Catenary Structures for Spin-Dependent Coupling of Waveguide Modes

Abstract

The geometric phase in catenary structures can not only be exploited to control the propagation direction in free space, but also be used to convert freely propagating beams to guiding waves. In this chapter, we first describe how catenary apertures could realize efficient and polarization-dependent excitation of surface plasmon polaritons (SPPs). Compared with discrete structures with the same size, catenary structures have led to much higher conversion efficiency and extinction ratio between the left and right channels. Besides plasmonic optical circuits, silicon photonics is of great importance in future engineering optics, which has enabled new types of nanophotonic applications, including optical interconnects for data communications and ultra-fast optical communications systems. Especially, the high index contrast and well-established complementary metal–oxide–semiconductor (CMOS) compatible processing make silicon-on-insulator (SOI) as an attractive platform for optical information processing. Section 3.2 presents a combination of catenary subwavelength structures with SOI waveguide, which provides much more freedom for the spin-dependent light coupling. In Sect. 3.3, it is shown that a single-curved SOI waveguide could also couple circular polarized beam to different channels when the curvature is comparable to the wavelength.