High Nonlinear Response Research Articles

Grid octet truss lattice materials for energy absorption

Octet truss lattice material, the most well-known stretching-dominated lattice material, is attracting attention in lightweight material engineering. Low resistance to buckling loading limits its use in lightweight energy absorbers. Here, we propose a new strategy to construct octet truss lattice materials with high mechanical properties and stable nonlinear compression response at low relative densities. The effective mechanical properties of the generated grid octet lattice materials have been investigated both numerically and experimentally. Results show that the relative elastic modulus, yield strength and specific energy absorption will increase with either the relative density or the number of the grid structure. At a relative density of 0.5 and compared to the truss lattice, the gain in Young’s modulus, yield strength, and SEA is 26%, 26% and 25%. Respectively. Additional compression test on the 316l stainless steel samples demonstrates introducing triangular grid structures suppresses the post-buckling behavior of the octet lattice. The generated grid octet lattice materials possess a nearly constant plateau stress between initial yield and densification, even at a relative density of about 0.2. The designed lattice material is thus a noteworthy alternative for load bearing and energy absorption.

The effect of human serum albumin on ZIF-8 used in drug delivery: structural, linear and nonlinear optical properties

Zeolitic Imidazolate Frameworks (ZIF-8) are extremely useful substances that have been utilized in a variety of commercial and medical applications due to their interesting properties. Understanding the properties of ZIF-8 doped human serum albumin with different concentrations can lead to the development of new applications in areas such as sensing, drug delivery, and catalysis. Here, we investigated the extent of interaction between ZIF-8 and HSA by examining the structural, linear, and nonlinear optical properties of ZIF-8@xHSA where x is 2.5, 5, 10 wt%. Scanning electron microscope and Transmission electron microscope images revealed that both ZIF-8 and ZIF-8@10 wt% HSA had regular cubic shapes, with average particle sizes of 38 nm and 49 nm, respectively. The X-ray diffraction shows a crystalline shape for ZIF-8 and ZIF-8@10 wt% HAS. The energy gap of our composite was calculated using the Wemple-Didomenico model, and it exhibited strong concentration-dependent behavior. The Z-scanner was used to investigate the nonlinear properties, which indicated that ZIF-8@10 wt%HSA had a high nonlinear response. As the understanding of this interaction deepens, it is expected that innovative applications in biomedical and pharmaceutical fields will emerge, highlighting the vital connection between HSA and ZIF-8.

Boron-rich triphenylene COF based electrides having excellent nonlinear optical activity

The desirability of the high nonlinear response of two-dimensional (2D) materials for electronics and optoelectronic devices drove us to investigate the nonlinear optical (NLO) behavior of alkali metal atom (AA) doped lithiated boron-containing hexahydroxy-triphenylene (LiBHHTP). In this context, the geometric, electronic, optical, and NLO properties are investigated. The doped AA atoms including Li, Na, and K preferably interact via the oxygen atoms of the LiBHHTP surface. The stability of the doped complexes is revealed by the interaction energies (Eint), which are −22.90, −16.10, and −16.52 kcal/mol for Li@LiBHHTP, Na@LiBHHTP, and K@LiBHHTP complexes, respectively. The alterations in the electronic behavior of LiBHHTP are observed upon doping with alkali atoms via Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), and the Density of State (DOS) analyses. The FMO analysis reveals that these complexes are electride in nature with absorption transparency in the UV–Vis range. Finally, the NLO behavior of designed complexes is evaluated through static and dynamic hyperpolarizabilities. Among reported complexes, K@LiBHHTP exhibits significantly large static hyperpolarizability (βₒ), 2.24 × 105 au. The dynamic NLO response of doped LiBHHTP complexes is also high, where the values are ranged in between 3.67 × 105 and 6.04 × 108 au at 1064 nm. This article not only highlights the effects of alkali atom doping on the NLO behavior of materials but also presents the first Lithiated boron-containing triphenylene as a next-generation optoelectronic material.

Concentration-dependent enhancement of nonlinear optical properties in Ge-Te-Bi nano colloidal solutions

ABSTRACT 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.

