Dielectric metasurface based high-efficiency polarization splitters

Abstract

In this paper, a novel polarization splitter has been designed at the telecommunication wavelength of 1500 nm successfully based on the dielectric metasurface consisting of a silicon nanobrick array, which can generate two different wavefronts for two orthogonal input polarizations with well over 90% transmitted efficiency by exactly selecting the sizes of the used nanobricks. The splitting mechanism is attributed to the fact that the used nanobricks can supply two different incremental transmission phases for the X-linear-polarization (XLP) incidence and Y-linear-polarization (YLP) incidence respectively. A polarization-dependent beam splitter which can effectively deflect the X- and Y-linear-polarization incidences in the opposite direction with 90% transmitted efficiency have been realized based on the same metasurface, where the refracted angle of the co-polarized refracted light can be arbitrarily controlled by changing the lattice constant of the nanobricks. In addition, a polarization-independent beam deflector which can make the linear-polarization (XLP and YLP) incident lights refract in the same direction has also been designed and presented. However, it is very difficult to obtain concrete XLP and YLP compositions in the transmitted fields in real experiments. Thus we have designed a novel metalens to focus the two orthogonal polarization compositions in different positions. The capacities to completely manipulate the phase and wavefronts demonstrate the potential of the designed metasurfaces in realizing most free-space transmissive optical devices such as phase plates, polarizers, as well as vector beam generators and so on.