Localized modes in two-dimensional octagonal-diamond lattices

Two-dimensional octagonal-diamond (OD) atomic lattices have been explored in recent times to study phenomena related to topological phase transitions induced by spin-orbit interaction and gauge fields [1], and magnetic phases and metal-insulator transitions with Hubbard interaction [2, 3]. It can lead to the appearance of nontrivial nearly flat band states with particular topological properties [4]. Here we study the octagonal-diamond photonic lattice formed of linearly coupled waveguides, proposed by [4] as a possible experimental realization of an artificial flat-band system. We investigated analytically and numerically the existence and stability of linear and nonlinear localized modes in a two-dimensional OD lattice. The primitive cell consists of four sites, linearly coupled with each other with the same coupling constant, including two diagonal couplings. The eigenvalue spectrum of the linear lattice consists of two flat bands and two dispersive bands [4]. The upper dispersive band intersects the upper flat band in the middle of the Brillouin zone, as well as the second flat band at the end of the Brillouin zone. In the linear case, there are two types of localized linear solutions, which are composed of eight sites each, having either monomer (+ - + - + - + -) or dimer (+ + - - + + - -) staggered phase structure [4]. In the presence of Kerr nonlinearity, both focusing and defocusing, compacton-like solutions [5] may exhibit instabilities due to intersections of the upper dispersive band and the flat bands. We also discuss the possibility of finding soliton solutions in the frequency gaps occurring between the flat bands and the isolated dispersive bands.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

The influence of nonlinear and linear defects on the light propagation through linear one-dimensional photonic lattice

In this paper, the light beam propagation through one-dimensional photonic lattice, possessing one nonlinear defect and one linear defect, has been investigated numerically. Different dynamical regimes have been identified in terms of the distance between the two defects, position of the incident light beam, the width of linear defect, the values of nonlinearity and presence of the transverse kick. Strong localized modes on the defects, breathing and zig-zag modes in the area between defects have been observed. It has been concluded that the width of the linear defect placed next to the nonlinear one influences localization of the beam at the nonlinear waveguide. On the other hand, the nonlinear defect, regardless of the values of nonlinearity, have a small influence on the beam propagation in photonic lattice. It has been observed that the transverse kick of the initial beam leads to the distortion of localized structures. By launching the light beam towards defects, the reflection of light has been noticed. Presented results can be useful for different applications, such as blocking, filtering and routing of light beam through optical media

Strong coupling regime of semiconductor quantum dot embedded in the nano-cavity

Photonic lattices represent suitable systems for investigation of wave propagation in periodic structures [1]. However, different unavoidable defects may arise either during their process of fabrication or as result of misusage, accidental damage, etc. Although undesirable in the first place, these imperfections enable the existence of different types of stable, localized defect modes [2]. In this paper, we investigate light propagation through composite photonic lattice composed of two identical linear and lossless lattices. The interface between them represents a geometric defect, while each lattice contains a single nonlinear defect that is placed symmetrically with respect to the interface. Depending on the input light beam parameters (its position, width and transverse tilt), the width of geometric defect, strength and position of the nonlinear defects, different dynamical regimes have been identified. These dynamical regimes are caused by the balance of photonic lattice potentials’ contributions originating from the presence of the geometric and two nonlinear defects. We have found numerically conditions under which dynamically stable bounded modes can exist in the area between nonlinear defects or between a nonlinear and a geometric defect. Various types of localized modes such as: two-hump, multi-hump, one- and multicomponent moving breathers localized at a certain area among defects have been observed. The parameters can be adjusted to capture light and to prevent light launched inside the area among defects to leave it, i.e. this corresponds to the appearance of the modes trapped inside this area. Since the configuration of the lattice prevents transmission of the light through the area confined by defects, these modes can formally be related to Fano resonances and Fano- blockade [3, 4]. When light is launched outside the area among defects, different dynamical regimes have been distinguished: total reflection, single and double partial reflection and full transmission through the area among defects. These numerical findings may lead to interesting applications such as blocking, filtering and transporting light beams through the optical medium. Photonic devices based on resonant tunneling such as waveguides interacting through the area between defects, may be applied as add-drop filters.V International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 and the Second international workshop "Control of light and matter waves propagation and localization in photonic lattices" : PHOTONICA2015 : book of abstracts; August 24-28, 2015; Belgrad

The effect of thermal processing on the content and antioxidant capacity of free and bound phenolics of cookies enriched by nettle (Urtica dioica L.) seed flour and extract

The content of free and bound phenolics and their antioxidant capacity in cookies enriched by nettle seed flour and a nettle seed phenolic extract, before, during and after thermal processing (baking at 180°C for 25 min) were examined. The results compare these properties to a cookie obtained only from wheat flour, as the control. Better results were obtained by incorporating nettle seed flour than nettle seed extract. During thermal processing, different changes of phenolic content and antioxidant capacity (increase, decrease or retention) occurred, depending on the form of the phenolics (free or bound), thermal processing time, the cookie and applied antioxidant assays. The free and bound phenolics in the cookie with seed flour were more stable than in the other cookies. At the end of the thermal processing, the cookie with nettle seed flour had a higher content of free and bound phenolics (2.1 and 2.5 times, respectively), and greater antioxidant capacity (the DPPH RSC of free and bound phenolics 9.2 and 4.6 times, and of reducing power 1.6 and 3.4 times, respectively) than the control. There are great possibilities of using nettle seeds in the food industry with the aim of obtaining a functional product with powerful health benefits

