Laser induced periodic surface structures as polarizing optical elements

Abstract

Wire grid polarizers (WGPs) are grating-type planar metasurfaces that consist of periodically aligned infinite ridges commonly placed on a uniform transparent substrate. For the far or mid infrared electromagnetic frequencies, WGPs is the only available polarizing optical element. Herein, we demonstrate a method for the realization of polarizing plates exclusively via laser structuring. We find that laser induced, periodic surface structures (LIPSS) formed on nanometer-thick metallic films which are placed on dielectric substrates can exhibit transmissive WGP operation. Using this method, we have structured 100 nm-thin Ni layers on two different dielectric substrates and produced metal-substrate-metal patterns in the form of nanowire arrays with a periodicity that can be tuned by the exciting laser wavelength. It is found that the irradiated surfaces are operating as efficient polarizing plates exhibiting high transmittance and consistent polarization response at IR and mid-IR. Numerical calculations on the polarizing efficiency stand in very good agreement with the experiment findings. Our study indicates that exploiting the LIPSS formation on sub-micron metal films can be utilized as an additional way for the fabrication of wire grid polarizing plates and may lead to new types of laser-induced meta-optics.