44 research outputs found
Electromagnetic Spatiotemporal Differentiators
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.Comment: 6 figure
Constraining the interacting dark energy models from weak gravity conjecture and recent observations
We examine the effectiveness of the weak gravity conjecture in constraining
the dark energy by comparing with observations. For general dark energy models
with plausible phenomenological interactions between dark sectors, we find that
although the weak gravity conjecture can constrain the dark energy, the
constraint is looser than that from the observations.Comment: 14 pages, 12 figures, revtex4, v2: minor corrections, accepted for
publication in PL