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Sub-wavelength chiral resonators formed from artificial structures exhibit exceedingly large chiroptical responses compared to those observed in natural media. Owing to resonant excitation, chiral near fields can be significantly enhanced for these resonators, holding great promise for developing enantioselective photonic components such as biochemical sensors based on circular dichroism (CD) and spin-dependent nonlinear imaging. In the present work, strong linear and nonlinear chiroptical responses (scattering CD > 0.15 and nonlinear differential CDs > 0.4) at visible and near infrared frequencies are reported for the first time for individual micrometer-scale plasmonic and dielectric helical structures. By leveraging dark-field spectroscopy and nonlinear optical microscopy, the circular-polarization-selective scattering behavior and nonlinear optical responses (e.g., second harmonic generation and two-photon photoluminescence) of 3D printed micro-helices with feature sizes comparable to the wavelength (total length is ∼5λ) are demonstrated. These micro-helices provide potential for readily accessible photonic platforms, facilitating an enantiomeric analysis of chiral materials. One such example is the opportunity to explore ultracompact photonic devices based on single, complex meta-atoms enabled by state-of-the-art 3D fabrication techniques. [ABSTRACT FROM AUTHOR]

For emerging biomedical applications of hyperpolarized xenon, the ability to obtain reliably high nuclear spin polarization levels is paramount. Yet, experimental nuclear spin polarization levels of xenon are highly variable and, more than often than not, well below what theory predicts. Despite rigorous and well-studied theoretical models for hyperpolarization and continuous-flow spin-exchange optical pumping (SEOP), there remains a substantial discrepancy between the theoretical and experimental polarization of 129 Xe; inexplicably, seemingly similar experimental parameters can yield very different polarization values. In this paper, the validity of the assumptions typically made about the thermodynamic state of the Rb vapor inside the optical pumping cell and the gas dynamics are investigated through finite element analysis simulations of realistic optical pumping cell models, while in situ optical and nuclear magnetic resonance spectroscopy measurements are used to validate the results of the simulations. Our results show that shorter xenon gas residence times and lower Rb vapor densities than those predicted by empirical saturated vapor pressure curves, along with incorrect SEOP parameters, are the primary cause of the discrepancy between theoretical and experimental polarization values reported in the literature. [ABSTRACT FROM AUTHOR]

Interest in layered organohalide perovskites is motivated by their potential for use in optoelectronic devices. In these systems, the smallest and largest quantum wells are primarily concentrated near the glass and air interfaces of a film, thereby establishing a gradient in the average values of the bandgaps. It has been suggested that this layered architecture promotes the funneling of electronic excitations through space in a manner similar to light-harvesting processes in photosynthetic antennae. Whereas energy and charge transfer are difficult to distinguish by conventional transient absorption techniques, it has recently been shown that these competing relaxation mechanisms may be separately targeted with nonlinear fluorescence (NLFL) and photocurrent "action spectroscopies." Here, we present perturbative rate functions to describe NLFL experiments conducted on layered perovskite systems. The formulas reproduce the patterns of resonances observed in experimental measurements and show how signatures of energy transfer manifest in two-dimensional spectra. Overall, this work suggests that NLFL spectroscopy may be used to fully reveal the trajectories of electronic excitations by correlating ultrafast energy transfer pathways to fluorescence emission from the thickest quantum wells. [ABSTRACT FROM AUTHOR]

Time- and angle-resolved photoemission spectroscopy is a powerful probe of electronic band structures out of equilibrium. Tuning time and energy resolution to suit a particular scientific question has become an increasingly important experimental consideration. Many instruments use cascaded frequency doubling in nonlinear crystals to generate the required ultraviolet probe pulses. We demonstrate how calculations clarify the relationship between laser bandwidth and nonlinear crystal thickness contributing to experimental resolutions and place intrinsic limits on the achievable time-bandwidth product. Experimentally, we tune time and energy resolution by varying the thickness of nonlinear β -BaB 2 O 4 crystals for frequency upconversion, providing a flexible experiment design. We achieve time resolutions of 58–103 fs and corresponding energy resolutions of 55–27 meV. We propose a method to select crystal thickness based on desired experimental resolutions. [ABSTRACT FROM AUTHOR]

First-principles modeling of nonlinear optical spectra in the condensed phase is highly challenging because both environment and vibronic interactions can play a large role in determining spectral shapes and excited state dynamics. Here, we compute two dimensional electronic spectroscopy (2DES) signals based on a cumulant expansion of the energy gap fluctuation operator, with specific focus on analyzing mode mixing effects introduced by the Duschinsky rotation and the role of the third order term in the cumulant expansion for both model and realistic condensed phase systems. We show that for a harmonic model system, the third order cumulant correction captures effects introduced by a mismatch in curvatures of ground and excited state potential energy surfaces, as well as effects of mode mixing. We also demonstrate that 2DES signals can be accurately reconstructed from purely classical correlation functions using quantum correction factors. We then compute nonlinear optical spectra for the Nile red and methylene blue chromophores in solution, assessing the third order cumulant contribution for realistic systems. We show that the third order cumulant correction is strongly dependent on the treatment of the solvent environment, revealing the interplay between environmental polarization and the electronic-vibrational coupling. [ABSTRACT FROM AUTHOR]

The simulation of multidimensional vibrational spectroscopy of condensed-phase systems including nuclear quantum effects is challenging since full quantum-mechanical calculations are still intractable for large systems comprising many degrees of freedom. Here, we apply the recently developed double Kubo transform (DKT) methodology in combination with ring-polymer molecular dynamics (RPMD) for evaluating multi-time correlation functions [K. A. Jung et al., J. Chem. Phys. 148, 244105 (2018)], providing a practical method for incorporating nuclear quantum effects in nonlinear spectroscopy of condensed-phase systems. We showcase the DKT approach in the simulation of the fifth-order two-dimensional (2D) Raman spectroscopy of Lennard-Jones liquids as a prototypical example, which involves nontrivial nonlinear spectroscopic observables of systems described by anharmonic potentials. Our results show that the DKT can faithfully reproduce the 2D Raman response of liquid xenon at high temperatures, where the system behaves classically. In contrast, liquid neon at low temperatures exhibits moderate but discernible nuclear quantum effects in the 2D Raman response compared to the responses obtained with classical molecular dynamics approaches. Thus, the DKT formalism in combination with RPMD simulations enables simulations of multidimensional optical spectroscopy of condensed-phase systems that partially account for nuclear quantum effects. [ABSTRACT FROM AUTHOR]