Toward Intrinsic Force Sensing and Control in Parallel Soft Robots

With soft robotics being increasingly employed in settings demanding high and controlled contact forces, recent research has demonstrated the use of soft robots to estimate or intrinsically sense forces without requiring external sensing mechanisms. While this has mainly been shown in tendon-based continuum manipulators or deformable robots comprising of push–pull rod actuation, fluid drives still pose great challenges due to high actuation variability and nonlinear mechanical system responses. In this work, we investigate the capabilities of a hydraulic, parallel soft robot to intrinsically sense and subsequently control contact forces. A comprehensive algorithm is derived for static, quasi-static, and dynamic force sensing, which relies on fluid volume and pressure information of the system. The algorithm is validated for a single degree-of-freedom soft fluidic actuator. Results indicate that axial forces acting on a single actuator can be estimated with mean error of 0.56 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.66 N within the validated range of 0–6 N in a quasi-static configuration. The force sensing methodology is applied to force control in a single actuator as well as the coupled parallel robot. It can be seen that forces are controllable for both systems, with the capability of controlling directional contact forces in case of the multidegree-of-freedom parallel soft robot.

DFT study of enhancement in nonlinear optical response of exohedrally and endohedrally alkaline earth metals (Be, Mg, Ca) doped adamanzane

AbstractIn this study, density functional theory has been used to investigate the geometric, electronic, linear and nonlinear optical properties of exohedrally and endohedrally doped adamanzane M1(26 adz)M2 where (M1 = M2 = Be, Mg and Ca). The multiple doping rendered excess electrons to the system which resulted in increased HOMO energies and resultantly reduced HOMO‐LUMO gap (from 8.85 eV to 4.87 eV). The significant changes in excitation energy and vertical ionization energy indicated the introduction of excess electrons to the system. The NBO analysis confirmed that both the dopants are electron donating moieties. The formation of new HOMOs were also evident from the density of state (DOS) analysis. The new complexes exhibited remarkable nonlinear optical response and maximum first hyperpolarizability (β = 8.19 × 103 au) and second hyperpolarizability (γ = 8.12 × 105 au) were observed for AM9. This nonlinear response enhanced significantly when materials were placed in the light of 1907 nm wavelength for determination of dynamic hyperpolarizabilities. The UV–Vis analysis confirmed the transparency of designed materials in deep UV region. The structural properties of new materials were also authenticated by IR‐spectra. The exceptionally high nonlinear response makes these materials desirable candidates for photonic, telecommunication and laser applications.

Automated Experiments of Local Non-Linear Behavior in Ferroelectric Materials.

An automated experiment in multimodal imaging to probe structural, chemical, and functional behaviors in complex materials and elucidate the dominant physical mechanisms that control device function is developed and implemented. Here, the emergence of non-linear electromechanical responses in piezoresponse force microscopy (PFM) is explored. Non-linear responses in PFM can originate from multiple mechanisms, including intrinsic material responses often controlled by domain structure, surface topography that affects the mechanical phenomena at the tip-surface junction, and the presence of surface contaminants. Using an automated experiment to probe the origins of non-linear behavior in ferroelectric lead titanate (PTO) and ferroelectric Al0.93 B0.07 N films, it is found that PTO shows asymmetric nonlinear behavior across a/c domain walls and a broadened high nonlinear response region around c/c domain walls. In contrast, for Al0.93 B0.07 N, well-poled regions show high linear piezoelectric responses, when paired with low non-linear responses regions that are multidomain show low linear responses and high nonlinear responses. It is shown that formulating dissimilar exploration strategies in deep kernel learning as alternative hypotheses allows for establishing the preponderant physical mechanisms behind the non-linear behaviors, suggesting that automated experiments can potentially discern between competing physical mechanisms. This technique can also be extended to electron, probe, and chemical imaging.

3D lightweight mechanical metamaterial with nearly isotropic inelastic large deformation response

Well-designed stretching-dominated lattices can form elastic metamaterials with high specific stiffness and strength. Their strongly anisotropic and unstable nonlinear mechanical properties, however, limit their application to energy absorption. In contrast, bending-dominated lattices are well known for high energy absorption capacity and stable nonlinear response, but poor elastic response. Here, we propose a new class of light-weight elastic isotropic bending-dominated truss lattice that combines both advantages. Numerical simulations reveal that the proposed lattices not only exhibit elastic isotropy, but also nearly isotropic inelastic large deformation response. In particular, for a relative density smaller than 1% the metamaterial almost attains the upper bound of Poisson’s ratio for an isotropic material, i.e ν=0.5. Compared to BCC truss lattices, uniaxial compression tests show that the relative modulus is twice as large, and that the relative collapse strength and specific energy absorption are about 1.6 times as large. The designed metamaterial is thus a noteworthy alternative for load bearing, energy absorption, and transformation acoustics.

