fact" -the Urphänomenon -specific to every scientific discipline, from botanics to optics [2], and, in this investigation, attributed to analogies a central role.However, if analogies cannot be considered anymore as central for the scientific investigation, thay could still be pedagogically useful and also inspiring for active scientific research.Let us describe now shortly the structure of this chapter.The next two sections are devoted to a general description of the two fields to be hereafter investigated: metallic and dielectric waveguides (Section 2) and 2DESs (Section 3).The importance of these topics for the development of optical fibers, integrated optics, optoelectronics, transport Waveguides, Resonant Cavities, Optical Fibers and Their Quantum Counterparts