We illustrate a technique by which heterodyne-detected sum-frequency generation spectroscopy is performed at multiple angles of incidence in order to decompose components of the second-order susceptibility tensor when all beams are polarized parallel to the plane of incidence. As an illustration, we study the non-vibrationally resonant gold response. We benchmark our results by comparing with measurements obtained in a polarization scheme that isolates a single element of the susceptibility tensor. Our technique is particularly valuable in the case of metal substrates, where the surface selection rule often prevents spectra from being acquired in multiple beam polarizations. [ABSTRACT FROM AUTHOR]

Surfaces and interfaces play important roles in many processes and reactions and are therefore intensively studied, often with the aim of obtaining molecular-level information from just the interfacial layer. Generally, only the first few molecular layers next to the interface are relevant for the surface processes. In the past decades, 2nd-order nonlinear spectroscopies including sum-frequency generation and second harmonic generation have developed into powerful tools for obtaining molecularly specific insights into the interfacial region. These approaches have contributed substantially to our understanding of a wide range of physical phenomena. However, along with their wide-ranging applications, it has been realized that the implied surface-specificity of these approaches may not always be warranted. Specifically, the bulk quadrupole contribution beyond the electric dipole-approximation for a system with a weak nonlinear interface signal, as well as the diffuse layer contribution at charged interfaces, could mask the surface information. In this perspective paper, we discuss the surface-specificity of 2nd-order nonlinear spectroscopy, especially considering these two contributions. [ABSTRACT FROM AUTHOR]

It is challenging to grow atomically thin non-van der Waals perovskite due to the strong electronic coupling between adjacent layers. Here, we present a colloid-driven low supersaturation crystallization strategy to grow atomically thin Cs3Bi2Br9. The colloid solution drives low-concentration solute in a supersaturation state, contributing to initial heterogeneous nucleation. Simultaneously, the colloids provide a stable precursor source in the low-concentration solute. The surfactant is absorbed in specific crystal nucleation facet resulting in the anisotropic growth of planar dominance. Ionic perovskite Cs3Bi2Br9 is readily grown from monolayered to six-layered Cs3Bi2Br9 corresponding to thicknesses of 0.7, 1.6, 2.7, 3.6, 4.6 and 5.7 nm. The atomically thin Cs3Bi2Br9 presents layer-dependent nonlinear optical performance and stacking-induced second harmonic generation. This work provides a concept for growing atomically thin halide perovskite with non-van der Waal structures and demonstrates potential application for atomically thin single crystals' growth with strong electronic coupling between adjacent layers. It is challenging to grow atomically thin non-van der Waals perovskites due to strong electronic coupling between adjacent layers. Here authors present the growth of perovskite single crystal nanosheets using a low supersaturation crystallisation strategy. [ABSTRACT FROM AUTHOR]

We study theoretically the features of the spectra of high-order harmonics of laser radiation generated in an ensemble of aligned diatomic molecules outside the framework of the strong-field approximation. The studies were carried out on the basis of numerical calculations within the framework of a model given by a two-center generalization of the Yukawa potential. Influence of the interference of contributions from different electron trajectories and the ion core potential on the accuracy of extracting spectroscopic information about the state of the nuclear subsystem of a molecule using high temporal resolution nonlinear spectroscopy based on the analysis of multicenter effects in the spectra of high-order harmonics has been explored. [ABSTRACT FROM AUTHOR]

Solvent as a complex environment can surround solute molecules and modify their function. In this work, different solute–solvent interaction effects on the nonlinear optical behavior of some azo dyes were studied at the molecular level. In this case, spectroscopic technique and density functional theory were used. According to the results, molecular dipole transition, changes between ground and excited state dipole moments, substituent, and environment polarity play considerable effects on the molecular nonlinear optical responses. In addition to solvent effects on the molecular first- and second-order hyperpolarizability, the two-photon absorption cross-section is also modified due to solvent-induced interactions. Moreover, the determination of the contribution of dominant solvent effects on the molecular nonlinear optical behavior can facilitate the studies on the application of optical samples in designing various optical systems. [ABSTRACT FROM AUTHOR]

Context: Fullerenes are of high significance due to their unique chemical properties and various applications in technology, particularly materials science, drug delivery, electronics, and nanoelectronics. In the recent years, many attempts have been focused to introduce new heteroatom-doped fullerenes having advanced chemical properties and tunable electronic traits, which make them a potential candidate for application in many branches of sciences. In this study, a novel C50N10 azafullerene with a fascinating structure of chained nitrogen atoms on a buckyball pole, with different electronic and optical properties compared to its other analogs, is introduced and trace of N–N substructures on the surface of C60 fullerene cage is investigated. For this molecule, four structural isomers including 3 structures with chain N atoms on a fullerene buckyball pole (NP isomers) and one isomer with separated N atoms (SN isomer) have been studied. All isomers have been studied with and without symmetry constraints, and the symmetry influence on the structure and stability of each isomer has been investigated. Although the studied NP structures have lower stability than the SN isomer, some reasons (such as their more all-carbon hexagonal rings, breaking some of their N–N bonds for partial opening of the cage and creating bigger rings in order to get rid of the unfavorable strain, as well as decreasing the N–N lone pair repulsions) lead to the acceptable stability of these structures with the bonded N atoms. The results of atomization energy and vibrational frequency calculations indicate that isomers with the bonded N atoms have acceptable stabilities and do not decompose into their constituent components. Investigation on the structural parameters demonstrates important roles of the number of all-carbon hexagonal rings, the number of N–N junction, and the molecule symmetry in the stability of the structures with the bonded N atoms. Study on the electronic and optical properties indicates that the target structures exhibit high electronic polarizability, relatively small HOMO/LUMO gap, high first- and second-order hyperpolarizability, and also large third-order nonlinear optical properties. Methods: All calculations have been performed using Gaussian G09 software using density functional theory (DFT) approach. Three-parameter Beck hybrid exchange functional (B3) hybridized with nonlocal correlation functional of Lee, Yang, and Parr (LYP) has been employed as the level of DFT calculations. All optimizations have been performed at double-zeta polarized (DZP) split valence 6-31G(d,p) and also at split valence TZP 6-311G(d,p) basis sets. The global minimum structures have been confirmed by frequency calculations at the same level of optimizations. The natural bond orbital (NBO) analyses, frontier orbital surfaces imaging, atomic charges, and charge transfer analyses have been achieved by GenNBO program package. [ABSTRACT FROM AUTHOR]

