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The ability to tailor the hopping interactions between the constituent elements of a physical system could enable the observation of unusual phenomena that are otherwise inaccessible in standard settings1,2. In this regard, a number of recent theoretical studies have indicated that an asymmetry in either the short- or long-range complex exchange constants can lead to counterintuitive effects, for example, the possibility of a Kramer’s degeneracy, even in the absence of spin 1/2 or the breakdown of the bulk–boundary correspondence3–8. Here we show how such tailored asymmetric interactions can be realized in photonic integrated platforms by exploiting non-Hermitian concepts, enabling a class of topological behaviours induced by optical gain. As a demonstration, we implement the Haldane model, a canonical lattice that relies on asymmetric long-range hopping to exhibit quantum Hall behaviour without a net external magnetic flux. The topological response observed in this lattice is a result of gain and vanishes in a passive but otherwise identical structure. Our findings not only enable the realization of a wide class of non-trivial phenomena associated with tailored interactions, but also open up avenues to study the role of gain and nonlinearity in topological systems in the presence of quantum noise. Non-Hermitian concepts together with optical gain allow the tailoring of short- and long-range exchange interactions in integrated topological photonics, and an exact Haldane model can be realized in this way.

We develop a rigorous theoretical framework based on principles from statistical mechanics that allows one to predict the equilibrium response of classical non-Hermitian arrangements in the weakly nonlinear regime. In this respect, we demonstrate that a pseudo-Hermitian configuration can always be driven into thermal equilibrium when a proper nonlinear operator is paired with the linear Hamiltonian of the system. We show that, in this case, the system will thermodynamically settle into an irregular pattern that does not resemble any known statistical distribution. Interestingly, this stable equilibrium response is associated with a Rayleigh-Jeans law when viewed within an appropriately transformed space that displays unitary dynamics. By considering a non-Hermitian Su-Schrieffer-Heeger chain, our results indicate that the thermodynamic equilibrium will always favor the edge modes instead of the ground state, in stark contrast to conventional nonlinear Hermitian configurations. Moreover, non-Hermitian lattices are shown to exhibit unusually high heat capacities, potentially acting as optical heat reservoirs to other Hermitian systems, by employing only a small number of sites and low power levels.

We study the propagation dynamics of bright optical vortex solitons in nematic liquid crystals with a nonlocal reorientational nonlinear response. We investigate the role of optical birefringence on the stability of these solitons. In agreement with recent experimental observations, we show that the birefringence-induced astigmatism can eventually destabilize these vortex solitons. However, for low and moderate birefringence, vortex solitons can propagate stably over experimentally relevant distances.

We theoretically investigate a Thouless pumping scheme in the 1D topological Su-Schrieffer-Heeger (SSH) model for single and multiple band-gaps systems when implemented in a discrete nematic liquid crystal arrangement. For an electrically controlled SSH waveguide array, we numerically demonstrate edge-to-edge light transport at low power levels. On the other hand, at higher powers, the transport is frustrated by light-induced nonlinear defect states, giving rise to robust all-optical switching., Accepted 23 December 2021 PRA

Most acousto-optic lenses produce energy dissipating annular fringes. Here, we report a 3D dynamic focusing with fully-localized focus and 477-fold beam confinement with an extended depth of field (DoF) of more than 28 cm.

We show that the orbital angular momentum (OAM) of a light field can be thermalized in a nonlinear cylindrical multimode optical waveguide. We find, that upon thermal equilibrium, the maximization of the optical entropy leads to a generalized Rayleigh-Jeans distribution that governs the power modal occupancies with respect to the discrete OAM charge numbers. This distribution is characterized by a temperature that is by nature different from that associated with the longitudinal electromagnetic momentum flow of the optical field. Counterintuitively and in contrast to previous results, we demonstrate that even under positive temperatures, the ground state of the fiber is not always the most populated in terms of power. Instead, because of OAM, the thermalization processes may favor higher order modes. A new equation of state is derived along with an extended Euler equation -- resulting from the extensivity of the entropy itself. By monitoring the nonlinear interaction between two multimoded optical wavefronts with opposite spins, we show that the exchange of angular momentum is dictated by the difference in OAM temperatures, in full accord with the second law of thermodynamics. The theoretical analysis presented here is corroborated by numerical simulations that take into account the complex nonlinear dynamics of hundreds of modes. Our results may pave the way towards high power optical sources with controllable orbital angular momenta, and at a more fundamental level, could shed light on the physics of other complex multimoded nonlinear bosonic systems that display additional conservation laws.

