10,925 research outputs found
Jaynes Cummings Photonic Superlattices
A classical realization of the Jaynes-Cummings (JC) model, describing the
interaction of a two-level atom with a quantized cavity mode, is proposed based
on light transport in engineered waveguide superlattices. The optical setting
enables to visualize in Fock space dynamical regimes not yet accessible in
quantum systems, providing new physical insights into the deep strong coupling
regime of the JC model. In particular, bouncing of photon number wave packets
in Hilbert space and revivals of populations are explained as generalized Bloch
oscillations in an inhomogeneous tight-binding lattice.Comment: 4 pages, 3 figure
Dynamical trapping of light in modulated waveguide lattices
A discrete analogue of the dynamical (Kapitza) trapping effect, known for
classical and quantum particles in rapidly oscillating potentials, is proposed
for light waves in modulated graded-index waveguide lattices. As in the
non-modulated waveguide lattice a graded-index potential can confine light at
either normal or Bragg angle incidence, periodic modulation of the potential in
the longitudinal direction enables to trap optical beams at both normal and
Bragg incidence angles.Comment: to be published in Optics Letter
Effective magnetic fields for photons in waveguide and coupled resonator lattices
A method to realize effective magnetic fields for photons in square lattices
of coupled optical waveguides or resonators is suggested, which is inspired by
an optical analogue of photon-assisted tunneling of atom optics. It is shown
that an artificial magnetic field can be achieved by application of an index
gradient and periodic lumped phase shifts or modulation of the propagation
constants/resonances, without the need to modulate the coupling strength.Comment: 5 pages, 2 figure
Zak phase of photons in optical waveguide lattices
Zak phase, i.e. the Berry phase acquired during an adiabatic motion of a
Bloch particle across the Brillouin zone, provides a measure of the topological
invariant of Bloch bands in one-dimensional crystalline potentials. Here a
photonic structure, based on engineered lattices of evanescently-coupled
optical waveguides, is proposed to detect Zak phase difference of photons
undergoing Bloch oscillations in topologically distinct Bloch bands of
dimerized superlattices.Comment: 4 figure
Bloch oscillations in non-Hermitian lattices with trajectories in complex plane
Bloch oscillations (BOs), i.e. the oscillatory motion of a quantum particle
in a periodic potential, are one of the most striking effects of coherent
quantum transport in the matter. In the semiclassical picture, it is well known
that BOs can be explained owing to the periodic band structure of the crystal
and the so-called 'acceleration' theorem: since in the momentum space the
particle wave packet drifts with a constant speed without being distorted, in
real space the probability distribution of the particle undergoes a periodic
motion following a trajectory which exactly reproduces the shape of the lattice
band. In non-Hermitian lattices with a complex (i.e. not real) energy band,
extension of the semiclassical model is not intuitive. Here we show that the
acceleration theorem holds for non-Hermitian lattices with a complex energy
band only {\it on average}, and that the periodic wave packet motion of the
particle in the real space is described by a trajectory in {\it complex} plane,
i.e. it generally corresponds to reshaping and breathing of the wave packet in
addition to a transverse oscillatory motion. The concept of BOs involving
complex trajectories is exemplified by considering two examples of
non-Hermitian lattices with a complex band dispersion relation, including the
Hatano-Nelson tight-binding Hamiltonian describing the hopping motion of a
quantum particle on a linear lattice with an imaginary vector potential and a
tight-binding lattice with imaginary hopping rates.Comment: 9 pages, 6 figures, to appear in Phys. Rev.
Exceptional points and photonic catastrophe
Exceptional points (EPs) with a global collapse of pairs of eigenfunctions
are shown to arise in two locally-coupled and spatially-extended optical
structures with balanced gain and loss. Global collapse at the EP deeply
changes light propagation, which becomes very sensitive to small changes of
initial conditions or system parameters, similarly to what happens in models of
classical or quantum catastrophes. The implications of global collapse for
light behavior are illustrated by considering discrete beam diffraction and
Bloch oscillation catastrophe in coupled waveguide lattices.Comment: 5 pages, 4 figure
Convective and absolute PT symmetry breaking in tight-binding lattices
We investigate the onset of parity-time () symmetry breaking in
non-Hermitian tight-binding lattices with spatially-extended loss/gain regions
in presence of an advective term. Similarly to the instability properties of
hydrodynamic open flows, it is shown that symmetry breaking can
be either absolute or convective. In the former case, an initially-localized
wave packet shows a secular growth with time at any given spatial position,
whereas in the latter case the growth is observed in a reference frame moving
at some drift velocity while decay occurs at any fixed spatial position. In the
convective unstable regime, symmetry is restored when the
spatial region of gain/loss in the lattice is limited (rather than extended).
We consider specifically a non-Hermitian extension of the Rice-Mele tight
binding lattice model, and show the existence of a transition from absolute to
convective symmetry breaking when the advective term is large enough. An
extension of the analysis to ac-dc-driven lattices is also presented, and an
optical implementation of the non-Hermitian Rice-Mele model is suggested, which
is based on light transport in an array of evanescently-coupled optical
waveguides with a periodically-bent axis and alternating regions of optical
gain and loss.Comment: 13 pages, 7 figures (to appear in Phys. Rev. A
Synthetic gauge fields for light beams in optical resonators
A method to realize artificial magnetic fields for light waves trapped in
passive optical cavities with anamorphic optical elements is theoretically
proposed. In particular, when a homogeneous magnetic field is realized, a
highly-degenerate Landau level structure for the frequency spectrum of the
transverse resonator modes is obtained, corresponding to a cyclotron motion of
the optical cavity field. This can be probed by transient excitation of the
passive optical resonator.Comment: 5 pages, 4 figure
Supersymmetric transparent optical intersections
Supersymmetric (SUSY) optical structures provide a versatile platform to
manipulate the scattering and localization properties of light, with potential
applications to mode conversion, spatial multiplexing and invisible devices.
Here we show that SUSY can be exploited to realize broadband transparent
intersections between guiding structures in optical networks for both
continuous and discretized light. These include transparent crossing of
high-contrast-index waveguides and directional couplers, as well as crossing of
guiding channels in coupled resonator lattices.Comment: 5 pages, 5 figures, revised version to appear in Optics Letter
Non-Hermitian gauged topological laser arrays
Stable and phase-locked emission in an extended topological supermode of
coupled laser arrays, based on concepts of non-Hermitian and topological
photonics, is theoretically suggested. We consider a non-Hermitian
Su-Schrieffer-Heeger chain of coupled microring resonators and show that
application of a synthetic imaginary gauge field via auxiliary passive
microrings leads to all supermodes of the chain, except one, to become edge
states. The only extended supermode, that retains some topological protection,
can stably oscillate suppressing all other non-topological edge supermodes.
Numerical simulations based on a rate equation model of semiconductor laser
arrays confirm stable anti-phase laser emission in the extended topological
supermode and the role of the synthetic gauge field to enhance laser stability.Comment: 5 figure
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