We explore the critical and scaling behavior of delayed bifurcations in systems with dynamic disorder well-known in kinetics when the control parameter in the rate is made to sweep stochastically across the critical point. The analysis is based on an extended Hamiltonian system that includes noise as an additional degree of freedom conjugate to the relevant dynamical variable. Appropriate quantifiers for measuring the time delay in reaching the bifurcation point have been introduced. We show that the time delay (i.e., the time difference between the static and dynamic bifurcation times) exhibits a power law decay with the deviation of the control parameter from its critical value, the decay constant being close to unity and is independent of the nature of bifurcations. The characteristic time to reach the zero solution state decreases algebraically with the deviation of the dynamical variable from its critical value and the decay exponent scales as the highest power of nonlinearity characterizing the nature of bifurcations. Bifurcations are essential features of various chemical kinetics; biological and ecological evolution. Critical and scaling behavior of delayed bifurcations in such systems with dynamic disorder has been explored when the control parameter in the rate is varied stochastically across the critical point. [ABSTRACT FROM AUTHOR]

We investigated the antipodal-symmetric dispersion maps of a dispersion-managed link with a midway optical phase conjugator to compensate for the distorted 960 Gb/s wavelength division multiplexed (WDM) signal caused by these effects. The proposed antipodal-symmetric dispersion map has various shapes depending on the detailed design scheme. We confirmed that the dispersion-managed link designed with the dispersion map of the antipodal-symmetric structure is more advantageous than the conventional uniform dispersion map for compensating WDM channels. It was also confirmed that among the antipodal-symmetric structures, the dispersion map configured with the S-1-profile, in which S is inverted up and down, was more effective for distortion compensation than the dispersion map configured with the S-profile. In particular, we confirmed that the S-1-profile can broaden the optical pulse width intensively at a short transmission distance, more effectively compensating for the distorted WDM channel. Because this structure makes the intensity of the optical pulse relatively weak, it can decrease the nonlinear Kerr effect. [ABSTRACT FROM AUTHOR]

Fully π‐conjugated ladder polymers with a spiral geometry represent a new class of helical polymers with great potential for organic nanodevices, but there is no precedent for an optically active helical ladder polymer totally composed of achiral units. We now report the defect‐free synthesis and resolution of a fully π‐conjugated helical ladder polymer with a rigid helical cavity, which has been achieved by quantitative and chemoselective acid‐promoted alkyne benzannulations of a rationally designed, random‐coil achiral polymer followed by chromatographic enantioseparation. Because of a sufficiently high helix‐inversion barrier, the isolated excess one‐handed helical ladder polymer with a degree of polymerization of more than 15 showed a strong circular dichroism with a dissymmetry factor of up to 1.7×10−2 and is thermally stable, maintaining its optical activity in solution even at 100 °C, as well‐supported by molecular dynamics simulation. [ABSTRACT FROM AUTHOR]

We have investigated the preparation and nonlinear optical characterization of Ge20Te75Bi5 (GTB) nano colloidal solutions using the z-scan technique for three different concentrations. The transmission spectra of GTB nano colloid films have been investigated. FTIR spectra have been measured to confirm the presence of amines in nano colloidal solutions. Z-scan traces at 78 × 1012 W/cm2 laser intensity were used to study the nonlinearity of the samples. The nonlinear absorption coefficient increases with an increase in the concentration of nano colloids. The reported high nonlinear response is useful for optical limiting applications. The optical limiting behavior is also studied against different concentrations. [ABSTRACT FROM AUTHOR]

The crystal of potassium dichromate-doped l-alanine (LAKDC), a nonlinear optical material, was made from an aqueous solution using a slow evaporation process with excellent transparency. The crystal's lattice parameters of the grown single crystal's orthorhombic structure of P212121 with lattice parameter values are a = 6.074 Å, b = 12.390 Å and c = 5.809 Å. FTIR analysis was used to ascertain qualitatively the presence of pure and dopant functional groups. Transmission and absorption spectra in the wavelength range of 200–800 nm were used to measure the crystal's optical and electronic properties in the UV–Vis–NIR range. The bandgap of the LAKDC crystal was noticed to be 4.81 eV. Differential thermal analysis and thermogravimetric analysis were used to investigate the crystal's thermal stability. The samples had better relative NLO efficiency and emitted a quantity of green light. The continuous-wave Nd:YAG laser was used to perform single beam z-scan tests of third-order nonlinearity. Open and closed aperture z-scan experiments demonstrate that the crystals exhibit negative nonlinearity and saturation absorption, respectively. [ABSTRACT FROM AUTHOR]

In this research, Zn(1−x)CrxAl2O4 (x = 0.00, 0.05, 0.10, 0.20) nanoparticles were prepared by a simple and green chemistry synthesis using gelatin as a polymerization agent. X-ray diffraction technique and scanning electron microscopy imaging were used to analyze the structural and morphological properties of the samples. X-ray diffraction results revealed that all samples were polycrystalline and crystallized in a cubical spinel phase. With increasing the x from 0.00 to 0.20, the main Bragg peaks shift to smaller angles, and the crystallite size and energy bandgap of samples decrease as well. The nonlinear absorption coefficient, β, and nonlinear refractive index, n2, of Zn(1−x)CrxAl2O4 were meticulously studied by the Z-scan approach. The orders of n2 and β are 10−7 and 10−4 cm/W, respectively. The saturable absorption and the self-defocusing effect are the main factors in the appearance of β and n2, respectively. The experimental results confirmed that increasing the percentage of Cr caused nonlinear coefficients to increase. [ABSTRACT FROM AUTHOR]

