Laterally heterogeneous optical films as design tools for reflectors and absorbers
Laterally heterogeneous thin solid films represent new design tools that may find applications in reflectors and absorbers from the near infrared up to the ultraviolet spectral regions. Particular examples are reflectors and absorbers based on resonant grating waveguide structures and metal island films. Because one-dimensional dielectric grating waveguide structures are optically anisotropic, these systems combine lateral periodicity with optical anisotropy and may therefore show high reflectivity and polarizing properties at normal light incidence. In combination with metals, the excitation of surface plasmon polariton modes embodies an effective absorption mechanism which may be utilized for the design of selective absorber coatings. Generally, in these systems, high absorption or reflection may be achieved even in single layer designs by a proper combination of geometrical parameters and optical materials. The purpose of this contribution is to present the results of analytical and numerical calculations as well as first experimental results for simple grating waveguide structures. Here we deal with all-dielectric systems as well as metal-based absorber designs. Analytical estimations are provided that relate the film thickness to the reflection or absorption wavelength in GWS-structures. Concerning the numerical treatment of the systems, we emphasize the use of Rigorous Coupled Wave Approximation (RCWA) calculations in thin film optics.