Light propagation in stratified media with soft interfaces
Faculty of Sciences. Physics
Physical review : B : condensed matter and materials physics. - Lancaster, Pa, 1998 - 2015
, 6 p.
University of Antwerp
The propagation of light through materials in which the density of charge carriers varies smoothly on a scale smaller than or comparable to the wavelength requires a description that goes beyond the commonly used Fresnel equations. We propose a method to solve Maxwell's equations in such a way that any linear response theory for the bulk material can be combined with a given smooth density profile for the (free or bound) charge carriers. This method is implemented for linearly polarized monochromatic light impinging on inhomogeneous multilayer systems, leading to a fast algorithm that yields reflectance and transmittance for such systems. We apply our algorithm to investigate the difference in optical response between smooth interfaces and abrupt interfaces in stratified systems where the materials can have complex bulk permittivities, and find that the smoothening of the interface on a wavelength scale significantly reduces reflection in favor of absorption. This result is of importance to current experiments that aim to detect metallic hydrogen and deuterium films using their optical response. Our results show that for a correct interpretation of these experiments it is important to consider the smoothness of the density profile of the metallic layer. Also, for nonabsorbing layers, a smooth, rather than abrupt transition, can have an important impact on the design of optical filters.