Novel materials of (E)-N'-(4-chlorobenzylidene)-4-hydroxybenzohydrazide (CBHB) and (E)-N'-(4-(diethylamino) benzylidene)-4-hydroxybenzohydrazide (DEABHB) were synthesized by condensation reaction process and solvent evaporation method was employed to grow CBHB and DEABHB single crystals at room temperature. Lattice parameters of CBHB and DEABHB compounds were recorded using single crystal X-ray diffraction method. The presence of functional groups of the synthesized CBHB and DEABHB compounds were confirmed by Fourier transform infrared and Fourier transform Raman spectral analyses. Various intermolecular interactions were studied using Hirshfeld surface analysis. Thermal stability of the hydrazone Schiff base compounds CBHB and DEABHB were studied by thermogravimetric and differential thermal analyses. Third order nonlinear optical properties of CBHB and DEABHB were measured using open aperature Z scan technique. Two photon absorption coefficient and optical limiting properties of the crystals were reported from the Z scan studies. [ABSTRACT FROM AUTHOR]

The interface pressure between the cable attachment and the body is crucial for the stable long-term operation of the cable. To solve the issue of interface insulation characteristics' damage caused by the pressure transducer measurement method, a non-destructive testing method of silicone rubber interface pressure using nonlinear ultrasound is presented. Initially, the study analyzes the propagation characteristics of ultrasonic waves at the interface of cross-linked polyethylene and silicone rubber. The study also establishes the relationship between the nonlinear coefficient and the interface pressure. Subsequently, a nonlinear ultrasonic test platform is constructed using the pulse reflection method to measure the interface pressure of flat silicone rubber and cross-linked polyethylene through nonlinear ultrasonic testing. Theoretical and experimental results indicate that the fundamental amplitude of the frequency domain of the interface reflection wave decreases, and the second harmonic amplitude and nonlinear coefficient both increase as pressure increases. These results demonstrate that the nonlinear ultrasound, non-destructive testing method can accurately evaluate the interfacial pressure state of the cable accessories. [ABSTRACT FROM AUTHOR]

Optical metasurfaces have recently emerged as the game changer in light manipulation and opened up new perspectives in many subfields of optics and photonics. Recent developments in nonlocal metasurfaces, in which the nanoscale building blocks respond to the incoming light collectively rather than as individual objects, are especially promising for enhancing and controlling the nonlinear optical phenomena. In this article, we provide a brief overview of the basic principles of nonlocal metasurfaces in the context of their nonlinear optical functionalities. We discuss the origin and the regimes of the nonlocal response, covering the aspects of multiple scattering, radiation damping, quality factor, local-field enhancement, and temporal dynamics. Some important aspects are illustrated by computational examples. We also give our personal viewpoint on the selected ideas and research directions in nonlocal and nonlinear metasurfaces, including the role of spatial symmetry in nonlocal interactions, the effects of phase and momentum matching in frequency conversion, as well as the possibilities offered by new material platforms and novel concepts, such as bound states in the continuum, parity–time symmetry, and time-variant metasurfaces. [ABSTRACT FROM AUTHOR]

The article presents a study which developed a sum-frequency spectroscopic scheme with varying photon momenta as an all-optic solution for retrieving the vibrational spectra of the bonded water layer and the ion diffuse layer and, hence, microscopic structural and charging information about an interface. Topics include spectral decomposition by MD-SFVS experiment, charge neutrality of zwitterionic phosphatidylcholine (PC) lipid/water interfaces, and BIL structure of surfactant/water interfaces.

In this paper, a composed quantum system is investigated which can potentially be used to manipulate the state of a qubit through measurement-based feedback (MBF) control. The composed quantum system consists of a nonlinear single-sided Fabry-P´erot optomechanical cavity cascaded with a 2-level atom and it is driven by a coherent quantum field. Due to the presence of the quantum measurement, the state of the atom needs to be estimated based on the measurement results. The effect of the optomechanical cavity on the state of the 2-level atom is disclosed through a quantum filtering approach. To this end, the SLH framework is utilized to analyze and model the considered composed quantum system. Then, filtering equations of the composed quantum system are derived. Numerical simulations are done for different initial conditions as well as different input quantum fields. In addition, the effects of atom and cavity parameters are studied and the result shows that choosing appropriate values for these parameters can change the behavior of the system in the desired way. The filter simulation results are validated by demonstrating that the average of the estimations for 50 ensembles follows the result from the master equation. [ABSTRACT FROM AUTHOR]

Aurintricarboxylic (ATA) organic dye is a promising chemical compound candidate for several optical and electronic applications. However, this study aims to investigate the impact of molar concentrations and solvent type on the linear/nonlinear optical (NLO) properties of 5,5 ′ -[(3-carboxy-4-oxocyclohexa-2,5-dien-1-ylidene) methylene] bis (2-hydroxybenzoic acid) organic laser dyes. Three molar concentrations of organic dyes (2 × 1 0 − 3 , 4 × 1 0 − 3 , and 6 × 1 0 − 3 ) M were respectively dissolved in distilled water and dimethylsulfoxide (DMSO) at room temperature. The samples were investigated using 1H-NMR and UV/Visible spectrums. The bandgap ( E g ) of (2 × 1 0 − 3 M) ATA/water is 4.75 eV, but Eg of ATA/DMSO was 2.93 eV and 2.65 eV. The measurements were performed by employing a diode-pumped solid-state laser operating at a 457 nm wavelength and 112 mW of power. The Z -scan technique was applied to characterize open and close apertures, nonlinear refractive index (n), and nonlinear absorption coefficient (β). The obtained results predicted that both the n and β coefficients decreased with the reduction of molar concentrations. Additionally, DMSO exhibited better linear/NLO properties than water. The results revealed promising laser dye samples for image sensor and optical limiter applications. [ABSTRACT FROM AUTHOR]

In this work, PEO/NiO films composed of polyethylene oxide (PEO) and nickel oxide (NiO) were fabricated using solution cast method to be used in optoelectronics applications. The PEO/NiO films are irradiated by oxygen fluence of 0.8 × 1018, 1.6 × 1018, and 2.4 × 1018 ions/cm2. The XRD as well as FTIR techniques were used to assess the effect of ion bombardment on the crystalline structures and functional group of PEO/NiO films. The absorption (A) and reflection (R) of the untreated and irradiated films was determined using UV–vis spectrophotometer in wavelength range of 200 to 1000 nm at room temperature. The data of A and R were used to calculate the parameters including band gap (Eg), absorption coefficient (α) and refractive index (n). The band gap as well as Urbach energies of un-bombarded as well as bombarded PEO/NiO films was calculated by Tauc's relationship. The band gap is reduced from 3.37 eV for PEO/NiO, to 2.66 eV, 2.57 eV and 2.50 eV after exposed to 0.8 × 1018, 1.6 × 1018, and 2.4 × 1018 ions/cm2 correspondingly, Moreover, the ubrach band tail is increased from 1.25 eV for PEO/NiO to 1.36 eV,1.41 eV and 1.45 eV after oxygen irradiation respectively. Additionally, linear optical characteristics have been calculated, including the refractive index and dielectric constant. The dispersing factors of the investigated films have also been computed using the Wemple-Di-Domenico model. The non-linear optic susceptibilities and refractive indices are calculated for un-bombarded as well as bombarded films. This work concluded that the optical behaviour of the bombarded PEO/NiO composite films were modified, indicating that these composites films can used in optoelectronics devices. [ABSTRACT FROM AUTHOR]

