Light-Alignment Controllable Beam Splitter and Vectorial Displacement Sensor in the Stopped-Light Regime of Plasmonic Metasurfaces

We report the experimental realization of periodically perforated plasmonic metasurfaces capable of integrating several key functionalities, such as light-to-surface plasmon coupling, controllable beam-splitting, wavelength filtering and routing, high resolution differential wavelength measurement, and vectorial displacement sensing. The plasmonic metasurfaces operate at telecom wavelengths, at the vicinity of the eigenmode crossing points where zero group velocity is experienced, and their functionality parameters, such as sensitivity to misalignment, prong angular separation, power ratio, polarization, and bandwidth, can be adjusted by designing the boundary shape and by conveniently manipulating their alignment with the illuminating light beam. In the same context, a circular plasmonic metasurface could also serve as a vectorial displacement sensor capable of monitoring simultaneously the magnitude and direction of the displacement between its center and that of the illuminating beam. The compact, easily controllable, and all-in-one nature of our devices can enable on-chip integrated circuits with adaptable functionality for applications in sensing and optical signal processing.