The light wave flow effect in a plane-parallel layer with a quasi-zero refractive index under the action of bounded ligh
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MOLECULES, OPTICS
The Light Wave Flow Effect in a Plane-Parallel Layer with a Quasi-Zero Refractive Index under the Action of Bounded Light Beams O. N. Gadomsky* and I. A. Shchukarev** Ul’yanovsk State University, Ul’yanovsk, 432017 Russia *e-mail: [email protected] **e-mail: [email protected] Received November 20, 2015
Abstract—It is shown that external optical radiation in the 450–1200 nm range can be efficiently transformed under the action of bounded light beams to a surface wave that propagates along the external and internal boundaries of a plane-parallel layer with a quasi-zero refractive index. Reflection regimes with complex and real angles of refraction in the layer are considered. The layer with a quasi-zero refractive index in this boundary problem is located on a highly reflective metal substrate; it is shown that the uniform low reflection of light is achieved in the wavelength range under study. DOI: 10.1134/S1063776116070050
1. INTRODUCTION In [1–3], the boundary problems of the interaction of plane electromagnetic waves with a plane interface between a vacuum and a semi-infinite medium with a quasi-zero refractive index and of the interaction of plane electromagnetic waves with a plane-parallel layer that has a quasi-zero refractive index on the surfaces of semi-infinite absorbing and nonabsorbing optical media were solved. In this paper, we solved the boundary problem of the interaction of a bounded light beam with a plane-parallel layer that has a quasizero refractive index on the surface of a semi-infinite transparent or absorbing medium. It is known [4–6] that the interaction of a spatially bounded light beam with the interface of two media in the case of total internal reflection is accompanied by longitudinal and transverse displacements of the reflected beam with respect to the incident beam. The longitudinal displacement of the beam is comparable to its penetration depth into the medium and is of the order of magnitude of the external radiation wavelength. Because of diffraction caused by the finite diameter of the incident beam, along with the longitudinal displacement of the beam a lateral wave that propagates along the surface is observed, which plays the role of a waveguide. The lateral wave occurs when the angle of incidence of the beam exceeds the critical angle only by ~ 1° and propagates over a distance that exceeds the longitudinal displacement by several orders of magnitude. The lateral wave intensity is considerably smaller (approximately 108 times) than that
of the incident light beam; therefore the main energy of the incident light is transformed to the energy of reflected light with a reflection power close to unity. We show in this paper that upon the incidence of a spatially bounded light beam from a vacuum on a layer with a quasi-zero refractive index, new, compared to the known [4–6], light reflection regimes occur. These are related to the random refractive index of the layer in the region of admissible values from zero to some value Δn2 determined from experimental
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