Localized modes in two-dimensional “plus” lattice

We have proposed a design of new photonic lattice which does not exist in nature but might be easily fabricated by femtosecond laser inscription technique. The novel two-dimensional photonic lattice comprises of square elementary plaquette inscribed in dodecagon elementary plaquette. Unit cell of the lattice consists of five linearly coupled sites distributed at the edges and in the center of a “plus” sign. Existence and stability of linear and nonlinear localized modes in the uniform and binary “plus” lattice are numerically investigated. The energy spectrum of linear lattice is characterized by a flat band (FB) and four dispersive bands (DB). The FB intersects with two neighboring DBs at four Dirac points at the end of and one in the middle of the Brillouin zone [1]. The lattice binarity provided the opening of gaps between DBs. At the end of the first stage of our study, we can report the existence of FB modes, i.e. compactons, which in the presence of nonlinearity lose the stability owing to the Fano-resonances with the extended states from DBs [2]. In addition, we found a pair of new nonlinear localized mode families in gaps opened by binarity, which could be stable in certain regions of the nonlinearity parameter. The next challenge is related to searching for edge modes and energy transport characteristics in the lattice.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Compactons in two-dimensional octagonal-diamond lattices

XIII Photonics Workshop : Book of abstracts; March 8-12, 2020; Kopaonik, Serbi

Localized modes in a two-dimensional lattice with a pluslike geometry

We investigate analytically and numerically the existence and dynamical stability of different localized modes in a two-dimensional photonic lattice comprising a square plaquette inscribed in the dodecagon lattices. The eigenvalue spectrum of the underlying linear lattice is characterized by a net formed of one flat band and four dispersive bands. By tailoring the intersite coupling coefficient ratio, opening of gaps between two pairs of neighboring dispersive bands can be induced, while the fully degenerate flat band characterized by compact eigenmodes stays nested between two inner dispersive bands. The nonlinearity destabilizes the compact modes and gives rise to unique families of localized modes in the newly opened gaps, as well as in the semi-infinite gaps. The governing mechanism of mode localization in that case is the light energy self-trapping effect. We have shown the stability of a few families of nonlinear modes in gaps. The suggested lattice model may serve for probing various artificial flat-band systems such as ultracold atoms in optical lattices, periodic electronic networks, and polariton condensates

Routing of optical beams by asymmetric defects in (non)linear waveguide arrays

Uniform one-dimensional (1D) nonlinear waveguide array, consisting of parallel, evanescently coupled waveguides represent a special case of 1D photonic crystal [1]. Matured fabrication procedures enable production of arrays whose intrinsic parameters (such as shape and dimensions of the waveguides, coupling strength between them, nonlinear response,…) may be easily changed. The possibility to manipulate light propagation through photonic crystals in a fully controllable fashion, have promise in the field of all-optical communications and photonic devices. However, unavoidable material imperfections, together with slight deviation during fabrication and misusage lead to existence of random defects in the system, which considerably hamper the control of the light flow. These imperfections enable the existence of different types of stable, localized defect modes (breathers and solitons [2]) which may be useful in routing, blocking and filtering of light. Interestingly, various defects may be intentionally inserted in uniform waveguide arrays, enabling studies of defect modes and their influence on light dynamics [3-5]. Interface of two semi-infinite waveguide arrays represent a type of structural (geometric) defect which also can host different localized modes [6, 7]. Recently, the influence of two nonlinear defects on light propagation through linear waveguide array [8] and the steering of discrete breathers in a linear lattice with two nonlinear defects [9] have been explored. Finally, light trapping, reflection and transmission near defect modes in composite linear photonic lattices have been investigated [10]. Here, we studied numerically (by split-step Fourier method) light beam propagation through either uniform of composite 1D (non)linear waveguide arrays having two asymmetric defects, a situation which can be fairly well modeled by the paraxial time-independent Helmholtz equation. Embedded asymmetric defects are either linear or nonlinear. Effects of different positions and widths of asymmetric defects on the light beam propagation have been examined and compared with a case of embedded symmetric defects. Various types of modes localized at these defects and in their vicinity have been found. We also have explored influence of asymmetric defects on tilted beam propagation and identify regimes of trapping, total reflection and transmission of light. Presented results provide an insight into the light beam dynamics in the presence of asymmetrical linear and nonlinear defects and might be useful in several all-optical applications such as filtering and steering of light beams through the optical medium.VI International School and Conference on Photonics and COST actions: MP1406 and MP1402 : PHOTONICA2017 : August 23 - September 1, 2017; Belgrade

Compact localized modes in Dice lattice dressed by artificial flux

XI Conference of the Balkan Physical Union : BPU11; Aug 28 - Sep 1, 2022; BelgradeS07-OP Optics and Photonic

The influence of nonlinear and linear defects on the light propagation through linear one-dimensional photonic lattice

In this paper, the light beam propagation through one-dimensional photonic lattice, possessing one nonlinear defect and one linear defect, has been investigated numerically. Different dynamical regimes have been identified in terms of the distance between the two defects, position of the incident light beam, the width of linear defect, the values of nonlinearity and presence of the transverse kick. Strong localized modes on the defects, breathing and zig-zag modes in the area between defects have been observed. It has been concluded that the width of the linear defect placed next to the nonlinear one influences localization of the beam at the nonlinear waveguide. On the other hand, the nonlinear defect, regardless of the values of nonlinearity, have a small influence on the beam propagation in photonic lattice. It has been observed that the transverse kick of the initial beam leads to the distortion of localized structures. By launching the light beam towards defects, the reflection of light has been noticed. Presented results can be useful for different applications, such as blocking, filtering and routing of light beam through optical media