Ana Radosavljević

Light propagation management by disorder and nonlinearity in one-dimensional photonic lattices

We study managing of light beam propagation by competing disorder and nonlinearity in one-dimensional disordered, nonlinear photonic lattices (PLs). The system is modeled by a paraxial time-independent Helmholtz equation, which includes the nonlinear saturable self-interacting term and the quenched or nonquenched disordered PL potential. Diverse PL structures with alternating length of the regular and disordered parts are investigated showing the possibility to change the light propagation from ballistic to the propagation of the transversely localized structures originating from the Anderson-like localization or self-trapping mechanism. Dynamical calculations indicate the possibility of guiding light through the lattice by proper lattice management.

Control of light propagation in one-dimensional quasi-periodic nonlinear photonic lattices

We investigate light localization in quasi-periodic nonlinear photonic lattices (PLs) composed of two periodic component lattices of equal lattice potential strength and incommensurate spatial periods. By including the system parameters from the experimentally realizable setup, we confirm that the light localization is a threshold determined phenomenon in a limit of negligible nonlinearity. In addition, we show that self-trapping can affect the localized light in the established setup only in the presence of strong nonlinearity. Guided by these findings we consider the possibility of governing light propagation by proposing a composite lattice system comprising alternating quasi-periodic parts with different potential depths and nonlinearity strengths.

Defect induced wave-packet dynamics in linear one-dimensional photonic lattices

We study numerically light beam propagation across uniform, linear, one-dimensional photonic lattice possessing one nonlinear defect. Depending on the strength of nonlinear defect, input beam position and phase shift, different dynamical regimes have been identified. We distinguish input parameters set for which a regime of light propagation blockade by the nonlinear defect appears. Obtained results may be useful for all-optical control of transmission of waves in interferometry.

Coherent light propagation through multicore optical fibers with linearly coupled cores

Multicore fibers with linearly coupled cores are considered as a means of the coherent transport needed for high-capacity communication systems and high-power fiber lasers. The conditions of the existence and stability of coherent light propagation in multicore fibers with circularly arranged cores are derived. The multicore fiber is modeled by the linear discrete complex Ginzburg–Landau equation, while its eigenvalues are found analytically. The inverse eigenvalue problem proposing the commensurability of eigenvalues is solved to find the intercore coupling coefficients that support periodic revivals of the input state. Both planar modes and vortices are considered. Effects of the central core and material loss/gain on eigenvalue commensurability conditions and mode dynamics are studied in detail.

Models of spin-orbit-coupled oligomers

We address the stability and dynamics of eigenmodes in linearly shaped strings (dimers, trimers, tetramers, and pentamers) built of droplets in a binary Bose-Einstein condensate (BEC). The binary BEC is composed of atoms in two pseudo-spin states with attractive interactions, dressed by properly arranged laser fields, which induce the (pseudo-) spin-orbit (SO) coupling. We demonstrate that the SO-coupling terms help to create eigenmodes of particular types in the strings. Dimer, trimer, and pentamer eigenmodes of the linear system, which correspond to the zero eigenvalue (EV, alias chemical potential) extend into the nonlinear ones, keeping an exact analytical form, while tetramers do not admit such a continuation, because the respective spectrum does not contain a zero EV. Stability areas of these modes shrink with the increasing nonlinearity. Besides these modes, other types of nonlinear states, which are produced by the continuation of their linear counterparts corresponding to some nonzero EVs, are found in a numerical form (including ones for the tetramer system). They are stable in nearly entire existence regions in trimer and pentamer systems, but only in a very small area for the tetramers. Similar results are also obtained, but not displayed in detail, for hexa- and septamers.

Light propagation management in complex photonic lattices

Here, an overview of the main results for light propagation and control over it in composite complex photonic lattices based on photorefractive materials is presented.

Optimization of planar nanostructures based on cubic GaN/AlGaN for applications in the IR spectral range by Genetic Algorithm

A method is proposed for the structural parameters optimization of various planar-type nanostructures, intended for detection of IR radiation, based on the Genetic Algorithm for global optimization. Quantum well profile is considered for maximization of the quantum Stark effect and its application to tunable mid-infrared photodetectors, while in case of perturbed superlattices we utilize the above-the-barrier confined states, in order to extend the range of transition energies towards near IR part of the spectrum, i.e. communication wavelengths. Among the structural profiles which provide the predefined central transition energies, only those with maximal absorption are selected. The effects of band nonparabolicity are taken into account.