Guillaume Lavigne

Metasurface Spatial Processor for Electromagnetic Remote Control

We introduce the concept of metasurface spatial processor, whose response is remotely and coherently controlled by the superposition of an incident wave and a control wave through the metasurface. The conceptual operation of this device is analogous to that of both a transistor and a Mach-Zehnder interferometer, while offering much more diversity in terms of electromagnetic transformations. We demonstrate here two metasurfaces that perform the operations of remotely controlled electromagnetic switching and amplification. However, the proposed concept may be readily extended to many other devices, such as remotely controlled transformers providing generalized refraction, birefringence, orbital angular momentum, pulse dispersion engineering, nonreciprocity, and multiple wave processing.

Comparison of two synthesis methods for birefringent metasurfaces

Birefringent metasurfaces are two-dimensional structures capable of independently controlling the amplitude, phase, and polarization of orthogonally polarized incident waves. In this work, we propose an in-depth discussion on the mathematical synthesis of such metasurfaces. We compare the two methods, one that is rigorous and based on the exact electromagnetic fields involved in the transformation and one that is based on approximate reflection and transmission coefficients. We next validate the synthesis technique in metasurfaces performing the operations of a half- and quarter-wave plates, polarization beam splitting, and orbital angular momentum multiplexing and present the corresponding microwave experimental demonstrations.

Susceptibility Derivation and Experimental Demonstration of Refracting Metasurfaces Without Spurious Diffraction

Refraction represents one of the most fundamental operations that may be performed by a metasurface. However, simple phase-gradient metasurface designs suffer from restricted angular deflection due to spurious diffraction orders. It has been recently shown, using a circuit-based approach, that refraction without spurious diffraction, or diffraction-free, can fortunately be achieved by a transverse (or in-plane polarizable) metasurface exhibiting either loss–gain, nonreciprocity, or bianisotropy. Here, we re-derive these conditions using a medium-based—and hence, more insightful—approach based on generalized sheet transition conditions and surface susceptibility tensors, and experimentally demonstrate for the first time, beyond any doubt, two diffraction-free refractive metasurfaces that are essentially lossless, passive, bianisotropic, and reciprocal.

Perfectly refractive metasurface using bianisotropy

A passive and reciprocal perfectly refractive meta-surface is designed using a general susceptiblity synthesis method. The metasurface uses weak spatial dispersion in the form of bianisotropy to achieve perfect refraction. Its operation is validated using a full-wave simulation of the metasurface implemented with cascaded metallic layers separated by dielectric.

“Phasenna” based on a metasurface system

We introduce a metasurface-based “phasenna” (dispersive antenna with specified frequency-dependent group delay) capable of producing arbitrary group delay responses for wireless Real-time Analog Signal Processing (R-ASP) applications. This phasenna consists of a planar cavity formed by a mirror and several bandpass metasurfaces with different center frequencies, whose sequence determines the group delay response of the system. Moreover, the concept is extended to double-channel operation, simultaneously producing different group delay responses, by leveraging metasurface birefringence. Full-wave simulation results demonstrate the proposed concept. Further details and experimental results will be presented at the conference.

A guided tour in metasurface land: Discontinuity conditions, design and applications

The paper presents an overview of the recent research on metasurfaces performed in the authors group. This covers the introduction of bianistropic Sheet Transition Conditions (STCs), the subsequent elaboration of a general synthesis technique based on surface susceptibility tensors, the complementary elaboration of Finite Difference (FD) and Finite Element (FE) computational schemes for analysis, and, based upon this solid foundation, the development of a host of novel applications across the whole microwave to optical range of the electromagnetic spectrum.