On Peculiarities in Localization of Light in Cholesteric Liquid Crystals
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TICAL, NONLINEAR, AND SOFT MATTER PHYSICS
On Peculiarities in Localization of Light in Cholesteric Liquid Crystals A. H. Gevorgyana,*, S. S. Golika,b,**, and T. A. Gevorgyana,*** a
b Institute
Far East Federal University, Vladivostok, 690922 Russia of Automation and Control Processes, Far East Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] Received August 1, 2019; revised November 6, 2019; accepted February 14, 2020
Abstract—We have analyzed peculiarities in the localization of light in a layer of a cholesteric liquid crystal (CLC) for the normal incidence of light. It is shown that dielectric boundaries strongly affect the localization. For the minimal influence of dielectric boundaries (i.e., for ns = εm ), the total field for the eigenmodes in the CLC layer varies smoothly upon a displacement along the z axis directed along the axis of the medium (here, εm is the mean permittivity of the CLC layer and ns is the refractive index of the external medium). When ns differs from εm or when the polarization of incident light differing from the polarization of the eigenmodes, oscillations appear in the dependence of the energy of the total wave field in the CLC layer on z. It is shown that the amount of the energy stored in the CLC layer depends on ns, and the total accumulated energy in the CLC layer increases monotonically with ns. DOI: 10.1134/S1063776120060047
1. INTRODUCTION It is well known that Yablonovitch and John [1, 2] demonstrated for the first time that the structure consisting of a periodic matrix made of dielectric materials (with different refractive indices) can control the propagation of an electromagnetic wave. Later, an analogous effect was also observed in other periodic structures consisting of metal/semiconductor, metal/dielectric, etc. layers. Such media with a periodic variation of the dielectric/magnetic properties on a spatial scale on the order of the optical wavelength are known as photonic crystals (PCs) due to the similarity of their structural periodicity with the periodic potential energy in semiconducting crystals. It is well known that each PC is characterized by a certain frequency range referred to as the photonic bandgap (PBG) [3]. In this frequency interval, an electromagnetic wave cannot propagate through the crystal. This unique property of PCs renders them inimitable candidates for preparing a large number of photonic elements/devices. For preparing a PC, various chemical/optical methods and various approaches to deposition are used [4]. Laser technology was also employed for obtaining PCs after considerable advances made in the formation of the material surface structure [4]. Photonic crystals can also be self-organizing. A classical
example of self-organizing PCs are cholesteric liquid crystals (CLCs). A CLC has a birefringent structure that rotates uniformly around a certain direction known as the direction of the optical axis of the medium [5]. Cholesteric liqu
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