We develop a nonlinear theory of propagation of a monochromatic light wave in a gas of two-level atoms under the condition of inhomogeneous Doppler lineshape broadening, while considering a self-consistent solution of the Maxwell–Bloch equations in the mean-field approximation using a single atom density matrix formalism. Our approach shows a significant deformation of the Doppler resonant lineshape (shift, asymmetry), which depends on the atomic density. These effects are a consequence of only the free motion of atoms in a gas and is not associated with interatomic interaction. In particular, the frequency shift of the field-linear contribution to the transmission signal is more than an order of magnitude greater than the shift due to the interatomic dipole–dipole interaction, and the first nonlinear correction has an even stronger deformation, which exceeds the effect of the interatomic interaction by three orders of magnitude. The found effects caused by the free motion of atoms require a significant revision of the existing picture of spectroscopic effects, which depend on the atomic density in a gas. [ABSTRACT FROM AUTHOR]

The Harrow, Hassidim, Lloyd (HHL) algorithm, known as the pioneering algorithm for solving linear equations in quantum computers, is expected to accelerate solving large-scale linear ordinary differential equations (ODEs). To efficiently combine classical and quantum computers for high-cost chemical problems, non-linear ODEs (e.g., chemical reactions) must be linearized to the highest possible accuracy. However, the linearization approach has not been fully established yet. In this study, Carleman linearization was examined to transform nonlinear first-order ODEs of chemical reactions into linear ODEs. Although this linearization theoretically requires the generation of an infinite matrix, the original nonlinear equations can be reconstructed. For the practical use, the linearized system should be truncated with finite size and the extent of the truncation determines analysis precision. Matrix should be sufficiently large so that the precision is satisfied because quantum computers can treat such huge matrix. Our method was applied to a one-variable nonlinear y ˙ = - y 2 system to investigate the effect of truncation orders and time step sizes on the computational error. Subsequently, two zero-dimensional homogeneous ignition problems for H2–air and CH4–air gas mixtures were solved. The results revealed that the proposed method could accurately reproduce reference data. Furthermore, an increase in the truncation order improved accuracy with large time-step sizes. Thus, our approach can provide accurate numerical simulations rapidly for complex combustion systems. [ABSTRACT FROM AUTHOR]

In the present work, we analyze the influence of the polarization effects taking place during the course of a 2DIR spectroscopy experiment performed on a molecular system undergoing an intermolecular vibrational energy transfer process. When both donor and acceptor molecules participating in the vibrational energy transfer are embedded in a host solvent, they face rotational diffusion that strongly distorts the resulting 2DIR spectra. It could be expected that the difference between rotational diffusion constants will be of particular interest. For this purpose, the polarization effects are discussed according to the different orderings of the laser‐molecule interactions. Next, we study the distortions of the spectra as a function of the rotational diffusion constants of the individual molecules. The knowledge of these polarization effects is relevant to the interpretation of the spectra. Finally, the conclusions reached in this work for a vibrational energy transfer are valid for any other type of third‐order optical process performed on the same molecular system. [ABSTRACT FROM AUTHOR]

We report the terahertz (THz)-based characterisation of a highly efficient non-linear optical compound (E)-2-(4-(dimethyl amino) styryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (P-BI) single crystal. The crystallographic structure of the grown crystal was confirmed by single-crystal X-ray diffraction analysis. Based on the obtained diffraction analysis, the title crystal belongs to the space group P21 and possesses good optical transmission between 700 and 1500 nm. The most important impedance spectroscopy-based parameters such as dielectric constant and dielectric losses show lower values which are an essential requirement for general non-linear optical (NLO) materials. The femtosecond oscillator has helped us to ascertain the transmission/absorption and generation in the 0.2–2.0 THz range. The obtained experimental data were used for the measurement of real and imaginary parts of the refractive index and absorption coefficients of the crystal. Finally, the crystal was subjected to the femtosecond laser amplifier for measuring the efficiency, maximum generated power and effect of vertical rotation of the crystal on THz radiation. The output power was measured using a pyroelectric detector and the generated maximum power was of the order of 1.9 µW at 150 mW incident pump power. The corresponding efficiency of the generated THz signal is of the order of 1.26 × 10–3%. [ABSTRACT FROM AUTHOR]

Integrated nonlinear photonics, combined nonlinear optics with state‐of‐the‐art photonic integration, play a crucial role in chip‐integrated technologies including optical frequency combs, molecular spectroscopy, and quantum optics. Optical materials with favorable properties are the foundation to promote integrated photonic devices with bandwidth, efficiency, and flexibility in high‐volume chip‐scale fabrication. In this work, a newly developed chalcogenide glass‐Ge25Sb10S65 (GeSbS) is presented for nonlinear photonic integration and for dissipative soliton microcomb generation. The GeSbS features wide transparency (0.5–10 µm), strong nonlinearity (1.3 × 10−18 m2 W−1), and low thermo‐refractive coefficient (3.1 × 10−5 K−1), and is complementary metal oxide semiconductor (CMOS)‐compatible in fabrication. In this platform, chip‐integrated optical microresonators with an average intrinsic quality (Q) factor of ≈1.97 × 106 are implemented, and lithographically controlled dispersion engineering is carried out. In particular, both a bright soliton‐based microcomb with bandwidth of 240 nm (≈1440–1680 nm) and a dark‐pulse comb with bandwidth of 80 nm (≈1510–1590 nm) are generated in a single microresonator in its separated fundamental polarized mode families.The ten‐milliwatt level of soliton microcomb operation power facilitates the monolithically integrated photonic circuits. The results provide a potential material platform for integrated nonlinear photonics for highly compact and high‐intensity nonlinear interactions in visible and infrared regions. [ABSTRACT FROM AUTHOR]