High Yield Synthesis and Quadratic Nonlinearities of Gold Nanoprisms in Solution: The Role of Corner Sharpness

AbstractSize and shape of noble metal nanoparticles have a major influence on their linear and second order nonlinear properties. Among these nanostructures, acentric objects are expected to display high quadratic nonlinear responses. In this work, a single – step growth of gold nanoprisms (GNPs) was achieved by seedless growth. Their second harmonic response has been investigated experimentally and theoretically with edge length ranging from 40 to 116 nm and for different curvature radii at corners. Their first hyperpolarizabilities β have been measured by Harmonic Light Scattering at 1064 nm. Their calculated and experimental β values are found to display, not only a linear dependence with the surface area as reported for other metallic nanoparticle shapes, but also a strong influence of their corner sharpness on the corresponding nonlinearities. Such high experimental and theoretical β values of GNPs are mainly assigned to the sharpness of tips.

A variational full-network framework with anisotropic damage and viscoelasticity induced by deformation

Incompressible materials, such as filled rubbers and biological tissues, may exhibit high nonlinear and anisotropic inelastic responses induced by deformations when subject to large strains. The constitutive modeling area has focused on describing the anisotropic behavior of viscosity and damage. However, coupled anisotropic inelastic effects are still a major challenge, with few contributions in the literature. This paper then presents a variational full-network framework capable of representing coupled anisotropic damage and viscoelasticity responses induced by deformation. The proposal extends a variational family to include the advantages of the full-network framework to deal with anisotropic behaviors. Approximations of the potential energies used on the full-network integration scheme associate the inelastic scalar variables at each material point with the quadrature points directions, resulting naturally in a set of scalar minimization problems. Numerical tests are presented to show the ability of the framework to represent anisotropic damage and viscoelasticity. Two variational models, specialized for filled rubber and soft biological tissues, are also implemented on finite element software to assess the model into practical applications. The results show the proposed model’s versatility to simulate anisotropic viscoelasticity, anisotropic mechanical damage, and viscous and damage coupled phenomena, maintaining accuracy for large strain and time increments.

Ultrafast Nonlinear Pulse Propagation Dynamics in Metal–Dielectric Periodic Photonic Architectures

Abstract1D metal–dielectric (MD) periodic structures take advantage of large refractive index contrast between metal and dielectrics to invoke extremely high nonlinear ultrafast responses of metal. These structures are also special due to their extremely high laser damage threshold. The Bragg‐like 1D MD structure (Ag/SiO2)4 enables strong optical field confinement with much enhanced nonlinear features as compared to simple metal or single (Ag/SiO2)1 structure. In the present work, the ultrafast nonlinear optical responses of the above structures are investigated via femtosecond broadband optical pump–probe technique. The enhanced nonlinear optical absorption is of reverse saturation of absorption nature, resulted due to free‐carrier absorption and excited‐state absorption processes. The spectral nonlinearities are closely related to the pump‐induced modification of the metal's dielectric functions, which are qualitatively visualized by transfer matrix and two‐temperature models. The ultrafast temporal evolution of nonlinear absorption clearly demonstrates enhanced optical nonlinearity, disentangled by the electron–electron and electron–phonon dynamic interactions at picosecond time scales. A phenomenological pulse propagation model is employed that incorporates the experimentally obtained nonlinear absorption coefficients and different nonlinear effects exhibited by the system. The findings of these new optical materials can possibly pave the way for promising applications in ultrafast photonics.

Investigation and analysis of the optical Kerr nonlinear effect caused by metal nanocomposite on the performance of nonlinear hybrid plasmonic waveguide

In this paper, a nonlinear hybrid plasmonic waveguide (HPW) with a layer of metal-nanocomposite as nonlinear Kerr material with the high nonlinear response, long propagation length and tight light confinement for processing and active control of optical signals for nonlinear applications has been proposed. The effective parameters of the nonlinear layer due to third-order susceptibility in the HPW structure, which includes the nonlinear metal-nanocomposite layer, have been analyzed by using the Maxwell-Garnett theory. The presence of metal nanoparticles in the nanocomposite host medium improves the nonlinear effect of the proposed HPW structure. Also, the effect of radius, volume fraction, host medium permittivity related to nanoparticles and nanocomposite on the performance and output results of effective nonlinearity coefficient, propagation length, effective mode area, confinement factor has been simulated by using FEM numerical solution method in TM mode. The proposed nonlinear hybrid plasmonic waveguide is an ideal option for design and application in nonlinear all-optical integrated circuits.

