Electromagnetic Spatiotemporal Differentiators

TL;DR

This paper demonstrates an innovative microwave-based spatiotemporal differentiator using an asymmetrical metasurface, capable of real-time edge detection and enhancing information encoding through orbital angular momentum.

Contribution

It introduces a novel asymmetrical metasurface design for microwave spatiotemporal differentiation, enabling compact, integrated, and real-time optical computing functionalities.

Findings

Successfully performed spatial edge detection using a metallic slit.

Demonstrated temporal differentiation with Gaussian-like pulses.

Confirmed ability to detect sharp spatiotemporal changes and encode orbital angular momentum.

Abstract

Spatiotemporal optical computing devices which could perform mathematical operations in both spatial and temporal domains can provide unprecedented measures to build efficient and real-time information processing systems. It is particularly important to realize the comprehensive functions in a compact design for better integration with electronic components. In this work, we experimentally demonstrated an analogue spatiotemporal differentiator in microwaves based on an asymmetrical metasurface which has a phase singularity in the spatiotemporal domain. We showed that this structure could give rise to a spatiotemporal transfer function required by an ideal first-order differentiator in both spatial and temporal domains by tailoring the unidirectional excitation of spoof surface plasmon polaritons (SSPPs). The spatial edge detection was performed utilizing a metallic slit and the temporal differentiation capability of the device was examined by Gaussian-like temporal pulses of different width. We further confirmed the differentiator demonstrated here could detect sharp changes of spatiotemporal pulses even with intricate profiles and theoretically estimated the resolution limits of the spatial and temporal edge detection. We also show that the pulse input after passing the spatiotemporal differentiator implemented here could carry a transverse orbital angular momentum (OAM) with a fractal topology charge which further increases the information quantity.