Stoichiometric single crystals of Pb5(Ge1–хSix)3O11 solid solutions (0 ≤ x ≤ 0.55) are obtained by slow cooling of 5PbO·3(1–y)GeO2·3ySiO2 melts. The chemical analysis confirms their cation and anion stoichiometry. The effect of their high-energy (10 MeV) electron irradiation with fluences from 0.1·1018 e/cm2 to 4.39·1018 e/cm2 on the structural, ferroelectric, and nonlinear optical characteristics of the crystals is studied for the first time. The dependence of crystals on concentrations and fluences is detected. According to the date of dielectric spectroscopy and second harmonic generation of laser radiation, the doping with Si causes a systematic shift of Tc to low temperatures, a decrease in the peak value of the dielectric permittivity, and a noticeable phase transition smearing with transforming to the zelaxor ferrollectric state of x = 0.35. According to the structural studies of initial and irradiared, Pb5(Ge1–xSix)3O11 crystals, they retain the structural perfectness without any signs of amorphization. Structural distortions of Pb5(Ge1–xSix)3O11 do not significantly depend on the fluence. [ABSTRACT FROM AUTHOR]

Tartrazine is one of the food dyes with π conjugated bond. The optical nonlinear properties of tartrazine in aqueous solution were investigated by Z-scan technique at the different input intensities of picosecond laser pulse. It was found that the tartrazine exhibits strong nonlinear optical behavior at the low input intensity. The experimental results show the nonlinear refractive indices reach the order of 10 − 1 1 esu and their TPA cross sections are up to several hundreds of GM in the experimental condition. The strong optical nonlinearity perhaps allows them to be widely applied in the photoelectric and biological field. [ABSTRACT FROM AUTHOR]

This work investigates the complex Ginzburg-Landau equation (CGLE) with parat)olic law in nonlinear optics, this form of nonlinearity may also be seen in fiber optics, It is referred to as the fifth-order susceptibility, which is predominantly present in a transparent glass with intense femtoxecond pulses at 620nml, The φ6-model expansion approach is used to find dark, singular, periodic, and combined optical soliton solutions to the model, The results presented in this study are intended to improve the CGLE's nonlinear dynamical characteristics, These solitons are significant resources in physics and telecommunications engineering, They led to several quick follow-up investigations, The hyperholic sine, for example, appears in the calculation of the Roche limit and gravitational potential of a cylinder, while the hyperbolic cotangent appears in the Langevin function for magnetic polarization, Some of the obtained solutions' 2-, 3-dimensional, and contour plots are shown. [ABSTRACT FROM AUTHOR]

Intense terahertz (THz) pulses facilitate the observation of various nonlinear optical effects and the manipulation of material properties. In this work, we report a convenient approach to produce strong broadband THz pulses with a center frequency tunable between 2 and 4 THz. A coherent THz light source with a pulse energy of 1.2 mJ can be generated from low-cost crystalline quartz using a tilted-pulse-front scheme. Thanks to the wide transparent spectral window and high damage threshold, our theoretical analysis and experiment show that the THz conversion efficiency in quartz reaches 0.05%, which is comparable with that in LiNbO3 at room temperature, while the output THz spectral range is much broader in the former. This work not only provides the light source that is urgently needed for nonlinear THz spectroscopy beyond 2 THz but also offers an alternative route in selecting nonlinear optical crystals for optical frequency conversion. [ABSTRACT FROM AUTHOR]

A series of novel phenomena such as optical nonlinear enhancement effect, transmission enhancement, orientation effect, high sensitivity to refractive index, negative refraction and dynamic regulation of low threshold can be generated by the control of surface plasmon (SP) with metal micro-nano structure and metal/material composite structure. The application of SP in nano-photonics, super-resolution imaging, energy, sensor detection, life science, and other fields shows an important prospect. Silver nanoparticles are one of the commonly used metal materials for SP because of their high sensitivity to refractive index change, convenient synthesis, and high controllable degree of shape and size. In this review, the basic concept, fabrication, and applications of silver-based surface plasmon sensors are summarized. [ABSTRACT FROM AUTHOR]

Nickel contacts based on gallium arsenide are of interest from the point of view of their application in optoelectronics. The aim of this work is to study the contact structures of Ni–p-GaAs and Ni–n-GaAs. The object of study is the electrochemical contacts of nickel to crystalline gallium arsenide. The article presents studies of the topography of homogeneous electrochemical nickel films of nanometer thickness (50–100 nm) on the surface of a semiconductor. The current–voltage characteristics of metal–semiconductor contacts are experimentally obtained. The roughness of the GaAs substrate of the Ni film was studied using optical and probe microscopes. Nickel films were obtained using a Watts solution and a setup for the production of electrochemical structures by the drop method. To minimize the roughness of the nickel surface obtained by electrolysis, a mode of low current density is used. Using a theoretical model and experimental data, the contact resistances are calculated and their current–voltage characteristics are obtained. The parameters of nickel surface roughness, which affect the operational properties of contact structures, are determined. The features of the current flow through the electrochemically obtained Ni–GaAs contacts are revealed. It is shown that the resulting Ni–p-GaAs structures are Ohmic, and the current–voltage characteristics of the Ni–n-GaAs contacts have a nonlinear region at voltages less than 1.5 V. It is shown that the formation of an integral nickel film on the GaAs surface is possible when the Ni layer thickness exceeds the average substrate roughness. [ABSTRACT FROM AUTHOR]

In the past twenty years, the basic investigation of innovative Non-Linear Optical (NLO) crystals has received significant attention, which has built the crucial heritage for the use of NLO materials. Fundamental research is essential given the scarcity of materials for NLO compounds, especially in the deep ultraviolet (DUV) and middle- and far-infrared (MFIR) regions. In the present work, we synthesized high-quality MFIR SbI3·3S8 NLO crystals having a length in the range of 1–5 mm through rapid facile liquid phase ultrasonic reaction followed by the assistance of instantaneous natural evaporation phenomenon of the solvent at room temperature. X-ray diffraction (XRD) results ratify the hexagonal R3m structure of SbI3·3S8 crystal, and energy-dispersive X-ray spectroscopy (EDX) demonstrates that the elemental composition of SbI3·3S8 crystal is similar to that of its theoretical composition. The direct and indirect forbidden energy gaps of SbI3·3S8 were measured from the optical transmittance spectra and they were shown to be 2.893 eV and 1.986 eV, respectively. The green sparkling signal has been observed from the crystal during the second harmonic generation (SHG) experiment. Therefore, as inorganic adducts are often explored as NLO crystals, this work on the MFIR SbI3·3S8 NLO crystal can bring about additional investigations on this hot topic in the near future. [ABSTRACT FROM AUTHOR]

