Nonlinear Rotation Research Articles

Improved temporal characteristics for post-compressed pulses via application-tailored nonlinear polarization ellipse rotation.

Intense ultrashort laser pulses with high temporal quality are essential for fundamental science. Nonlinear polarization ellipse rotation (NER) is one way to ensure this high temporal quality, by suppressing weaker signals beyond the duration of the main pulse up to a few orders of magnitude. Post-compression schemes have revolutionized ultrafast lasers, enabling the generation of pulses with durations beyond the limit supported by laser gain media. However, high compression ratios lead to the formation of new pre- and post-pulses. Both NER and post-compression depend on the optical Kerr effect. This makes the combination of the two in a single setup both advantageous and straightforward. While NER cannot suppress the new pre- and post-pulses generated in post-compression, we show via simulations and experimental data that by combining the two, it is possible to shape the output spectrum and counteract temporal contrast degradation.

Hidden vortices and Feynman rule in Bose-Einstein condensates with density-dependent gauge potential.

In this paper, we numerically investigate the vortex nucleation in a Bose-Einstein condensate (BEC) trapped in a double-well potential and subjected to a density-dependent gauge potential. A rotating Bose-Einstein condensate, when confined in a double-well potential, not only gives rise to visible vortices but also produces hidden vortices. We have empirically developed Feynman's rule for the number of vortices versus angular momentum in Bose-Einstein condensates in the presence of density-dependent gauge potentials. The variation of the average angular momentum with the number of vortices is also sensitive to the nature of the nonlinear rotation due to the density-dependent gauge potentials. The empirical result agrees well with the numerical simulations and the connection is verified by means of curve-fitting analysis. The modified Feynman rule is further confirmed for the BECs confined in harmonic and toroidal traps. In addition, we show the nucleation of vortices in double-well and toroidally confined Bose-Einstein condensates solely through nonlinear rotations (without any trap rotation) arising through the density-dependent gauge potential.

Bio-Inspired Helicoidal Composite Structure Featuring Graded Variable Ply Pitch under Transverse Tensile Loading

Biostructures found in nature exhibit remarkable strength, toughness, and damage resistance, achieved over millions of years. Observing nature closely might help develop laminates that resemble natural structures more closely, potentially improving strength and mimicking natural principles. Bio-inspired Carbon Fiber-Reinforced Polymers (CFRP) investigated thus far exhibit consistent pitch angles between layers, whereas natural structures display gradual variations in pitch angle rather than consistency. Therefore, this study explores helicoidal CFRP laminates, focusing on the Non-Linear Rotation Angle (NLRA) or gradual variation to enhance composite material performance. In addition, it compares the strength and failure mechanisms of the gradual configuration with conventional helicoidal and unidirectional (UD) laminates, serving as references while conducting transverse tensile tests (out-of-plane tensile). The findings highlight the potential of conventional and gradual helicoidal structures in reinforcing CFRP laminates, increasing the failure load compared to unidirectional CFRP laminate by about 5% and 17%, respectively. In addition, utilizing bio-inspired configurations has shown promising improvements in toughness compared to traditional unidirectional laminates, as evidenced by the increased displacement at failure. The numerical and experimental analyses revealed a shift in crack path when utilizing the bio-inspired helicoidal stacking sequence. Validated by experimental data, this alteration demonstrates longer and more intricate crack propagation, ultimately leading to increased transverse strength.

Experimental evaluation and numerical investigation on the anti-collapse performance of beam-to-column connections in the minor-axis direction

This study examined the effects of structural resistance in both major- and minor-axis directions on the anti-collapse performance of a fully bolted composite frame. Current research in the field has focused predominantly on the anti-collapse performance of H-columns in the major-axis direction, potentially hindering accurate determination of anti-collapse transmission path within a structure. Herein, monotonic static loading experiments were conducted on two substructures in the minor-axis direction: one equipped with welded flange and bolted web connections and the other with fully bolted connections. The ductility development curve, dynamic collapse response curve, and resistance mechanism correlation curve were employed to evaluate the test results. Fully bolted connections exhibited superior nonlinear rotation capacity, which is essential for the development of a structure's catenary resistance The failure mechanisms and resistance development processes of the structures were reproduced using the ABAQUS/Explicit dynamic quasi-static modeling technique. A full-scale finite element model was developed for the frame with fully bolted connections loaded in the minor-axis direction. This research will contribute to the robust design of fully bolted structural frames that considers the effects of the column stiffness, thickness of the splicing cover plate, number of bolt rows, and bolt apertures of flange connections on deformation and resistance to loading in the minor-axis direction.

