Optical media with quasi-zero index of refraction.(Part I. Reflection and refraction of light on the boundary of vacuum and optical medium with quasi-zero index of refraction)

Background. In the effect of total internal reflection with the determined index of refraction there is formed a wave, for which the energy stream through the border is absent and all energy goes for reflection. In a considered case the index of refraction of a layer is not the fixed value, and it is represented as the continuous random value accepting numerical values in the range of admissible values from zero to a certain limiting value. It means that the concept of a sharp boundary between two media, on which the index of refraction of the optical media is the determined value, disappears, and the laws of reflection and refraction of light become non-Fresnel. In That is what is called the fundamental difference of the considered effect from the effect of total internal reflection on a boundary between two media with the fixed index of refraction. Materials and methods. A distinctive feature of the considered boundary-value problem is that the index of refraction of the composite medium possesses indeterminacy in the range from zero up to a certain $\Delta n$, defined experimentally in reflection spectra of a composite layer by disposition of the interference minima. Results. The authors solved the boundary-value problem in which the plane electromagnetic wave is reflected and refracted on a flat boundary between two media, provided one of which is a vacuum, and another one is a semi-infinite transparent optical medium with the quasizero index of refraction in the wide range of lengths of waves from 450 to 1100 nanometers. Conclusions. On the basis of the analysis of the experimental spectra of reflection and transmission of layers made from these materials the authors came to a conclusion that these materials form a new class of composite materials with the quasi-zero index of refraction. It is shown that on the boundary “air- optical medium” with the quasizero index of refraction there occurs the effect of plane surface enveloping by light. Owing to indeterminacy of the index of refraction of the medium in the considered boundary-value problem, the boundary between two media is nonhomogeneous, and the laws of reflection and refraction of a plane wave become non-Fresnel.