Harmonic information transitions of spatiotemporal metasurfaces

Haotian Wu,Tie Jun Cui,Qiang Cheng,Lianlin Li,Xin Xin Gao,Guo Dong Bai,Lei Zhang

doi:10.1038/s41377-020-00441-1

Haotian Wu, Tie Jun Cui + Show 5 more

Open Access

https://doi.org/10.1038/s41377-020-00441-1

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Abstract

Facilitated by ultrafast dynamic modulations, spatiotemporal metasurfaces have been identified as a pivotal platform for manipulating electromagnetic waves and creating exotic physical phenomena, such as dispersion cancellation, Lorentz reciprocity breakage, and Doppler illusions. Motivated by emerging information-oriented technologies, we hereby probe the information transition mechanisms induced by spatiotemporal variations and present a general model to characterize the information processing capabilities of the spatiotemporal metasurface. Group theory and abstract number theory are adopted through this investigation, by which the group extension and independent controls of multiple harmonics are proposed and demonstrated as two major tools for information transitions from the spatiotemporal domain to the spectra-wavevector domain. By incorporating Shannon’s entropy theory into the proposed model, we further discover the corresponding information transition efficiencies and the upper bound of the channel capacity of the spatiotemporal metasurface. The results of harmonic information transitions show great potential in achieving high-capacity versatile information processing systems with spatiotemporal metasurfaces.

Highlights

Photonic state transitions, akin to the Stokes Raman effect with inelastic scattering, require phase matching between the initial and final states of electromagnetic waves
We have shown that the harmonic information transitions of spatiotemporal metasurfaces are closely related by the temporal periodicity (L), modulation states (N), harmonic index (m), and temporal repetition factor (u)
Once the number of input phase states and the temporal periodicity of the metasurface are specified, the manipulation of electromagnetic waves can be effectively realized by engineering the spatiotemporal sequences

Summary

Introduction

Akin to the Stokes Raman effect with inelastic scattering, require phase matching between the initial and final states of electromagnetic waves In bulk optics, this can be achieved by perturbing the dielectric constant of the medium with mechanical vibrations or optical excitations[1,2,3]. A number of information-based metasurfaces have been developed, enabling the flexible harvesting of photonic information with self-adaptive radiation formation, neural-networkbased computational imagers, and deep-learning-induced microwave cameras[26,27,28]. Despite these advances, there has been no scheme that provides a fundamental model to study and characterize the information transitions induced by the spatiotemporal metasurface

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