Bragg scattering of stochastic beams in PT-symmetric photonic lattices.

The propagation of a Gaussian-Schell beam through a PT-symmetric optical lattice, whose index of refraction is represented by a sinusoidal type of function, is theoretically investigated. Within the framework of standard coherence theory, one is able to access and elucidate unexpected consequences of the interplay between the spatial coherence properties of the beam and the non-Hermitian nature of the photonic lattice. We describe how one may use a non-Hermitian periodic medium to enhance the spatial coherence properties of a partially coherent beam.

Optics in South America: introduction.

South American optics research has seen remarkable growth over the past 50 years, with significant contributions in areas such as quantum optics, holography, spectroscopy, nonlinear optics, statistical optics, nanophotonics and integrated photonics. The research has driven economic development in sectors like telecom, biophotonics, biometrics, and agri-sensing. This joint feature issue between JOSA A and JOSA B exhibits cutting-edge optics research from the region, fostering a sense of community and promoting collaboration among researchers.

Low coherence-induced resonance in double-layer structures having parity-time symmetry.

We derive simple formulas for the transmittance and reflectance of Gaussian-Schell beams incident upon any stratified dielectric structure by using second-order classical coherence theory in the space-frequency picture. The formalism is applied to a particular structure consisting of a double layer, with balanced gain and loss, satisfying parity-time symmetry conditions. It is shown that sources with a low degree of spatial coherence, on the order of the wavelength, can induce large resonant peaks in the transmitted and reflected amplitudes.

Non-Hermitian spectral changes in the scattering of partially coherent radiation by periodic structures.

The physical aspects of partially coherent radiation interacting with deterministic non-Hermitian periodic materials remain largely unexplored in the statistical optics literature. Here, we consider the scattering of partially coherent radiation by a deterministic periodic medium, symmetric under the simultaneous transformations of parity inversion and time reversal, i.e.

Non-Bragg-gap solitons in one-dimensional Kerr-metamaterial Fibonacci heterostructures.

A detailed study of non-Bragg-gap solitons in one-dimensional Kerr-metamaterial quasiperiodic Fibonacci heterostructures is performed. The transmission coefficient is numerically obtained by combining the transfer-matrix formalism in the metamaterial layers with a numerical solution of the nonlinear differential equation in the Kerr slabs, and by considering the loss effects in the metamaterial slabs. A switching from states of no transparency in the linear regime to high-transparency states in the nonlinear regime is observed for both zero-order and plasmon-polariton gaps.

Metric-signature topological transitions in dispersive metamaterials.

The metric signature topological transitions associated with the propagation of electromagnetic waves in a dispersive metamaterial with frequency-dependent and anisotropic dielectric and magnetic responses are examined in the present work. The components of the reciprocal-space metric tensor depend upon both the electric permittivity and magnetic permeability of the metamaterial, which are taken as Drude-like dispersive models. A thorough study of the frequency dependence of the metric tensor is presented which leads to the possibility of topological transitions of the isofrequency surface determining the wave dynamics inside the medium, to a diverging photonic density of states at some range of frequencies, and to the existence of large wave vectors' modes propagating through the metamaterial.

Bulk plasmon polariton-gap soliton-induced transparency in one-dimensional Kerr-metamaterial superlattices.

We have performed a theoretical study of various arrangements of one-dimensional heterostructures composed by bilayers made of nondispersive (A)/dispersive linear (B) materials and illuminated by an obliquely incident electromagnetic wave, which are shown to exhibit a robust bulk-like plasmon-polariton gap for frequencies below the plasma frequency. The origin of this gap stems from the coupling between photonic and plasmonic modes that may be of a magnetic (electric) origin in a transversal electric (traversal magnetic) configuration yielding a plasmon-polariton mode. By substituting the nondispersive linear layer by a nonlinear Kerr layer, we have found that, for frequencies close to the edge of the plasmon-polariton gap, the transmission of a finite superlattice presents a multistable behavior and it switches from very low values to the maximum transparency at particular values of the incident power.

Optical spin-to-orbital plasmonic angular momentum conversion in subwavelength apertures.

Within the framework of the Huygens-Fresnel approach, we evaluate the coherent superposition of surface plasmon (SP) modes excited by an incident circularly polarized light propagating through an array of subwavelength holes. Numerical results of the plasmonic distribution exhibit a rich structure that reveals the creation and annihilation of vortex arrays in the field phase. These phase singularities stem from total transfer of the spin angular momentum (AM) of the incident radiation to the orbital AM of the SP.

Omnidirectional suppression of Anderson localization of light in disordered one-dimensional photonic superlattices.

The omnidirectional suppression of Anderson localization of light in a disordered one-dimensional normal-metamaterial photonic superlattice is thoroughly investigated. Analytical conditions relating to the electric-permittivity and magnetic-permeability responses of each slab of the heterostructure are established for the omnidirectional divergence of the localization length of the normal-metamaterial superlattice. The robustness of such conditions with respect to the degree of disorder of the superlattice is also analyzed.

Field profiles of bulk plasmon polariton modes in layered systems containing a metamaterial.

Electric and magnetic fields in a one-dimensional layered system that alternates air and a metamaterial are investigated. Special attention is devoted to frequencies of electric and magnetic bulk plasmons. It is shown that plasmon polaritons nearby such frequencies display field profiles concentrated in the metamaterial, where the field component parallel to the stacking direction is essentially uniform and dominates the perpendicular one.

