Method for Extracting the Equivalent Admittance from Time-Varying Metasurfaces and Its Application to Self-Tuned Spatiotemporal Wave Manipulation

TL;DR

This paper introduces an analytical method to derive equivalent admittance for time-varying metasurfaces, enabling precise spatiotemporal wave control and the design of pulse-width-dependent devices like a variable-focus Fresnel zone plate.

Contribution

It presents a novel analytical approach to model and synthesize time-varying metasurfaces with prescribed spatiotemporal responses, extending waveform selectivity to spatially inhomogeneous profiles.

Findings

Derived a method to predict metasurface responses using equivalent admittance.

Designed a pulse-width-dependent Fresnel zone plate with variable focal length.

Demonstrated potential applications in sensing, wireless communications, and signal processing.

Abstract

With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modeling a metasurface as time-varying admittance sheets, we provide an analytical calculation method to predict the metasurface time-domain responses. This allows derivation of design specifications in the form of equivalent sheet admittance, which is useful in synthesizing a metasurface with spatiotemporal control, such as to realize a metasurface with prescribed time-dependent diffraction characteristics. As an example, based on the proposed equivalent admittance sheet modeling, we synthesize a waveform-selective Fresnel zone plate with variable focal length depending on the incoming pulse width. The proposed synthesis method of pulse-width-dependent metasurfaces may be extended to designing metasurfaces with more complex spatiotemporal wave manipulation, benefiting applications such as sensing, wireless communications and signal processing.