Light-wave manipulation of subwavelength metallic gratings by electrically controlling the surface charge distribution based on surface-plasmon excitation

This paper proposes a light-wave polarization response model based on a kind of subwavelength metallic grating (SMG) by controlling the rearrangement of surface free electrons and net positive charges. The action of charging interdigital SMGs to form a capacitor-shaped architecture can be used to modulate the surface charge distribution, leading to a decrease in the transmission of the incident light waves with initial polarization orientations parallel to the long axis of the grating (parallel waves or P waves) and an increase in the transmission of the incident light waves with initial polarization orientations perpendicular to the long axis of the grating (vertical waves or S waves), thus contributing to the modulation of the polarization state of the SMGs. By using serrated-shaped sidewalls for each nanostrip in the SMGs, the surface net charges can be more efficiently pumped onto the nearest apex in a linear nanotip array to clearly enhance or suppress the penetration of P waves or S waves in a wide wavelength range of approximately 200 to 2500 nm. The developed graphene-covered SMG metasurface further demonstrates a typical feature: the transmittivity of the P wave is maximally increased by 10.24% and that of the S waves is maximally decreased by 21.84% when a low dc voltage is applied because of the controlled conductive action of the graphene film formed by sequentially stacking 30 layers of single-crystal graphene over the surface of the serrated SMGs. The above behavioral attributes provide an alternative way of realizing the adjustability and controllability of the polarization response characteristics of the incident light wave and performing the fast and fine acquisition of polarization information in polarization imaging.