In this paper, we present the temporal and spectral shaping of kilovolt picosecond electrical pulses obtained by using the linear switching process with femtosecond laser source. The frozen wave generator integrating up to four photoconductive semiconductor switches is activated by varying the optical pulse amplitude and time delay. Electric pulses with rise time and duration as short as 60 and 100 ps, respectively are used to implement a microwave spectroscopy experiment. This optoelectronic device is synchronous with the optical pulses which can be used for optical spectroscopy, after nonlinear frequency conversion. This single‐shot microwave spectroscopy technique was used to characterize the resonances of a passive dielectric resonator. Pulse shaping integrating coherent wave combining is also demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] The stability of emulsions requires the fast formation of viscoelastic interfaces between water and oil phases. In double emulsions, two surfactant types (hydrophilic and lipophilic) are present and two interfacial films are involved. Understanding cooperative adsorption of these surfactants and its implication on properties of water/oil/water interfacial films will enable replacing the empirical methodologies used in designing double emulsion systems with a knowledge-based approach. The distribution of surfactants between the water/oil interfaces was investigated using single droplet diffusion experiments and simulation of equilibrium surfactant density profiles. The stability of the interfaces against coalescence was characterized by dye transport in a leach cell and coalescence time of single droplets in a model experiment. The conformation of the surfactants at an interface was then examined via surface rheology, sum frequency generation spectroscopy, and dissipative particle dynamics simulation. Two selected hydrophilic surfactants combined with a lipophilic surfactant induce very different properties at water/oil interfaces and different dye release behaviour from their corresponding double emulsions. Competitive adsorption of sodium dodecyl sulfate and lipophilic surfactant results in the improvement of encapsulation efficiency, elasticity of the interface, and resistance against coalescence due to the intercalation of surfactant alkyl chains into the oil chains. [ABSTRACT FROM AUTHOR]

Thiourea manganese (II) sulfate (TM2S) is a nonlinear optical single crystal that has been successfully grown using a solvent evaporation technique. X-ray diffraction analysis of a single crystal confirms that TM2S formed in the orthorhombic system with the non-Centro symmetric Pnma space group. FTIR spectroscopy analysis revealed the presence of several functional groups in TM2S. The crystal optical characteristics were verified by measuring its UV-visible spectrum. The melting point was determined by differential scanning calorimetry, and the thermal sensitivity of the formed crystal was determined by thermo gravimetric analysis. At various temperatures, the dielectric property of the grown crystal was studied. Using the Kurtz-powder approach, the second harmonic generation in TM2S has been explored. Quantum chemical estimations, such as HOMO-LUMO, were calculated and reported. In order to quantify the surface laser damage of the crystal, a laser with multiple shots was used. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of composite liquid crystal (LC) cells containing gold nano-island film (AuNIF) deposited on one of the cell substrates are studied with the help of dynamic holographic techniques. A dynamic phase grating of a photoinduced change in the refractive index arises in a composite LC cell when the two-wave mixing of laser beams of a cw Nd:YAG laser is used. The nonlinear optical response is caused due to a surface-induced photorefractive effect observed under the simultaneous action of a periodic light interference pattern and a constant voltage. The result of this impact is appearance of an internal electric field (Eint) at the AuNIF-LC interface. This electric field defines the local reorientation of LC molecules. Our experimental studies prove that the Eint value can be controlled by the size and shape of Au nanoparticles in AuNIF. As a result, we obtained a record of either fast dynamic gratings or quasi-stationary gratings in the composite LC cells depending on the morphology of AuNIF. [ABSTRACT FROM AUTHOR]

Purpose: Currently, conjugated nonlinear optical (NLO) materials suffer from the drawbacks of complex manufacturing process and high cost. To further study the NLO materials with cost-effective, it is necessary to prepare new NLO materials with satisfactory performance. Design/methodology/approach: Pyrene derivatives with good third-order NLO properties were synthesized by combining pyrene compounds with TCNE, TCNQ, F4-TCNQ and other molecular systems by clicking chemical method. Findings: The pyrene derivatives were characterized by ultraviolet spectrum and Z-scan. The charge-transfer of the D-p-A structures plays a key role in the absorption peak shifts. And the third-order nonlinear absorption of the products revealed good third-order NLO susceptibilities. Research limitations/implications: The synthesis technology of pyrene derivatives is not mature enough and is in the preliminary exploration stage. So, the authors produced a relatively small number of samples and did not conduct a very comprehensive test. Practical implications: This novel pyrene derivative is suggestive and can promote the exploration and development of the third-order nonlinear materials. Originality/value: Four new pyrene derivatives were synthesized by selecting new molecular systems. Because of its good chemical properties and stable properties, it can be a reference for the development of third-order nonlinear materials in the future. [ABSTRACT FROM AUTHOR]

A thermal stability, vibrational spectroscopy, electric response, linear and nonlinear optical (NLO) properties and optical properties of pure PVP polymer for solar cell device are investigated. The optimized geometry of the structural unit and oligomer (10 structural unit) of PVP polymer are shown. Absorption peaks in IR and Raman spectra are analyzed. The net atomic charges of PVP, obtained by means of Mulliken population analysis are studied. The electrostatic potential with respect to the surface at constant electron density is portrayed. Optical absorbance A (λ) spectrum of pure PVP is illustrated. The absorption spectrum of PVP polymer is studied and optical gap of PVP is determined. The DOS spectrum and the distributions of the HOMO and LUMO orbitals are represented. Effect of light on current–voltage measurement is evidenced recording an open circuit voltage of 0.25 V and short circuit current of 3.9 µA at 150 W/cm2. [ABSTRACT FROM AUTHOR]

