85 research outputs found
An Equivalent Condition on the Switching Construction of Differentially -uniform Permutations on \gf_{2^{2k}} from the Inverse Function
Differentially -uniform permutations on \gf_{2^{2k}} with high nonlinearity are often chosen as substitution boxes in block ciphers.
Recently, Qu et al. used the powerful switching method to construct permutations with low differential uniformity from the inverse function \cite{QTTL, QTLG} and proposed a sufficient but not necessary condition for these permutations to be differentially -uniform.
In this paper, a sufficient and necessary condition is presented.
We also give a compact estimation for the number of constructed differentially -uniform permutations.
Comparing with those constructions in \cite{QTTL, QTLG}, the number of functions constructed here is much bigger.
As an application, a new class of differentially -uniform permutations is constructed.
The obtained functions in this paper may provide more choices for the design of substitution boxes
Monolithic integration of broadband optical isolators for polarization-diverse silicon photonics
Integrated optical isolators have been a longstanding challenge for photonic
integrated circuits (PIC). An ideal integrated optical isolator for PIC should
be made by a monolithic process, have a small footprint, exhibit broadband and
polarization-diverse operation, and be compatible with multiple materials
platforms. Despite significant progress, the optical isolators reported so far
do not meet all these requirements. In this article we present monolithically
integrated broadband magneto-optical isolators on silicon and silicon nitride
(SiN) platforms operating for both TE and TM modes with record high
performances, fulfilling all the essential characteristics for PIC
applications. In particular, we demonstrate fully-TE broadband isolators by
depositing high quality magneto-optical garnet thin films on the sidewalls of
Si and SiN waveguides, a critical result for applications in TE-polarized
on-chip lasers and amplifiers. This work demonstrates monolithic integration of
high performance optical isolators on chip for polarization-diverse silicon
photonic systems, enabling new pathways to impart nonreciprocal photonic
functionality to a variety of integrated photonic devices
Amorphous photonic topological insulator
Photonic topological insulators (PTIs) exhibit robust photonic edge states
protected by band topology, similar to electronic edge states in topological
band insulators. Standard band theory does not apply to amorphous phases of
matter, which are formed by non-crystalline lattices with no long-range
positional order but only short-range order. Among other interesting
properties, amorphous media exhibit transitions between glassy and liquid
phases, accompanied by dramatic changes in short-range order. Here, we
experimentally investigate amorphous variants of a Chern-number-based PTI. By
tuning the disorder strength in the lattice, we demonstrate that photonic
topological edge states can persist into the amorphous regime, prior to the
glass-to-liquid transition. After the transition to a liquid-like lattice
configuration, the signatures of topological edge states disappear. This
interplay between topology and short-range order in amorphous lattices paves
the way for new classes of non-crystalline topological photonic materials.Comment: 13 pages, 4 figure
Observation of photonic antichiral edge states
Chiral edge states are a hallmark feature of two-dimensional topological
materials. Such states must propagate along the edges of the bulk either
clockwise or counterclockwise, and thus produce oppositely propagating edge
states along the two parallel edges of a strip sample. However, recent theories
have predicted a counterintuitive picture, where the two edge states at the two
parallel strip edges can propagate in the same direction; these anomalous
topological edge states are named as antichiral edge states. Here we report the
experimental observation of antichiral edge states in a gyromagnetic photonic
crystal. The crystal consists of gyromagnetic cylinders in a honeycomb lattice,
with the two triangular sublattices magnetically biased in opposite directions.
With microwave measurement, unique properties of antichiral edge states have
been observed directly, which include the titled dispersion, the chiral-like
robust propagation in samples with certain shapes, and the scattering into
backward bulk states at certain terminations. These results extend and
supplement the current understanding of chiral edge states
Observation of unconventional van der Waals multiferroics near room temperature
The search for two-dimensional (2D) van der Waals (vdW) multiferroics is an
exciting yet challenging endeavor. Room-temperature 2D vdW few-layer
multiferroic is a much bigger insurmountable obstacle. Here we report the
discovery of an unconventional 2D vdW multiferroic with out-of-plane
ferroelectric polarization and long-range magnetic orders in trilayer NiI2
device from 10 K to 295 K. The evolutions of magnetic domains with magnetic
field, and the evolutions between ferroelectric and antiferroelectric phase
have been unambiguously observed. More significantly, we realize a robust
mutual control of magnetism and ferroelectricity at room temperature. The
magnetic domains are manipulated by a small voltage ranging from 1 V to 6 V at
0 T and 295 K. This work opens opportunities for exploring multiferroic physics
at the limit of few atomic layers.Comment: 4 figure
Epitaxial growth of high quality thin films by pulsed laser deposition
Non-collinear antiferromagnet Weyl semimetal have attracted great
research interest recently. Although large anomalous Hall effect, anomalous
Nernst effect and magneto-optical effect have been observed in , most
studies are based on single crystals. So far, it is still challenging to grow
high quality epitaxial thin films with transport and optical
properties comparable to their single crystal counterparts. Here, we report the
structure, magneto-optical and transport properties of epitaxial thin
films fabricated by pulsed laser deposition (PLD). Highly oriented
(0001) and (110) epitaxial films are successfully
growth on single crystalline and MgO substrates. Large anomalous Hall
effect (AHE) up to =3.02 , and
longitudinal magneto-optical Kerr effect (LMOKE) with = 38.1 mdeg at
633 nm wavelength are measured at 300 K temperature, which are comparable to
single crystals. Our work demonstrates that high quality
epitaxial thin films can be fabricated by PLD, paving the way for future device
applications
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