Polarization scrambling with metallic meander structures for space applications

Abstract

Periodic single metallic meander structures have been shown to exhibit extraordinary transmission in the visible frequency domain within a well-defined pass band that can be shifted by geometry variation. Furthermore, meander structures are not only linear polarizers but also induce phase retardation between s- and p-polarized light. In addition, they are able to convert the polarization of light due to plasmonic excitations. Those features combined with the advantages of plasmonic metamaterials in general, such as radiation stability, temperature independence and low weight make them perfect candidates for optical devices in space instruments. We show analytically and numerically that an optical depolarizer can be designed by spatially distributing meander structures in a pixel-like fashion and rotating each element by a random angle. The depolarizing properties of meander structures, indicated by the Mueller matrix elements, are investigated for various geometrical parameters and can be improved by stacking two meander structures onto each other. The presented polarization scrambler can be flexibly designed to work anywhere in the visible wavelength range with a bandwidth of up to 100 THz. Furthermore, the depolarization effect relies on optical activity rather than scattering. With our preliminary design, we achieve depolarization rates larger than 60% for arbitrarily polarized, monochromatic or narrow-band light, respectively. One advantage of our concept is the flexibility to tune the polarization scrambler to a particular optical frequency or functionality. Circularly polarized light (S = [1, 0, 0, ±1]) for instance could be depolarized by 95% at 600 THz.