TY  - JOUR
AU  - Ivanović, Marija D.
AU  - Mančić, Ana
AU  - Hermann-Avigliano, Carla
AU  - Hadžievski, Ljupčo
AU  - Maluckov, Aleksandra
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8837
AB  - In this paper, we establish a new scheme for identification and classification of high intensity events generated by the propagation of light through a photorefractive SBN crystal. Among these events, which are the inevitable consequence of the development of modulation instability, are speckling and soliton-like patterns. The usual classifiers, developed on statistical measures, such as the significant intensity, often provide only a partial characterization of these events. Here, we try to overcome this deficiency by implementing the convolution neural network method to relate experimental data of light intensity distribution and corresponding numerical outputs with different high intensity regimes. The train and test sets are formed of experimentally obtained intensity profiles at the crystal output facet and corresponding numerical profiles. The accuracy of detection of speckles reaches maximum value of 100%, while the accuracy of solitons and caustic detection is above 97%. These performances are promising for the creation of neural network based routines for prediction of extreme events in wave media. © 2020 IOP Publishing Ltd.
T2  - Journal of Optics
T1  - Deep learning-based classification of high intensity light patterns in photorefractive crystals
VL  - 22
IS  - 3
SP  - 035504
DO  - 10.1088/2040-8986/ab70f0
ER  - 

@article{
author = "Ivanović, Marija D. and Mančić, Ana and Hermann-Avigliano, Carla and Hadžievski, Ljupčo and Maluckov, Aleksandra",
year = "2020",
abstract = "In this paper, we establish a new scheme for identification and classification of high intensity events generated by the propagation of light through a photorefractive SBN crystal. Among these events, which are the inevitable consequence of the development of modulation instability, are speckling and soliton-like patterns. The usual classifiers, developed on statistical measures, such as the significant intensity, often provide only a partial characterization of these events. Here, we try to overcome this deficiency by implementing the convolution neural network method to relate experimental data of light intensity distribution and corresponding numerical outputs with different high intensity regimes. The train and test sets are formed of experimentally obtained intensity profiles at the crystal output facet and corresponding numerical profiles. The accuracy of detection of speckles reaches maximum value of 100%, while the accuracy of solitons and caustic detection is above 97%. These performances are promising for the creation of neural network based routines for prediction of extreme events in wave media. © 2020 IOP Publishing Ltd.",
journal = "Journal of Optics",
title = "Deep learning-based classification of high intensity light patterns in photorefractive crystals",
volume = "22",
number = "3",
pages = "035504",
doi = "10.1088/2040-8986/ab70f0"
}

Ivanović, M. D., Mančić, A., Hermann-Avigliano, C., Hadžievski, L.,& Maluckov, A.. (2020). Deep learning-based classification of high intensity light patterns in photorefractive crystals. in Journal of Optics, 22(3), 035504.
https://doi.org/10.1088/2040-8986/ab70f0

Ivanović MD, Mančić A, Hermann-Avigliano C, Hadžievski L, Maluckov A. Deep learning-based classification of high intensity light patterns in photorefractive crystals. in Journal of Optics. 2020;22(3):035504.
doi:10.1088/2040-8986/ab70f0 .

Ivanović, Marija D., Mančić, Ana, Hermann-Avigliano, Carla, Hadžievski, Ljupčo, Maluckov, Aleksandra, "Deep learning-based classification of high intensity light patterns in photorefractive crystals" in Journal of Optics, 22, no. 3 (2020):035504,
https://doi.org/10.1088/2040-8986/ab70f0 . .