We outline a novel numerical method, called Ultrafast Ultrafast (UF2) spectroscopy, for calculating the nth-order wavepackets required for calculating n-wave mixing signals. The method is simple to implement, and we demonstrate that it is computationally more efficient than other methods in a wide range of use cases. The resulting spectra are identical to those calculated using the standard response function formalism but with increased efficiency. The computational speed-ups of UF2 come from (a) nonperturbative and costless propagation of the system time-evolution, (b) numerical propagation only at times when perturbative optical pulses are nonzero, and (c) use of the fast Fourier transform convolution algorithm for efficient numerical propagation. The simplicity of this formalism allows us to write a simple software package that is as easy to use and understand as the Feynman diagrams that organize the understanding of n-wave mixing processes. [ABSTRACT FROM AUTHOR]

In this paper, we have discussed the enhanced three-wave mixing (TWM) nonlinear optical processing in a three-level symmetry broken three-level quantum system. The quantum system interacts with three drivel laser fields out of which two are weak probes and generated signal beams and one of them is strong coupling light. We have shown that due to symmetry broken of quantum system the nonlinear sum frequency generation leads to TWM. By adjusting the different system parameters, the efficiency of TWM mechanism can be improved. Moreover, we have found when the strong coupling light becomes optical vortex light, the efficiency of TWM depends on the orbital angular momentum (OAM) light. Our proposed model may be having useful applications in nonlinear spectroscopy based on OAM. [ABSTRACT FROM AUTHOR]

Contemporary design of new organic non-linear optical (NLO) materials relies to a large extent on the understanding of molecular and electronic structure–property relationships revealed during the years by available computational approaches. The progress in theory—hand-in-hand with experiment—has enabled us to identify and analyze various physical aspects affecting the NLO responses, such as the environmental effects, molecular vibrations, frequency dispersion, and system dynamics. Although it is nowadays possible to reliably address these effects separately, the studies analyzing their mutual interplay are still very limited. Here, we employ density functional theory (DFT) methods in combination with an implicit solvent model to examine the solvent effects on the electronic and harmonic as well as anharmonic vibrational contributions to the static first hyperpolarizability of a series of push–pull α , ω -diphenylpolyene oligomers, which were experimentally shown to exhibit notable second-order NLO responses. We demonstrate that the magnitudes of both vibrational and electronic contributions being comparable in the gas phase significantly increase in solvents, and the enhancement can be, in some cases, as large as three- or even four-fold. The electrical and mechanical anharmonic contributions are not negligible but cancel each other out to a large extent. The computed dynamic solute NLO properties of the studied systems are shown to be in a fair agreement with those derived from experimentally measured electric-field-induced second-harmonic generation (EFISHG) signals. Our results substantiate the necessity to consider concomitantly both solvation and vibrational effects in modeling static NLO properties of solvated systems. [ABSTRACT FROM AUTHOR]

The development of atomically thin single crystal films is necessary to potential applications in the 2D semiconductor field, and it is significant to explore new physical properties in low-dimensional semiconductors. Since, zero-dimensional (0D) materials without natural layering are connected by strong chemical bonds, it is challengeable to break symmetry and grow 0D Cs3BiX6 (X = Br, Cl) single crystal thin films. Here, we report the successful growth of 0D Cs3BiX6 (X = Br, Cl) single crystal films using a solvent evaporation crystallization strategy. Their phases and structures are both well evaluated to confirm 0D Cs3BiX6 (X = Br, Cl) single crystal films. Remarkably, the chemical potential dependent morphology evolution phenomenon is observed. It gives rise to morphology changes of Cs3BiBr6 films from rhombus to hexagon as BiBr3 concentration increased. Additionally, the robust second harmonic generation signal is detected in the Cs3BiBr6 single crystal film, demonstrating the broken symmetry originated from decreased dimension or shape change. [ABSTRACT FROM AUTHOR]

The single crystal of hydroxyethylammonium D‐tartrate monohydrate (HEDT) is grown along the (1 1 0) plane using the Sankaranarayanan–Ramasamy method. The powder X‐ray diffraction and the high‐resolution X‐ray diffraction analyses are used to corroborate the growth plane and perfection of the crystallinity, respectively. The birefringence experiment has proven crystalline homogeneity and estimated birefringence value (Δn) is 0.109. The surface morphology of the grown crystal is examined by chemical etching analysis and irregular hillock patterns are found. The transmittance for the (1 1 0) plane of the HEDT is inspected by a UV‐Vis analysis. The second harmonic generation efficiency of the HEDT crystal is 1.7 times that of potassium dihydrogen phosphate (KDP). The third‐order nonlinear optical (TONLO) properties of the grown HEDT crystal are scrutinized by the Z‐scan experiment. The estimated TONLO susceptibility of HEDT crystal is 6.827 × 10−8 esu. The laser damage threshold value of HEDT is discovered to be 5.24 GW cm−2. The 3D Hirshfeld surface visualizes the interaction between HEDT molecules and analyzes the distance from the surface of the molecule to the farthest and the nearest atom. The important contributions of crystal packing are explored by 2D‐fingerprint plots. [ABSTRACT FROM AUTHOR]

Guanidinium hydrogen glutarate (GHG) was synthesized by slow evaporation method. X-ray diffraction (XRD) study reveals that GHG crystallized into a triclinic system with the space group P 1 ¯ . Crystallinity of the obtained GHG crystal was investigated with the help of the powder XRD analysis. High-intensity peak observed at 28° of the (1 –1 –2) plane confirms the good crystallinity of the GHG crystal. The crystalline nature of the synthesized crystal was tested through high-resolution XRD. The presence of different functional groups in the GHG material was analysed by the Fourier transform infrared and FT-Raman spectra. UV–Vis spectral analysis of the GHG material demonstrates 98% transmittance with a cut-off wavelength at 230 nm. The bandgap value of GHG is 5.01 eV. A peak at 421 nm is observed in the emission spectrum. The results imply that GHG crystals have a blue fluorescence emission. The thermal stability of the grown crystal was determined using thermal analysis. The GHG compound is stable up to 244°C and it has good degree of crystallinity. The mechanical behaviour of the title crystal was measured using microhardness studies. The GHG crystal shows that it belongs to soft material category. A dielectric study of the crystal was analysed at diverse temperatures. Third-order nonlinear optical (NLO) susceptibility is determined using through Z-scan studies. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third-order NLO susceptibility (χ(3)) were estimated to be –1.8545 × 10–8 (cm2 W–1), 3.8015 × 10–4 (cm W–1) and 2.2150 × 10–5 (esu), respectively. Optical limiting property of the GHG compound has also been discussed. [ABSTRACT FROM AUTHOR]