We theoretically investigate the effect of linear absorption on the stability of nonlinear vortex beams in dye-doped nematic liquid crystals. We show that the combined effects of intensity attenuation and thermal defocusing provide a stabilization mechanism which significantly extends the stable propagation distance of the vortex beam for first- and second-order topological charges.

We report the integration of quantitative-phase imaging (QPI) with light-sheet (LS) fluorescent microscopy on to a standard inverted microscope that retains compatibility with microfluidics. QPI enables label-free imaging and number-density quantification of single cells and their organelles. Conversely, LS yields considerable speed and phototoxicity gains in quantifying the 4D dynamics of gene-encoded fluorescent biomarkers. We will detail the system design that relied on spatial light interferometry for QPI and an accelerating Airy-beam light-sheet for fluorescence, its performance, as well as results of a representative multivariate imaging analysis of single-cell metabolism.

We report on the first observation of a gain-induced topological response in a photonic lattice exhibiting asymmetric long-range interactions enabled by unidirectional microrings under pumping. This new platform is used to implement the Haldane lattice.

We demonstrate that, due to nonlinear interactions, the orbital angular momentum in a multimode optical fiber can reach a thermal equilibrium state that is characterized by a temperature and a generalized Rayleigh-Jeans distribution.

We present a new scaling law that relates the thermodynamic pressure with the electrodynamic forces in multimode nonlinear dielectric waveguides. Our results are in exact agreement with those obtained using the Maxwell stress tensor formalism.

We study optical thermalization dynamics in integrated photonic coupled-cavity arrangements on a Si3N4 platform. We show that isolated photonic bandgap modes can reach positive or negative temperatures that can be predicted effortlessly using optical thermodynamics.

We investigate scalar and vector multi-hump spatial solitons resulting from competing Kerr-like nonlinear responses excited in a nonlocal medium by either one or two (mutually incoherent) light beams. Two-color vector supermode solitons are more amenable to control but exhibit an intriguing form of spontaneous symmetry breaking in propagation.

The complex nonlinear behaviors of heavily multimode lightwave structures have been recently the focus of considerable attention. Here we develop an optical thermodynamic approach capable of describing the thermalization dynamics in large scale nonlinear photonic chain networks - a problem that has remained unresolved so far. A Sackur-Tetrode equation is obtained that explicitly provides the entropy of these systems in terms of all the extensive variables involved. This entropic description leads to a self-consistent set of equations of state from where the optical temperature and chemical potential of the photon gas can be uniquely determined. Processes like isentropic expansion/compression, Joule expansion, as well as aspects associated with beam cleaning/cooling and thermal conduction effects in such chain networks are discussed. Our results open new vistas through which one can describe in an effortless manner the exceedingly complex dynamics of highly multimoded nonlinear bosonic systems that are nowadays of importance in areas ranging from high-power photonic settings to cold atom condensates and optomechanics.

Light-sheet microscopy enables considerable speed and phototoxicity gains, while quantitative-phase imaging confers label-free recognition of cells and organelles, and quantifies their number-density that, thermodynamically, is more representative of metabolism than size. Here, we report the fusion of these two imaging modalities onto a standard inverted microscope that retains compatibility with microfluidics and open-source software for image acquisition and processing. An accelerating Airy-beam light-sheet critically enabled imaging areas that were greater by more than one order of magnitude than a Gaussian beam illumination and matched exactly those of quantitative-phase imaging. Using this integrative imaging system, we performed a demonstrative multivariate investigation of live-cells in microfluidics that unmasked that cellular noise can affect the compartmental localization of metabolic reactions. We detail the design, assembly, and performance of the integrative imaging system, and discuss potential applications in biotechnology and evolutionary biology.

This Conference Presentation, Towards the experimental demonstration of topological Haldane lattice in microring laser arrays was recorded at Photonics West 2020 held in San Francisco, California, United States.

We report on the first demonstration of a topological Haldane lattice in a photonic setting using active microring structures.

We show that the optical brightness of a high-intensity multimode beam can be substantially enhanced using thermodynamic optical cooling schemes enabled by nonlinear interactions. This can be achieved without violating the second law of thermodynamics.

