483 research outputs found
Relation between the autocorrelation and Wigner functions
We show a simple mechanism to measure the Wigner function of a harmonic
oscillator. For this system we also show that autocorrelation and Wigner
functions are equivalent.Comment: Modified title and slightly modified version from the one publishe
Supersymmetry-generated complex optical potentials with real spectra
We show that the formalism of supersymmetry (SUSY), when applied to
parity-time (PT) symmetric optical potentials, can give rise to novel
refractive index landscapes with altogether non-trivial properties. In
particular, we find that the presence of gain and loss allows for arbitrarily
removing bound states from the spectrum of a structure. This is in stark
contrast to the Hermitian case, where the SUSY formalism can only address the
fundamental mode of a potential. Subsequently we investigate isospectral
families of complex potentials that exhibit entirely real spectra, despite the
fact that their shapes violate PT-symmetry. Finally, the role of SUSY
transformations in the regime of spontaneously broken PT symmetry is
investigated.Comment: 6 pages, 4 figure
Exact bidirectional X-wave solutions in fiber Bragg gratings
We find exact solutions describing bidirectional pulses propagating in fiber
Bragg gratings. They are derived by solving the coupled-mode theory equations
and are expressed in terms of products of modified Bessel functions with
algebraic functions. Depending on the values of the two free parameters the
general bidirectional X-wave solution can also take the form of a
unidirectional pulse. We analyze the symmetries and the asymptotic properties
of the solutions and also discuss about additional waveforms that are obtained
by interference of more than one solutions. Depending on their parameters such
pulses can create a sharp focus with high contrast
Negative index Clarricoats-Waldron waveguides for terahertz and far infrared applications
We explore a class of dielectrically loaded metallic waveguides capable of supporting negative index modes in the far infrared and terahertz regime. Principles of operation, modal structure and appropriate coupling schemes are analytically and numerically investigated. The extreme simplicity of the proposed design, along with the non-conventional and counter intuitive electromagnetic properties of this family of waveguides, makes these structures excellent candidates for the practical realization of negative index far infrared and terahertz devices with new and interesting functionalities. Generalizations and extensions of the suggested design are also discussed
Bessel-like optical beams with arbitrary trajectories
A method is proposed for generating Bessel-like optical beams with arbitrary trajectories in free space. The method involves phase-modulating an optical wavefront so that conical bundles of rays are formed whose apexes write a continuous focal curve with prespecified shape. These ray cones have circular bases on the input plane, thus their interference results in a Bessel-like transverse field profile that propagates along the specified trajectory with a remarkably invariant main lobe. Such beams can be useful as hybrids between nonaccelerating and accelerating optical waves that share diffraction-resisting and self-healing properties
Advanced trajectory engineering of diffraction-resisting laser beams
We introduce an analytical technique for engineering the trajectory of diffraction-resisting laser beams. The generated beams have a Bessel-like transverse field distribution and can be navigated along rather arbitrary curved paths in free space, thus being an advanced hybrid between accelerating and non-accelerating diffraction-free optical waves. The method involves phase-modulating the wavefront of a Gaussian laser beam to create a continuum of conical ray bundles whose apexes define a prespecified focal curve, along which a nearly perfect circular intensity lobe propagates without diffracting. Through extensive numerical simulations, we demonstrate the great flexibility in the design of a gamut of different beam trajectories. Propagation around obstructions and self-healing scenarios are also investigated. The proposed wave entities can be used extensively for light trajectory control in applications such as laser microfabrication, optical tweezers and curved plasma filamentation spectroscopy
Scattering in and Symmetric Multimode Waveguides: Generalized Conservation Laws and Spontaneous Symmetry Breaking beyond One Dimension
We extend the generalize conservation law of light propagating in a
one-dimensional -symmetric system, i.e., for the
transmittance and the reflectance from the left and right, to a
multimode waveguide with either or symmetry, in which
higher dimensional investigations are necessary. These conservation laws exist
not only in a matrix form for the transmission and reflection matrices; they
also exist in a scalar form for real-valued quantities by defining generalized
transmittance and reflectance. We then discuss, for the first time, how a
multimode -symmetric waveguide can be used to observe spontaneous
symmetry breaking of the scattering matrix, which typically requires tuning the
non-hermiticity of the system (i.e. the strength of gain and loss). Here the
advantage of using a multimode waveguide is the elimination of tuning any
system parameters: the transverse mode order plays the role of the symmetry
breaking parameter, and one observes the symmetry breaking by simply performing
scattering experiment in each waveguide channel at a single frequency and fixed
strength of gain and loss.Comment: 8 pages, 6 figure
Discrete Ginzburg-Landau solitons
We demonstrate that discrete solitons are possible in Ginzburg-Landau lattices. As a result of discreteness, we find that this system exhibits a host of features that have no counterpart whatsoever in either the continuous limit or in other conservative discrete models
Discrete solitons and soliton-induced dislocations in partially-coherent photonic lattices
We investigate the interaction between a light beam and a two-dimensional
photonic lattice that is photo-induced in a photorefractive crystal using
partially coherent light. We demonstrate that this interaction process is
associated with a host of new phenomena including lattice dislocation, lattice
deformation, and creation of structures akin to optical polarons. In addition,
two-dimensional discrete solitons are realized in such partially coherent
photonic lattices.Comment: 12 pages, 4 figures (revised). accepted by Phys. Rev. Let
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