Anderson localization and Brewster anomalies in photonic disordered quasiperiodic lattices.

A comprehensive study of the properties of light propagation through one-dimensional photonic disordered quasiperiodic superlattices, composed of alternating layers with random thicknesses of air and a dispersive metamaterial, is theoretically performed. The superlattices consist of the successive stacking of N quasiperiodic Fibonacci or Thue-Morse heterostructures. The width of the slabs in the photonic superlattice may randomly fluctuate around its mean value, which introduces a structural disorder into the system.

Absorption effects on plasmon polaritons in quasiperiodic photonic superlattices containing a metamaterial.

Absorption effects on plasmon-polariton excitations in quasiperiodic (Fibonacci and Thue-Morse) one-dimensional stacks composed of layers of right- and left-handed materials are theoretically investigated. A Drude-type dispersive response for both the dielectric permittivity and magnetic permeability of the left-handed layer is considered. Maxwell's equations are solved for oblique incidence by using the transfer matrix formalism, and the reflection coefficient as a function of the frequency and incidence angle is obtained.

Plasmon polaritons in photonic metamaterial superlattices: absorption effects.

We discuss the propagation of electromagnetic waves in layered structures made up of alternate layers of air and metamaterials. The role played by absorption on the existence of electric and magnetic plasmon polaritons is investigated. Results show that plasmon-polariton modes are robust even in the presence of rather large absorption.

Non-Markovian damping of Rabi oscillations in semiconductor quantum dots.

A systematic investigation is performed on the damping of Rabi oscillations induced by an external electromagnetic field interacting with a two-level semiconductor system. We have considered a coherently driven two-level system coupled to a dephasing reservoir and shown that, to explain the dependence of the dephasing rate on the driving intensity, it is essential to consider the non-Markovian character of the reservoir. Moreover, we have demonstrated that intensity-dependent damping may be induced by various dephasing mechanisms due to stationary as well as non-stationary effects caused by coupling with the environment.

Driving-dependent damping of Rabi oscillations in two-level semiconductor systems.

We propose a mechanism to explain the nature of the damping of Rabi oscillations with an increasing driving-pulse area in localized semiconductor systems and have suggested a general approach which describes a coherently driven two-level system interacting with a dephasing reservoir. Present calculations show that the non-Markovian character of the reservoir leads to the dependence of the dephasing rate on the driving-field intensity, as observed experimentally. Moreover, we have shown that the damping of Rabi oscillations might occur as a result of different dephasing mechanisms for both stationary and nonstationary effects due to coupling to the environment.

Photonic band structure and symmetry properties of electromagnetic modes in photonic crystals.

Within the Maxwell framework and using a transfer-matrix technique we have determined a general equation which governs the photonic band structure and the density of states of one-dimensional superlattices composed of two alternate layers characterized by different refractive indexes, which may take on positive as well as negative values. Besides the usual well-known results, we have found null-gap points for commensurate values of the optical path lengths of each layer. Furthermore, we have been able to characterize non-Bragg gaps that show up in frequency regions in which the average refractive index is null.

Resonant Zener tunneling in two-dimensional periodic photonic lattices.

We study Zener tunneling in two-dimensional photonic lattices and derive, for the case of hexagonal symmetry, the generalized Landau-Zener-Majorana model describing resonant interaction between high-symmetry points of the photonic spectral bands. We demonstrate that this effect can be employed for the generation of Floquet-Bloch modes and verify the model by direct numerical simulations of the tunneling effect.

Zener tunneling in two-dimensional photonic lattices.

We discuss the interband light tunneling in a two-dimensional periodic photonic structure, as studied recently in experiments for optically induced photonic lattices [Trompeter, Phys. Rev. Lett.

Soliton propagation in a medium with Kerr nonlinearity and resonant impurities: a variational approach.

Using a variational approach we have studied the shape preserving coherent propagation of light pulses in a resonant dispersive medium in the presence of the Kerr nonlinearity. Within the framework of a combined nonintegrable system composed of one nonlinear Schrödinger and a pair of Bloch equations, we show the existence of a solitary wave. We have tested our analytical solution through numerical simulations confirming its solitary wave nature.

Coherent interaction effects in pulses propagating through a doped nonlinear dispersive medium.

Using a numerical approach we report on the cloning dynamics of simultaneous self-induced transparency (SIT) and nonlinear Schrödinger (NLS) solitons in a doped nonlinear dispersive medium. This technique involves a three-level atomic system interacting resonantly with two optical fields within a Lambda scheme. As a result, a pulse in the signal frequency is transformed into a replica of the pulse in the pump frequency.

Soliton interaction in a nonlinear waveguide in the presence of resonances.

The simultaneous propagation of two optical pulses through a nonlinear dispersive medium composed of a resonant three-level system is investigated. By choosing a soliton of area 4 pi and order N=2 at the pump frequency, together with a weaker pulse with a sech profile at the signal frequency, we show that the pump soliton breaks up into a pair of solitary waves which are cloned to the signal frequency. Due to a combination of coherent population trapping and nonlinear dispersive effects, the pair interacts in a repulsive fashion so that the taller wave travels faster than the shorter one.