We show that a nonlinear topological Haldane lattice can exhibit a number of intriguing thermodynamic properties such as a metastable response leading to different temperatures in two bands or thermal equilibrium at different chemical potentials.

By utilizing notions from statistical mechanics, we develop a general and self-consistent theoretical framework capable of describing any weakly nonlinear optical multimode system involving conserved quantities. We derive the fundamental relations that govern the grand canonical ensemble through maximization of the Gibbs entropy at equilibrium. In this classical picture of statistical photo-mechanics, we obtain analytical expressions for the probability distribution, the grand partition function, and the relevant thermodynamic potentials. Our results universally apply to any other weakly nonlinear multimode bosonic system.

We report the first experimental observation of optical thermodynamic processes in nonlinear mesh photonic lattices. These include Rayleigh-Jeans distributions with either positive or negative temperatures, isentropic expansions and compressions, as well as Joule photon gas expansions.

Light-sheet fluorescence microscopy has greatly improved the speed and overall photostability of optically sectioning cellular and multi-cellular specimens. Similar gains have also been conferred by light-sheet Raman imaging; these schemes, however, rely on diffraction limited Gaussian beams that hinder the uniformity and size of the imaging field-of-view, and, as such, the resulting throughput rates. Here, we demonstrate that a digitally scanned Airy beam increases the Raman imaging throughput rates by more than an order of magnitude than conventional diffraction-limited beams. Overall, this, spectrometer-less, approach enabled 3D imaging of microparticles with high contrast and 1 µm axial resolution at 300 msec integration times per plane and orders of magnitude lower irradiation density than coherent Raman imaging schemes. We detail the apparatus and its performance, as well as its compatibility with fluorescence light-sheet and quantitative-phase imaging towards rapid and low phototoxicity multimodal imaging.

The collective response of a system is profoundly shaped by the interaction dynamics between its constituent elements. In physics, tailoring these interactions can enable the observation of unusual phenomena that are otherwise inaccessible in standard settings, ranging from the possibility of a Kramer's degeneracy even in the absence of spin to the breakdown of the bulkboundary correspondence. Here, we show how such tailored asymmetric coupling terms can be realized in photonic integrated platforms by exploiting non-Hermitian concepts. In this regard, we introduce a generalized photonic molecule composed of a pair of microring resonators with internal S-bends connected via two directional couplers and a link waveguide. By judiciously designing the parameters of this system, namely the length of the links and the power division ratio of the directional couplers, we experimentally show the emergence of Hermitian and non-Hermitian type exchange interactions. The ramifications of such coupling dynamics are then studied in 1D chain and ring-type active lattices. Our findings establish the proposed structure as a promising building block for the realization of a variety of phenomena, especially those associated with phase locking in laser arrays and non-Hermitian topological lattices.

We study experimentally the interaction of mutually incoherent bright spatial solitons in dye-doped nematic liquid crystals (LCs). The dye-induced light absorption results in a complex nonlinear optical response of the LC having spatially nonlocal focusing and defocusing contributions. The competition between both nonlinearities leads to the separation-dependent soliton interaction with repulsion of distant and attraction of closely placed solitons.

We show that the zeroth law of thermodynamics can be used to measure a soliton’s optical temperature in a nonlinear multimode system. Here, the modal gas plays the role of an optical thermometer.

Over the last few years, parity-time ($\mathcal{P}\mathcal{T}$) symmetry has been the focus of considerable attention. Ever since, pseudo-Hermitian notions have permeated a number of fields ranging from optics to atomic and topological physics, as well as optomechanics, to mention a few. Unlike their Hermitian counterparts, nonconservative systems do not exhibit a priori real eigenvalues and hence unitary evolution. However, once $\mathcal{P}\mathcal{T}$ symmetry is introduced, such dissipative systems can surprisingly display a real eigenspectrum, thus ensuring energy conservation during evolution. In optics, $\mathcal{P}\mathcal{T}$ symmetry can be readily established by incorporating, in a balanced way, regions having an equal amount of optical gain and loss. However, thus far, all optical realizations of such $\mathcal{P}\mathcal{T}$ symmetry have been restricted to a single transverse dimension (1D), such as arrays of optical waveguides or active coupled cavity arrangements. In most cases, only the loss function was modulated---a restrictive aspect that is only appropriate for linear systems. Here, we present an experimental platform for investigating the interplay between $\mathcal{P}\mathcal{T}$ symmetry and nonlinearity in two-dimensional (2D) environments, where nonlinear localization and soliton formation can be observed. In contrast to typical dissipative solitons, we demonstrate a one-parameter family of soliton solutions that are capable of displaying attributes similar to those encountered in nonlinear conservative arrangements. For high optical powers, this new family of $\mathcal{P}\mathcal{T}$ solitons tends to collapse on a discrete network---thus giving rise to an amplified, self-accelerating structure.

