Photonic molecule state transition by collision.

We investigate the impact of collisions with two-frequency photonic molecules aiming to observe internal dynamic behavior and challenge their strong robustness. Versatile interaction scenarios show intriguing state changes expressed through modifications of the resulting state such as temporal compression and unknown collision-induced spectral tunneling. These processes show potential for efficient coherent supercontinuum generation and all-optical manipulation.

Two-color pulse compounds in waveguides with a zero-nonlinearity point.

We study incoherently coupled two-frequency pulse compounds in waveguides with single zero-dispersion and zero-nonlinearity points. In such waveguides, supported by a negative nonlinearity, soliton dynamics can be obtained even in domains of normal dispersion. We demonstrate trapping of weak pulses by solitary-wave wells, forming nonlinear-photonics meta-atoms, and molecule-like bound-states of pulses.

Incoherent two-color pulse compounds: publisher's note.

This publisher's note contains corrections to Opt. Lett.46, 5603 (2021)OPLEDP0146-959210.

Incoherent two-color pulse compounds.

We study the dynamical evolution of two-frequency pulse compounds, i.e., intriguing bound-states of light, kept together due to their incoherent interaction.

Role of frequency dependence of the nonlinearity on a soliton's evolution in photonic crystal fibers.

We reveal the crucial role played by the frequency dependence of the nonlinear parameter on the evolution of femtosecond solitons inside photonic crystal fibers (PCFs). We show that the conventional approach based on the self-steepening effect is not appropriate when such fibers have two zero-dispersion wavelengths, and several higher-order nonlinear terms must be included for realistic modeling of the nonlinear phenomena in PCFs. These terms affect not only the Raman-induced wavelength shift of a soliton but also impact its shedding of dispersive radiation.

Crossover from two-frequency pulse compounds to escaping solitons.

The nonlinear interaction of copropagating optical solitons enables a large variety of intriguing bound-states of light. We here investigate the interaction dynamics of two initially superimposed fundamental solitons at distinctly different frequencies. Both pulses are located in distinct domains of anomalous dispersion, separated by an interjacent domain of normal dispersion, so that group velocity matching can be achieved despite a vast frequency gap.

Multi-frequency radiation of dissipative solitons in optical fiber cavities.

New resonant emission of dispersive waves by oscillating solitary structures in optical fiber cavities is considered analytically and numerically. The pulse propagation is described in the framework of the Lugiato-Lefever equation when a Hopf-bifurcation can result in the formation of oscillating dissipative solitons. The resonance condition for the radiation of the dissipative oscillating solitons is derived and it is demonstrated that the predicted resonances match the spectral lines observed in numerical simulations perfectly.

Dynamics of localized dissipative structures in a generalized Lugiato-Lefever model with negative quartic group-velocity dispersion.

We study localized dissipative structures in a generalized Lugiato-Lefever equation, exhibiting normal group-velocity dispersion and anomalous quartic group-velocity dispersion. In the conservative system, this parameter-regime has proven to enable generalized dispersion Kerr solitons. Here, we demonstrate via numerical simulations that our dissipative system also exhibits equivalent localized states, including special molecule-like two-color bound states recently reported.

Soliton Molecules with Two Frequencies.

We demonstrate a peculiar mechanism for the formation of bound states of light pulses of substantially different optical frequencies, in which pulses are strongly bound across a vast frequency gap. This is enabled by a propagation constant with two separate regions of anomalous dispersion. The resulting soliton compound exhibits moleculelike binding energy, vibration, and radiation and can be understood as a mutual trapping providing a striking analogy to quantum mechanics.

Experimental and theoretical study of the formation process of photopolymer based self-written waveguides.

The realization of optical interconnects between multimode (MM) optical fibers and waveguides based on a self-writing process in photopolymer media represents an efficient approach for fast and easy-to-implement connection of light-guiding elements. When light propagates through photopolymer media, it modulates the material properties of the media and confines the spreading of the light beam to create a waveguide along the beam propagation direction. This self-writing process can be realized with a single photopolymer medium and is also suited to connect optical fibers or waveguides with active elements such as light sources and detectors.

Single Transparent Piezoelectric Detector for Optoacoustic Sensing-Design and Signal Processing.

In this article, we present a simple and intuitive approach to create a handheld optoacoustic setup for near field measurements. A single piezoelectric transducer glued in between two sheets of polymethyl methacrylate (PMMA) facilitates nearfield depth profiling of layered media. The detector electrodes are made of indium tin oxide (ITO) which is both electrically conducting as well as optically transparent, enabling an on-axis illumination through the detector.

From Spin Glasses to Negative-Weight Percolation.

Spin glasses are prototypical random systems modelling magnetic alloys. One important way to investigate spin glass models is to study domain walls. For two dimensions, this can be algorithmically understood as the calculation of a shortest path, which allows for negative distances or weights.

Optoacoustic inversion via convolution kernel reconstruction in the paraxial approximation and beyond.

In this article we address the numeric inversion of optoacoustic signals to initial stress profiles. Therefore we study a Volterra integral equation of the second kind that describes the shape transformation of propagating stress waves in the paraxial approximation of the underlying wave-equation. Expanding the optoacoustic convolution kernel in terms of a Fourier-series, a best fit to a pair of observed near-field and far-field signals allows to obtain a sequence of expansion coefficients that describe a given "apparative" setup.

