Electromagnetic Spatiotemporal Differentiation Meta-Devices

Spatiotemporal optical computing devices that can 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, an analog spatiotemporal differentiator in microwaves based on an asymmetrical metasurface that has a phase singularity in the spatiotemporal domain is experimentally demonstrated. It is shown that this structure can 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 is performed utilizing a metallic slit, and the temporal differentiation capability of the device is examined by Gaussian-like temporal pulses of different widths. It is further confirmed that the differentiator demonstrated here can detect sharp changes in spatiotemporal pulses even with intricate profiles and theoretically estimated the resolution limits of the spatial and temporal edge detection. It is also shown that the pulse input after passing the spatiotemporal differentiator implemented here could carry a transverse orbital angular momentum (OAM) with a fractal topology charge. An analog spatiotemporal differentiator in microwaves based on the asymmetric grating-type metasurface is experimentally realized. Leveraging the unidirectional excitation of spoof surface plasmon polaritons, the transfer function required by an ideal first-order spatiotemporal differentiator is achieved, which is verified theoretically and experimentally. The experimental results prove the spatial edge detection and temporal differentiation functions of meta-devices.image