We report on the first experimental observation of stable vortex solitons in nematic liquid crystals with nonlocal nonlinear reorientational response. We show how these nonlinear vortex beams can be formed and confined in extraordinary optical waves by employing the cell with no lateral boundary conditions and the application of an external magnetic field that effectively controls the molecular direction and propagation of the self-trapped beams. We also find that these vortex solitons can be generated in certain ranges of the input beam power.

We study light propagation in nematic liquid crystals in the context of spatial optical solitons formation. We propose a simple analytical model with multiplicative nonlinearity, which represents (qualitatively) the liquid crystal response by comprising the competition between focusing (reorientational) and defocusing (thermal) nonlocal nonlinearities. We show that at sufficiently high input power the interplay between both nonlinearities leads to the formations of two-peak solitons, which represent supermodes of the self-induced extended waveguide structure. We explain the beam splitting mechanism, discuss threshold effects and conclude that similar phenomena might be present in other media with competing nonlocal nonlinearities.

We show that, in general, any complex weakly nonlinear highly multimode system can reach thermodynamic equilibrium that is characterized by a unique temperature and chemical potential. The conditions leading to either positive or negative temperatures are explicitly obtained in terms of the linear spectrum of the system, the input power, and the corresponding Hamiltonian invariant. Pertinent examples illustrating these results are provided in various scenarios.

We study numerically formation of spatial optical solitons in nematic liquid crystals with competing nonlocal nonlinearities. We demonstrate that at the sufficiently high input power the interplay between focusing and thermally induced defocusing may lead to the formation of two-peak fundamental spatial solitons. These solitons have constant spatial phase and hence represent supermodes of the self-induced extended waveguide structure. We show that these two-peak solitons are stable in propagation and exhibit adiabatic transition to a single peak state under weak absorption., Paper was submitted to Physical Review A

Simulation of light beam propagation in optical ber with a high step index requires the use of complicated methods. One of the simplest and accurate method is presented in this paper. The possibility of use of beam propagation method with exact boundary conditions in light beam propagation in optical bers is shown in this work. The comparison of this method with analytical solutions for planar waveguide and optical ber con rms usefulness of it.

In this paper a simple and effective method to analyze rectangular media with a high step of the refractive index is shown. Comparison of the method with a classical Beam Propagation Method and with analytical solutions for the planar waveguides in the (1+1)dimensional case are presented. There is also shown an influence of a high step of refractive index in (2+1)dimensional structures on the field distribution of guided beams as well as on the far field diffraction. The presented results show that the proposed method is very exact and relatively fast in comparison with other methods.

We investigate a non-homogeneous layered structure encompassing dual spatial dispersion: continuous diffraction in one transverse dimension and discrete diffraction in the orthogonal one. Such dual diffraction can be balanced out by one and the same nonlinear response, giving rise to light self-confinement into astigmatic spatial solitons: self-focusing can compensate for the spreading of a bell-shaped beam, leading to quasi-2D solitary wavepackets which result from 1D transverse self-localization combined with a discrete soliton. We demonstrate such intensity-dependent beam trapping in chiral soft matter, exhibiting one-dimensional discrete diffraction along the helical axis and one-dimensional continuous diffraction in the orthogonal plane. In nematic liquid crystals with suitable birefringence and chiral arrangement, the reorientational nonlinearity is shown to support bell-shaped solitary waves with simple astigmatism dependent on the medium birefringence as well as on the dual diffraction of the input wavepacket. The observations are in agreement with a nonlinear nonlocal model for the all-optical response.