TY  - JOUR
AU  - Stojanović, Mirjana G.
AU  - Stojanović Krasić, Marija
AU  - Maluckov, Aleksandra
AU  - Johansson, Magnus M.
AU  - Salinas, I. A.
AU  - Vicencio, Rodrigo A.
AU  - Stepić, Milutin
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/9664
AB  - We consider a two-dimensional octagonal-diamond network with a fine-tuned diagonal coupling inside the diamond-shaped unit cell. Its linear spectrum exhibits coexistence of two dispersive bands (DBs) and two flat bands (FBs), touching one of the DBs embedded between them. Analogous to the kagome lattice, one of the FBs will constitute the ground state of the system for a proper sign choice of the Hamiltonian. The system is characterized by two different flat-band fundamental octagonal compactons, originating from the destructive interference of fully geometric nature. In the presence of a nonlinear amplitude (on-site) perturbation, the single-octagon linear modes continue into one-parameter families of nonlinear compact modes with the same amplitude and phase structure. However, numerical stability analysis indicates that all strictly compact nonlinear modes are unstable, either purely exponentially or with oscillatory instabilities, for weak and intermediate nonlinearities and sufficiently large system sizes. Stabilization may appear in certain ranges for finite systems and, for the compacton originating from the band at the spectral edge, also in a regime of very large focusing nonlinearities. In contrast to the kagome lattice, the latter compacton family will become unstable already for arbitrarily weak defocusing nonlinearity for large enough systems. We show analytically the existence of a critical system size consisting of 12 octagon rings, such that the ground state for weak defocusing nonlinearity is a stable single compacton for smaller systems, and a continuation of a nontrivial, noncompact linear combination of single compacton modes for larger systems. Investigating generally the different nonlinear localized (noncompact) mode families in the semi-infinite gap bounded by this FB, we find that, for increasing (defocusing) nonlinearity the stable ground state will continuously develop into an exponentially localized mode with two main peaks in antiphase. At a critical nonlinearity strength a symmetry-breaking pitchfork bifurcation appears, so that the stable ground state is single peaked for larger defocusing nonlinearities. We also investigate numerically the mobility of localized modes in this regime and find that the considered modes are generally immobile both with respect to axial and diagonal phase-gradient perturbations.
T2  - Physical Review A
T1  - Localized modes in linear and nonlinear octagonal-diamond lattices with two flat bands
VL  - 102
IS  - 2
SP  - 023532
DO  - 10.1103/PhysRevA.102.023532
ER  - 

@article{
author = "Stojanović, Mirjana G. and Stojanović Krasić, Marija and Maluckov, Aleksandra and Johansson, Magnus M. and Salinas, I. A. and Vicencio, Rodrigo A. and Stepić, Milutin",
year = "2020",
abstract = "We consider a two-dimensional octagonal-diamond network with a fine-tuned diagonal coupling inside the diamond-shaped unit cell. Its linear spectrum exhibits coexistence of two dispersive bands (DBs) and two flat bands (FBs), touching one of the DBs embedded between them. Analogous to the kagome lattice, one of the FBs will constitute the ground state of the system for a proper sign choice of the Hamiltonian. The system is characterized by two different flat-band fundamental octagonal compactons, originating from the destructive interference of fully geometric nature. In the presence of a nonlinear amplitude (on-site) perturbation, the single-octagon linear modes continue into one-parameter families of nonlinear compact modes with the same amplitude and phase structure. However, numerical stability analysis indicates that all strictly compact nonlinear modes are unstable, either purely exponentially or with oscillatory instabilities, for weak and intermediate nonlinearities and sufficiently large system sizes. Stabilization may appear in certain ranges for finite systems and, for the compacton originating from the band at the spectral edge, also in a regime of very large focusing nonlinearities. In contrast to the kagome lattice, the latter compacton family will become unstable already for arbitrarily weak defocusing nonlinearity for large enough systems. We show analytically the existence of a critical system size consisting of 12 octagon rings, such that the ground state for weak defocusing nonlinearity is a stable single compacton for smaller systems, and a continuation of a nontrivial, noncompact linear combination of single compacton modes for larger systems. Investigating generally the different nonlinear localized (noncompact) mode families in the semi-infinite gap bounded by this FB, we find that, for increasing (defocusing) nonlinearity the stable ground state will continuously develop into an exponentially localized mode with two main peaks in antiphase. At a critical nonlinearity strength a symmetry-breaking pitchfork bifurcation appears, so that the stable ground state is single peaked for larger defocusing nonlinearities. We also investigate numerically the mobility of localized modes in this regime and find that the considered modes are generally immobile both with respect to axial and diagonal phase-gradient perturbations.",
journal = "Physical Review A",
title = "Localized modes in linear and nonlinear octagonal-diamond lattices with two flat bands",
volume = "102",
number = "2",
pages = "023532",
doi = "10.1103/PhysRevA.102.023532"
}

Stojanović, M. G., Stojanović Krasić, M., Maluckov, A., Johansson, M. M., Salinas, I. A., Vicencio, R. A.,& Stepić, M.. (2020). Localized modes in linear and nonlinear octagonal-diamond lattices with two flat bands. in Physical Review A, 102(2), 023532.
https://doi.org/10.1103/PhysRevA.102.023532

Stojanović MG, Stojanović Krasić M, Maluckov A, Johansson MM, Salinas IA, Vicencio RA, Stepić M. Localized modes in linear and nonlinear octagonal-diamond lattices with two flat bands. in Physical Review A. 2020;102(2):023532.
doi:10.1103/PhysRevA.102.023532 .

Stojanović, Mirjana G., Stojanović Krasić, Marija, Maluckov, Aleksandra, Johansson, Magnus M., Salinas, I. A., Vicencio, Rodrigo A., Stepić, Milutin, "Localized modes in linear and nonlinear octagonal-diamond lattices with two flat bands" in Physical Review A, 102, no. 2 (2020):023532,
https://doi.org/10.1103/PhysRevA.102.023532 . .