Near infrared and optical beam steering and frequency splitting in air holes-in-silicon inverse photonic crystals

We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime

Joint Compressed Sensing and Manipulation of Wireless Emissions with Intelligent Surfaces

Programmable, intelligent surfaces can manipulate electromagnetic waves impinging upon them, producing arbitrarily shaped reflection, refraction and diffraction, to the benefit of wireless users. Moreover, in their recent form of HyperSurfaces, they have acquired inter-networking capabilities, enabling the Internet of Material Properties with immense potential in wireless communications. However, as with any system with inputs and outputs, accurate sensing of the impinging wave attributes is imperative for programming HyperSurfaces to obtain a required response. Related solutions include field nano-sensors embedded within HyperSurfaces to perform minute measurements over the area of the HyperSurface, as well as external sensing systems. The present work proposes a sensing system that can operate without such additional hardware. The novel scheme programs the HyperSurface to perform compressed sensing of the impinging wave via simple one-antenna power measurements. The HyperSurface can jointly be programmed for both wave sensing and wave manipulation duties at the same time. Evaluation via simulations validates the concept and highlight its promising potential.Comment: Published at IEEE DCOSS 2019 / IoT4.0 workshop (https://www.dcoss.org/workshops.html). Funded by the European Union via the Horizon 2020: Future Emerging Topics - Research and Innovation Action call (FETOPEN-RIA), grant EU736876, project VISORSURF (http://www.visorsurf.eu

Single scattering and effective medium description in multilayer cylindrical metamaterials: Application to graphene and metasurface coated cylinders

Coated and multicoated cylinder systems constitute an appealing metamaterial category, as they allow a very rich and highly tunable response, resulting from the interplay of the many different geometrical and material parameters involved. Here we derive and propose an effective medium approach for the detailed description and analysis of the electromagnetic wave propagation in such systems. In particular, we investigate infinitely-long multilayered cylinders with additional electric and magnetic surface conductivities at each interface. Our effective medium approach is based on the well known in the solid state physics community Coherent Potential Approximation (CPA) method, combined with a transfer matrix-based formulation for cylindrical waves. Employing this effective medium scheme, we investigate two realistic systems, one comprising of cylindrical tubes made of uniform tunable graphene sheets and one of cylinders/tubes formed of metasurfaces exhibiting both electric and magnetic sheet conductivities. Both systems show a rich palette of engineerable electromagnetic features, including tunable hyperbolic response, double negative response and epsilon-near-zero and mu-near-zero response regions