Effective one-dimensional approach to the source reconstruction problem of three-dimensional inverse optoacoustics.

The direct problem of optoacoustic signal generation in biological media consists of solving an inhomogeneous three-dimensional (3D) wave equation for an initial acoustic stress profile. In contrast, the more defiant inverse problem requires the reconstruction of the initial stress profile from a proper set of observed signals. In this article, we consider an effectively 1D approach, based on the assumption of a Gaussian transverse irradiation source profile and plane acoustic waves, in which the effects of acoustic diffraction are described in terms of a linear integral equation.

Fragmentation properties of two-dimensional proximity graphs considering random failures and targeted attacks.

The pivotal quality of proximity graphs is connectivity, i.e., all nodes in the graph are connected to one another either directly or via intermediate nodes.

Detection, numerical simulation and approximate inversion of optoacoustic signals generated in multi-layered PVA hydrogel based tissue phantoms.

Optoacoustic (OA) measurements can not only be used for imaging purposes but as a more general tool to "sense" physical characteristics of biological tissue, such as geometric features and intrinsic optical properties. In order to pave the way for a systematic model-guided analysis of complex objects we devised numerical simulations in accordance with the experimental measurements. We validate our computational approach with experimental results observed for layered polyvinyl alcohol hydrogel samples, using melanin as the absorbing agent.

Site- and bond-percolation thresholds in K_{n,n}-based lattices: Vulnerability of quantum annealers to random qubit and coupler failures on chimera topologies.

We estimate the critical thresholds of bond and site percolation on nonplanar, effectively two-dimensional graphs with chimeralike topology. The building blocks of these graphs are complete and symmetric bipartite subgraphs of size 2n, referred to as K_{n,n} graphs. For the numerical simulations we use an efficient union-find-based algorithm and employ a finite-size scaling analysis to obtain the critical properties for both bond and site percolation.

Analysis of the phase transition in the two-dimensional Ising ferromagnet using a Lempel-Ziv string-parsing scheme and black-box data-compression utilities.

In this work we consider information-theoretic observables to analyze short symbolic sequences, comprising time series that represent the orientation of a single spin in a two-dimensional (2D) Ising ferromagnet on a square lattice of size L(2)=128(2) for different system temperatures T. The latter were chosen from an interval enclosing the critical point T(c) of the model. At small temperatures the sequences are thus very regular; at high temperatures they are maximally random.

Biased and greedy random walks on two-dimensional lattices with quenched randomness: the greedy ant within a disordered environment.

The main characteristics of biased greedy random walks (BGRWs) on two-dimensional lattices with real-valued quenched disorder on the lattice edges are studied. Here the disorder allows for negative edge weights. In previous studies, considering the negative-weight percolation (NWP) problem, this was shown to change the universality class of the existing, static percolation transition.

Percolation thresholds on planar Euclidean relative-neighborhood graphs.

In the present article, statistical properties regarding the topology and standard percolation on relative neighborhood graphs (RNGs) for planar sets of points, considering the Euclidean metric, are put under scrutiny. RNGs belong to the family of "proximity graphs"; i.e.

Universality class of the two-dimensional randomly distributed growing-cluster percolation model.

We consider the "Touch and Stop" cluster growth percolation (CGP) model on the two-dimensional square lattice. A key parameter in the model is the fraction p of occupied "seed" sites that act as nucleation centers from which a particular cluster growth procedure is started. Here, we consider two growth styles: rhombic and disk-shaped cluster growth.

Information-theoretic approach to ground-state phase transitions for two- and three-dimensional frustrated spin systems.

The information-theoretic observables entropy (a measure of disorder), excess entropy (a measure of complexity), and multi-information are used to analyze ground-state spin configurations for disordered and frustrated model systems in two and three dimensions. For both model systems, ground-state spin configurations can be obtained in polynomial time via exact combinatorial optimization algorithms, which allowed us to study large systems with high numerical accuracy. Both model systems exhibit a continuous transition from an ordered to a disordered ground state as a model parameter is varied.

Analysis of the loop length distribution for the negative-weight percolation problem in dimensions d=2 through d=6.

We consider the negative weight percolation (NWP) problem on hypercubic lattice graphs with fully periodic boundary conditions in all relevant dimensions from d=2 to the upper critical dimension d=6. The problem exhibits edge weights drawn from disorder distributions that allow for weights of either sign. We are interested in the full ensemble of loops with negative weight, i.

Mean-field behavior of the negative-weight percolation model on random regular graphs.

We investigate both analytically and numerically the ensemble of minimum-weight loops in the negative-weight percolation model on random graphs with fixed connectivity and bimodal weight distribution. This allows us to study the mean-field behavior of this model. The analytical study is based on a conjectured equivalence with the problem of self-avoiding walks in a random medium.

Upper critical dimension of the negative-weight percolation problem.

By means of numerical simulations, we investigate the geometric properties of loops on hypercubic lattice graphs in dimensions d=2 through 7, where edge weights are drawn from a distribution that allows for positive and negative weights. We are interested in the appearance of system-spanning loops of total negative weight. The resulting negative-weight percolation (NWP) problem is fundamentally different from conventional percolation, as we have seen in previous studies of this model for the two-dimensional case.