Spectroscopic fingerprints of gapped quantum spin liquids, both conventional and fractonic

We explain how gapped quantum spin liquids, both conventional and 'fractonic', may be unambiguously diagnosed experimentally using the technique of multidimensional coherent spectroscopy. 'Conventional' gapped quantum spin liquids (e.g. $Z_2$ spin liquid) do not have clear signatures in linear response, but do have clear fingerprints in non-linear response, accessible through the already existing experimental technique of two dimensional coherent spectroscopy. Type I fracton phases (e.g. X-cube) are (surprisingly) even easier to distinguish, with strongly suggestive features even in linear response, and unambiguous signatures in non-linear response. Type II fracton systems, like Haah's code, are most subtle, and may require consideration of high order non-linear response for unambiguous diagnosis.

Nonlinear Mid‐Infrared Metasurface based on a Phase‐Change Material

AbstractThe mid‐wave infrared (MWIR) spectral region (3–5 µm) is important to a vast variety of applications in imaging, sensing, spectroscopy, surgery, and optical communications. Efficient third‐harmonic generation (THG), converting light from the MWIR range into the near‐infrared, a region with mature optical detection and manipulation technologies, offers the opportunity to mitigate a commonly recognized limitation of current MWIR systems. In this work, the possibility of boosting THG in the MWIR through a metasurface design is presented. Specifically, a 30‐fold enhancement in a highly nonlinear phase‐change material Ge2Sb2Se4Te1 (GSST) is demonstrated by patterning arrays of subwavelength cylinders supporting a magnetic dipolar resonance. The unprecedented broadband transparency, large refractive index, and remarkably high nonlinear response, together with unique phase‐change properties, make GSST‐based metasurfaces an appealing solution for reconfigurable and ultra‐compact nonlinear devices operating in the MWIR.

Eco-geomorphological connectivity and coupling interactions at hillslope scale in drylands: Concepts and critical examples

The diagnosis of land degradation requires a deep understanding of ecosystem functioning and evolution. In dryland systems, in particular, research efforts must address the redistribution of scarce resources for vegetation, in a context of high spatial heterogeneity and non-linear response. This fact explains the prevalence of eco-hydrological perspectives interested in runoff processes and, the more recent, focused on connectivity as an indicator of system resource optimisation. From a geomorphological perspective and reviewing the concepts of eco-hydro-geomorphological interactions operating in ecosystems, this paper explores the effects of erosion on vegetation configuration through two case studies at different spatio-temporal scales. We focus on the structure-function linkage, specifically on how morphological traits relate with different stages in the erosional sequence, both in the abiotic and the biotic domain. Results suggest that vegetation dynamics are affected by structural boundary conditions at both scales, i.e. by surface armouring related with rock fragments at the patch scale, and by the degree of hillslope-channel coupling at the hillslope scale. Our preliminary results can serve as new working hypotheses about the structure-function interplay on hillslopes. All this, taking advantage of the recent technological achievements for acquiring very high-resolution geospatial data that offer new analytical possibilities in a range of scales.

FY-3D MERSI On-Orbit Radiometric Calibration from the Lunar View

Limited by the on-orbital calibration capability, scaling the measured radiance in accuracy and stability is challenging for the Earth observation satellites in the reflective solar bands (RSBs). Although the lunar calibration is a well-developed technique in the RSBs, limited work has been done for Chinese Earth observation satellites. To improve the on-orbital calibration performance, the advanced MEdium Resolution Spectral Imager (MERSI II), which is the primary payload of the fourth satellite of the Fengyun 3 Series (FY-3D), expands the space view angle of the imager in order to capture better lunar images. In this study, we propose an absolute radiometric calibration method based on the FY-3D/MERSI lunar observation data. A lunar irradiance model named ROLO/GIRO has been used together with the necessary data procedures, including dark current count estimation, single pixel irradiance calculation, and full disk lunar irradiance calculation. The calibration coefficients obtained by the lunar calibration are compared with the pre-launch laboratory calibration. The results show that the deviations between the two calibration procedures are in a reasonable range in general. However, a relatively high non-linear response was found in the low energy incidence for some detectors, which leads to the large deviation in the corresponding bands. This study explored an ideal and independent method to validate MERSI on-orbit radiometric performance. The lunar calibration practiced for MERSI also gave a valuable example that can be recommended to the other Chinese Earth observation satellites.

