Ultrathin Gaussian Dielectric Metasurface for Optical Transformation-Based Cloaking: Theory and Experimental...

The concept of naturally occurring visible camouflage can be extended into the electromagnetic (EM) microwave region, offering a potential application in the strategic sector. Herein, we demonstrated a cloaking effect in the microwave domain (2-6 GHz, C band) around a scatterer lying on the ground by deploying a Gaussian-shaped carpet. The initial theoretical framework comprised the design and architecture of constituents of a cloak structure, i.e., ground, scatterer, and Gaussian carpet. The Gaussian metasurface (MS) was constructed maintaining a subwavelength optical scattering condition of λ/12 for a meta-atom and λ/2 for the sublattice for the carpet, including electrical properties of the scatterer and ground. Simulation studies were performed with dielectric, diamagnetic, refractive index, and impedance functions together with a far-field environment and field propagation features including a polar scattering cross section of the carpet. They revealed a resonant EM response of 4.15 GHz, demonstrating effective ground plane restoration with reduced angular scattering. Moreover, studies offered a practical outlook to implement experimentation. Subsequently, a carpet of dimensions 780 × 30 × 6 mm3 was fabricated using commercially available Teflon (polytetrafluoroethylene, (C2F4)n, thickness of 2 mm, microwave dielectric constant of 2.1). Three laminates were bonded by load pressing at room temperature with the top laminate having a computer numerical control (CNC) machining hole pattern to embed meta-atoms. There were 250 meta-atoms additively manufactured using a BaTiO3/epoxy composite (dielectric constant of 40-45) with a diameter of 15 mm and variable height from 4.1 to 6.6 mm. Details of scatterer and ground plane fabrication are described. Experiments were carried out in an anechoic chamber in both mono- and bistatic configurations. By and large, analysis revealed that the practical version nearly mimics the theoretically proposed cloaking action.