Comparison of Basic Frequency Selective Surface Design Methods for Optical Windows

Abstract

Methods for designing frequency selective surface for optical windows are analyzed and experimentally verified. Four methods; ITO coatings, graphene, metallic nano-coatings and metallic meshes; are compared in terms of optical transmission and shielding effectiveness (SE) characteristics. ITO is the most common method for increasing SE performance in the visible band. However, in the infrared band, transmission of ITO is limited. Metallic nano-coating is an alternative for ITO with underperformance from the SE and optical transmission viewpoint. Graphene is an emerging method and needs further development. SE performance of the graphene prevents from being a single material for shielding applications. On the other hand, it might be involved in applications where back reflection is critical because of the electromagnetic absorption characteristic. Metallic mesh is a successful candidate for applications require high level SE and optical transmission. However, dielectric properties of substrate the mesh applied, and diffraction effects should be carefully investigated.

Design and verification of periodic metallic mesh structures for optical windows

“…For the reactive part of the circuit, Ulrich's formulation is preferred [11]. For the resistive part of the circuit, frequency dependent formulation is preferred because of accuracy concerns [14], [23]. 400µm/16000µm, 100µm/4000µm and 100µm/2000µm samples were applied on 1.5mm BK7 substrate.…”

“…Transparent and conductive metal oxide coatings are famous with ITO (Indium Tin Oxide) applications. Since ITO transmits only visible and near infrared bands, it is not proper for applications with midwave, longwave infrared bands and multi-sensor systems [14]. Although graphene is a promising material, it is not yet suitable for electro-optical applications.…”

“…Production of a large pieces of Graphene flakes and transfer them from one surface to another are issues to be solved [6]. Metallic mesh structures are the most serious candidates for applications that require high optical transmission and high shielding effectiveness [14]. The spaces of the structure provide 100% transmission in the optical spectrum while metal mesh filters electromagnetic waves.…”

“…Thermal evaporation is used as a PVD (physical vapor deposition) technique. The conductivity value measured after curing gold for a period of time was recorded as one-third of the bulk gold conductivity [14]. Measured conductivity value is evaluated in analysis.…”