Size Dependence of the Resonant Third-Order Nonlinear Refraction of Colloidal PbS Quantum Dots

Due to their high resonant third-order nonlinear response, lead sulfide quantum dots (QDs) are potential materials for applications in the field of nonlinear optics. In this paper, we implement the Z-scan method to study the resonant nonlinear response of lead sulfide QDs in colloidal solutions. We managed to measure the purely intrinsic resonant nonlinear response, free of thermal contribution. We report that the lead sulfide QD third-order nonlinear response per QD shows an unconventional increase. A figure of merit for QD nonlinearity grows as a power function with a factor of 2.9.

Vibrating reed magnetometer studies of superconducting and magnetic materials

ABSTRACTApplications of sensitive vibrating reed magnetometry to a variety of superconducting and magnetic materials are reviewed. The advantages of conducting vibrating reed studies of small single crystals, ceramics, thin films and multilayers with high anisotropy, composition gradients, strain and nonlinear magnetic response are documented. The equilibrium and dynamic properties of magnetic flux in superconductors, and coexistence of magnetic and superconducting states are emphasised. Vibrating reed experiments on Nb, NbSe2, (Ba0.6K0.4)BiO3, HoNi2B2C, {Nb(x)/Ni(y)}Z multilayer films, and κ-(ET)2Cu{N(CN)2}Br have revealed subtle, exotic superconducting behaviours that remain unexplained. Future prospects for vibrating reed measurements of ferromagnetic thin films with patterned nanostructures are considered.

Effect of silver doping on ultrafast broadband nonlinear optical responses in polycrystalline Ag-doped InSe nanofilms at near-infrared.

There is great interest in transition metal-doped InSe because of its high nonlinearity and ultrafast response time at higher light fluence. Herein, Ag-doped InSe nanofilms were precisely manufactured using a direct current-radio frequency sputtering method, and their ultrafast broadband nonlinear optical responses in near-infrared were systematically researched. Ag-doped InSe nanofilm exhibited a broadband nonlinear optical response (800–1100 nm) and ultrafast carrier absorption (<1 ps), and can act as a potential semiconducting material for all-optical devices. Through precise control of the sputtering process parameters, Ag-doped InSe nanofilms were successfully prepared that were smooth, uniform, and exhibited no cracks. Nonlinear optical studies (femtosecond transient absorption spectroscopy and Z-scan measurement) indicated that nonlinear absorption behavior in Ag-doped InSe nanofilm withstands a transformation from saturation absorption to reverse saturation absorption arising from ground state bleaching, free-carrier absorption (FCA), and two-photon absorption (TPA). Additionally, nonlinear refraction behavior in Ag-doped InSe nanofilm was successfully detected near the intrinsic absorption edge, which arose from Kerr refraction and free-carrier refraction. More importantly, the broadband nonlinear response, ultrafast carrier absorption, and carrier recovery time of Ag-doped InSe nanofilm has the ability to controllably tune via Ag doping. Furthermore, Ag-doped InSe nanofilm possesses the nonlinear figure of merit (FOM) of 2.02, which indicates that Ag-doped InSe nanofilm is a promising semiconducting material for all-optical switching devices in near-infrared.

Nanoporous Metallic Network as a Large-Scale 3D Source of Second Harmonic Light

Second harmonic generation (SHG) is forbidden from most bulk metals, because metals are characterized by a net zero electric-field in equilibrium. This limit breaks down when reaching nanoscale dimensions, as have been shown for metallic nano-particles and nano-cavities. Yet, nonlinear response from a three-dimensional (3D) macroscale metallic piece comprising sub-optical wavelength features remains a challenge for many years. Herein, we introduce a largescale nanoporous metallic network whose building-blocks are assembled into an effective nonlinear conductive material, with a considerable conversion efficiency in a wide range of optical wavelengths. The high nonlinear response results from the network structure having a large surface area on which the inversion symmetry is broken. In addition, because of the 3D structure, hot-spots can be formed also in deeper focal plans of the metallic network, and thus can give rise to coherent addition of the signal. The solid connectivity between the nanoscale building-blocks also plays a role, because it forms a robust network which may respond in a collective manner to form very intense hot-spots. Broadband responses of the metallic network are observed both by SHG and cathodoluminescence (CL). The large-scale dimension and generation of randomized hot-spots make this 3D metallic network a promising candidate for applications like photocatalysis, sensing, or in optical imaging as structured illumination microscopy.