15 research outputs found
Theoretical investigations on Kerr and Faraday rotations in topological multi-Weyl Semimetals
Motivated by the recent proposal of giant Kerr rotation in WSMs, we
investigate the Kerr and Faraday rotations in time-reversal broken multi-Weyl
semimetals (mWSMs) in the absence of an external magnetic field. Using the
framework of Kubo response theory, we find that both the longitudinal and
transverse components of the optical conductivity in mWSMs are modified by the
topological charge (). Engendered by the optical Hall conductivity, we show
in the thin film limit that, while the giant Kerr rotation and corresponding
ellipticity are independent of , the Faraday rotation and its ellipticity
angle scale as and , respectively. In contrast, the polarization
rotation in semi-infinite mWSMs is dominated by the axion field showing
dependence. In particular, the magnitude of Kerr (Faraday) angle decreases
(increases) with increasing in Faraday geometry, whereas in Voigt geometry,
it depicts different -dependencies in different frequency regimes. The
obtained results on the behavior of polarization rotations in mWSMs could be
used in experiments as a probe to distinguish single, double, and triple WSMs,
as well as discriminate the surfaces of mWSMs with and without hosting Fermi
arcs.Comment: 12 Pages, 5 Figures, Submission to SciPos
Radiation families emitted by a discrete soliton in parity-time-symmetric waveguide arrays
We investigate the dynamics of a spatial discrete soliton and the radiation
families emitted by it inside a parity-time ()-symmetric
waveguide array with alternate gain-loss channels. A strong spatial soliton
that evolves inside the waveguide array due to the balance between discrete
diffraction and Kerr nonlinearity excites linear waves in the form of
diffractive radiation when launched with an angle. -symmetric
nature of the waveguide leads to additional radiations in Fourier space that
were never explored before. In our work, we mainly focus on the origin of these
radiations and try to understand how to control them. Under strong
symmetry, a discrete soliton launched normally to the waveguide
array produces strong side-lobes which can lead to a population of field at
in momentum space. In addition, a strong soliton with initial phase
gradient radiates unique symmetry assisted linear wave. We
establish a phase matching condition to locate such radiation in momentum
space. The periodic arrangement of the gain-loss channel also leads to
radiations due to reflection and back-scattering, which is prominent for a weak
soliton. A linear Hamiltonian analysis for such a waveguide array is provided
to identify the -phase transition regime and to optimize the
parameter for stable discrete soliton dynamics. We thoroughly investigate the
origin of all the radiations that emerged in the -symmetric
waveguide array and put forward the background theory which is in good
agreement with the full numerical results
Bistable soliton switching dynamics in a -symmetric coupler with saturable nonlinearity
We investigate the switching dynamics in a -symmetric fiber
coupler composed of a saturable nonlinear material as the core. In such a
saturable nonlinear medium, bistable solitons may evolve due to the balance
between dispersion and saturable nonlinearity, which we extend in the context
of -symmetric coupler. Our investigations of power-controlled and
phase-sensitive switching show richer soliton switching dynamics than the
currently existing conventional counterparts, which may lead to ultrafast and
efficient all-optical switching dynamics at very low power owing to the
combined effects of symmetry and saturable nonlinearity. In
addition to the input power, the relative phase of the input solitons and
saturable coefficient are additional controlling parameters that efficiently
tailor the switching dynamics. Also, we provide a suitable range of system and
pulse parameters that would be helpful for the practical realization of the
coupler to use in all-optical switching devices and photonic circuits.Comment: 7 pages, 9 figure
Plasmon-enhanced circular dichroism spectroscopy of chiral drug solutions
We investigate the potential of surface plasmon polaritons at noble metal
interfaces for surface-enhanced chiroptical sensing of dilute chiral drug
solutions with nano-litre volume. The high quality factor of surface plasmon
resonances in both Otto and Kretschmann configurations enables the enhancement
of circular dichroism thanks to the large near-field intensity of such
plasmonic excitations. Furthermore, the subwavelength confinement of surface
plasmon polaritons is key to attain chiroptical sensitivity to small amounts of
drug volumes placed around 100 nm by the metal surface. Our
calculations focus on reparixin, a pharmaceutical molecule currently used in
clinical studies for patients with community-acquired pneumonia, including
COVID-19 and acute respiratory distress syndrome. Considering realistic dilute
solutions of reparixin dissolved in water with concentration 5 mg/ml and
nl volume, we find a circular-dichroism differential absorption enhancement
factor of the order 20 and chirality-induced polarization distortion
upon surface plasmon polariton excitation. Our results are relevant for the
development of innovative chiroptical sensors capable of measuring the
enantiomeric imbalance of chiral drug solutions with nl volume