In this work, we investigate a thin-film polarizer for a high intensity of the electromagnetic (EM) beam based on Cr nano wire arrays. Commonly used thin-film polarizing components are very sensitive for high power of EM waves and can be easily damaged by focused beams. The solution to this problem could be the thin-film polarizer based on metallic subwavelengths structures. This type of optical element has huge resistance comparing to typical thin-film polarizers. However, designing such an optical element for proper wavelength of EM wave and transmissions is not easy task. In this paper we present numerical as well as experimental results for specially designed chromium thin-film polarizer for wavelength 532nm Full Text: PDF References W. Zhou, K. Li, C. Song, P. Hao, M. Chi, M. Yu and Y. Wu, "Polarization-independent and omnidirectional nearly perfect absorber with ultra-thin 2D subwavelength metal grating in the visible region", Opt. Express 23, 11 (2015). CrossRef W. L. Barnes, A . Dereux, and T. W. Ebbesen, "Surface plasmon subwavelength optics", Nature 424, 824-830 (2003). CrossRef C. Lee, E. Sim, D. Kim, "Blazed wire-grid polarizer for plasmon-enhanced polarization extinction: design and analysis", Opt. Express 25, 7 (2017). CrossRef A. Lehmuskero, Metallic thin film structures and polarization shaping gratings (University of Eastern Finland 2010). Y. Leroux, J. C. Lacroix, C. Fave, V. Stockhausen, N. Felidj, J. Grandm, A. Hohenau, J. R. Krenn, "Active plasmonic devices with anisotropic optical response: a step toward active polarizer", Nano Lett. 5, 9 (2009). CrossRef R. T. Perkins, D. P. Hansen, E. W. Gardner, J. M. Thorne, A. A. Robbins, Broadband wire grid polarizer for the visible spectrum, US 6122103 (2000). DirectLink D. M. Sullivan, Electromagnetic simulation using the FDTD method, New York: IEEE Press Series (2000). CrossRef J. P. Berenger, Perfectly Matched Layer (PML) for Computational Electromagnetics, Morgan & Claypool Publishers (2007). CrossRef Yu, W., and R. Mittra, "A conformal FDTD software package modeling antennas and microstrip circuit components", IEEE Antennas Propagat. Magazine 42, 28 (2000) . CrossRef L. W. Bos, D. W. Lynch, "Optical Properties of Antiferromagnetic Chromium and Dilute Cr-Mn and Cr-Re Alloys", Phys. Rev. Sect. B, 2, 4267 (1970). CrossRef

We demonstrate the evolution of higher order one-dimensional guided modes into two-dimensional solitary waves in a reorientational medium. The observations, carried out at two different wavelengths in chiral nematic liquid crystals, are in good agreement with a simple nonlocal nonlinear model.

In this paper theoretical and experimental results regarding discrete light propagation in photonic liquid crystal fibres (PLCFs) are presented. Particular interest is focused on tunability of the beam guidance obtained due to the variation in either external temperature or optical power (with assumption of thermal nonlinearity taking place in liquid crystals). Highly tunable (discrete) diffraction and thermal self-(de)focusing are studied and tested in experimental conditions. Specifically, spatial light localization and/or delocalization due to the change in tuning parameters are demonstrated, with possibility of discrete spatial (gap) soliton propagation in particular conditions. Results of numerical simulations (performed for the Gaussian beams of different widths and wavelengths) have been compared to those from experimental tests performed in the PLCFs of interest. Owning to the limit of experimental means, direct qualitative comparison was not quite accessible. Nevertheless, a qualitative agreement between theoretical and experimental data (obtained in analogous conditions) has been achieved, suggesting a compact and widely-accessible platform for the study of tunable linear (and nonlinear) discrete light propagation in two-dimensional systems. Proposed photonic structures are of a great potential for all-optical beam shaping and switching.

In this paper, the results of theoretical analyses and experimental tests related to the light propagation in the photonic crystal fiber (PCF) infiltrated with liquid crystal (LC) are presented. While refractive index of the inclusion is higher than that of silica glass, analyzed photonic structure can be considered as a matrix of mutually parallel waveguide channels. This connotes discrete light propagation to be observed in the photonic liquid crystal fiber (PLCF), with the output beam profile strongly dependent on geometrical and optical properties of both the beam and the fiber. Moreover, when the optical nonlinearity is taken into account, spatial light localization and/or delocalization can be obtained with the final scenario implied by the amount of optical power and the molecular orientation of LC. In special cases discrete spatial soliton can be obtained, paving thus the way for all-optical switching to be developed n PLCFs.