835 research outputs found
Local orbital-angular-momentum dependent surface states with topological protection
Chiral surface states along the zigzag edge of a valley photonic crystal in
the honeycomb lattice are demonstrated. By decomposing the local fields into
orbital angular momentum (OAM) modes, we find that the chiral surface states
present OAM-dependent unidirectional propagation characteristics. Particularly,
the propagation directivities of the surface states are quantified by the local
OAM decomposition and are found to depend on the chiralities of both the source
and surface states. These findings allow for the engineering control of the
unidirectional propagation of electromagnetic energy without requiring an
ancillary cladding layer. Furthermore, we examine the propagation of the chiral
surface states against sharp bends. It turns out that although only certain
states successfully pass through the bend, the unidirectional propagation is
well maintained due to the topology of the structure.Comment: 9 pages, 6 figure
Investigating Spatial Interdependence in E-Bike Choice Using Spatially Autoregressive Model
Increased attention has been given to promoting e-bike usage in recent years. However, the research gap still exists in understanding the effects of spatial interdependence on e-bike choice. This study investigated how spatial interdependence affected the e-bike choice. The Moran’s I statistic test showed that spatial interdependence exists in e-bike choice at aggregated level. Bayesian spatial autoregressive logistic analyses were then used to investigate the spatial interdependence at individual level. Separate models were developed for commuting and non-commuting trips. The factors affecting e-bike choice are different between commuting and non-commuting trips. Spatial interdependence exists at both origin and destination sides of commuting and non-commuting trips. Travellers are more likely to choose e-bikes if their neighbours at the trip origin and destination also travel by e-bikes. And the magnitude of this spatial interdependence is different across various traffic analysis zones. The results suggest that, without considering spatial interdependence, the traditional methods may have biased estimation results and make systematic forecasting errors.</p
A brief review of topological photonics in one, two, and three dimensions
Topological photonics has attracted increasing attention in recent years due
to the unique opportunities it provides to manipulate light in a robust way
immune to disorder and defects. Up to now, diverse photonic platforms, rich
physical mechanisms and fruitful device applications have been proposed for
topological photonics, including one-way waveguide, topological lasing,
topological nanocavity, Dirac and Weyl points, Fermi arcs, nodal lines, etc. In
this review, we provide an introduction to the field of topological photonics
through the lens of topological invariants and bulk-boundary correspondence in
one, two, and three dimensions, which may not only offer a unified
understanding about the underlying robustness of diverse and distinct
topological phenomena of light, but could also inspire further developments by
introducing new topological invariants and unconventional bulk-boundary
correspondence to the research of topological photonics.Comment: 29 pages, 12 figures, 341 reference
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