Plasmonic polarization generator in well-routed beaming

Abstract

As one of the recent advances of optics and photonics, plasmonics has enabled unprecedented optical designs. Having a vectorial configuration of surface plasmon field, metallic nanostructures offer efficient solutions in polarization control with a very limited sample thickness. Many compact polarization devices have been realized using such metallic nanostructures. However, in most of these devices, the functions were usually simple and limited to a few polarization states. Here, we demonstrated a plasmonic polarization generator that can reconfigure an input polarization to all types of polarization states simultaneously. The plasmonic polarization generator is based on the interference of the in-plane (longitudinal) field of the surface plasmons that gives rise to versatile near-field polarization states on a metal surface, which have seldom been considered in previous studies. With a well-designed nanohole array, the in-plane field of SPPs with proper polarization states and phases can be selectively scattered out to the desired light beams. A manifestation of eight focusing beams with well-routed polarizations was experimentally demonstrated. Our design offers a new route to achieve the full control of optical polarizations and possibly advance the development in photonic information processing. Keywords: near-field interference; phase modulation; plasmonics; polarization generator INTRODUCTIONOptical polarization is an important characteristic of light that enables transmission of information for signal processing in optical information technology by utilizing classical or quantum phenomena. Compared with conventional optical elements, plasmonic devices provide a more compact and efficient means to manipulate the polarization of light (e.g., plasmonic polarizers 1-5 , polarization rotators and converters 6-11 , polarization detectors 12 , etc.). Recently, plasmoninduced spin-orbital coupling has generated strong interest in the field of photonics [13][14][15][16][17] , primarily due to the possibility of polarization and phase modulation. In fact, the vectorial structure of the surface plasmon field gives rise to unique properties in the conversion of optical fields between propagating light and bounded surface plasmon polaritons (SPPs), where the polarization information of light can be reloaded by special SPPs in a controllable way [18][19][20][21][22] . However, most of these devices offer only limited functions in polarization control. To address the ever increasing requirements of information processing, a full polarization generator is one of the desired technologies.The limitations of polarization control would obviously be overcome with the development of a polarization converter that can convert all polarization states at the same time. However, developing such an all-states polarizer in a single device is quite a challenge. Here, we demonstrate such a plasmonic polarization generator that can generate, in principle, all types of polarizations and route them selectively to the appropriate beams in...

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