Design, fabrication, and spectral characterization of TM-polarized metamaterials-based narrowband infrared filter

Hyperbolic Metamaterials, as a non-magnetic anisotropic artificial structure, show metal properties in one direction and dielectric behavior in orthogonal directions. The proposed hyperbolic metamaterial filter in this project is designed with the metal wire mesh perpendicular to the alternative layers of dielectric materials, keeps TM center wavelength unchanged for the different angle of incident light in MDIR regime. The geometric size of this nanostructure is smaller than the working wavelength and supports big wavevectors due to hyperbolic dispersion. In contrast with conventional Bragg stack, the copper fakir bed makes the transmission properties of the filter the same. For this purpose, the state-of-the-art fabrication methods are required to make such small dimensions in alternative layers of amorphous silicon and silicon dioxide. In this work, first we demonstrate the simulation of Bragg stack with RCWA and finite element methods. Then we focus on our first-time multistep lithography method used to fabricate the filter. Finally, we experimentally verify the optical characteristic of the fabricated filter using Fourier-transform infrared spectroscopy. The experimental and spectrometry data shows that transmission properties of the hyperbolic metamaterial filter remain the same for oblique TM polarized incident light.