Measuring non-linear Faraday rotation in cold atoms in presence of persistent transverse fields using tunable differential imaging

Non-linear Faraday rotation in cold atoms promises precision magnetometry due to narrower magnetic resonance linewidth compared to the linear Faraday effect. Imaging techniques based on linear Faraday effect have emerged as a tool to characterize the dynamics of ultracold atomic clouds. Using a camera instead of balanced detectors, we can obtain the spatial distribution of polarization rotation in a uniformly intense optical beam. However, the finite dynamic range of the imaging device limits the sensitivity to measure non-linear Faraday rotation at a given incident power. Here, we experimentally demonstrate a differential imaging technique in which we can tune parameters to improve contrast and the sensitivity to the non-linear Faraday rotation signal by a factor of ≈7 over existing imaging methods. The atomic cloud experiences a uniform optical field even when shifted by persistent magnetic fields making the method robust. This allows us to study the effect of transverse fields on non-linear Faraday rotation in ultra-cold atoms, paving the way toward spatially resolved vector magnetometry.

23 KHz linewidth 1064 nm SOA based fiber laser by using parallel type subring cavities

This study presents a high-quality fiber ring laser created by integrating a semiconductor optical amplifier to generate amplified spontaneous emission with a four-subring resonator and utilizing the nonlinear polarization rotator effect. When the driven current of 400 mA, the laser exhibited a maximum power deviation of 0.204 dB and a wavelength deviation of 0.012 nm during a one-hour testing period. Furthermore, utilizing a delayed self-heterodyne measurement system, we measured the linewidth of the self-made fiber laser to be 23 kHz.

Magnetic nanoparticles detection based on nonlinear Faraday rotation

Magnetic nanoparticles (MNPs) have attracted interest in various research fields due to their special superparamagnetic and strong magneto-optical effects, especially as contrast agents for enhancing medical imaging contrast. Using MNPs capable of generating Faraday rotation angles with higher harmonics as magnetic-optical contrast agents allows for a distinct contrast with biological tissues lacking these higher harmonics. This significantly improves the sensitivity of magnetic-optical imaging. By introducing the interaction coefficient, we propose a model for the nonlinear Faraday rotation of MNPs under the excitation of an external alternating magnetic field. Using our homemade device (which can detect rotation angles as low as approximately 2e-7 rad), we have verified that the higher harmonics of the Faraday rotation can mitigate interference from paramagnetic and diamagnetic backgrounds at lower concentrations. In the future, it is anticipated that MNPs can be utilized as magneto-optical contrast agents to achieve high-resolution in vivo imaging.

Giant nonlinear Faraday rotation in iron doped CdMnTe

Polarization rotation is an important parameter in the design of passive and active photonic components (optical isolators, magneto-optical valves, and magnetic field sensors). This effect is particularly important in materials with delocalized electrons and large atomic orbital moments like CdMnTe, which is an excellent candidate due to its large Zeeman splitting that gives rise to large Faraday rotation. In this paper we report a giant intensity dependent nonlinear Faraday rotation in iron doped Cd0.85Mn0.15Te:Fe crystal. Rotation on the order of 12o in magnetic field of the order of 0.55 T and intensities of 1.832 GW/cm2 can be achieved in a 1.9 mm thick sample. This is 60 time larger in magnitude than previously reported values. In large magnetic field, this intensity dependent rotation will be able to compete with two photon absorption in large magnetic fields, and enhance the linear faraday rotation.

Electrically tunable nonlinear Faraday ellipticity and rotation in WTe$$_2$$

Electrically tunable nonlinear Faraday ellipticity and rotation in WTe$$_2$$

Математическая модель формообразования циклической и каналовой поверхностей на основе нелинейного вращения

This work is a continuation of the series of works by the authors devoted to the issues of shaping surfaces of nonlinear rotation. The geometric scheme for the formation of surfaces of this class includes: an axis of nonlinear rotation, which is a smooth, generally spatial curve, and a forming line, also a smooth spatial curve. When the generating line rotates relative to the curvilinear axis, each point of the generating line describes a circumferential trajectory in the corresponding normal plane of the rotation axis. As a result, a surface of nonlinear rotation is formed, which is a normal cyclic surface. In this work, in order to develop the research results previously obtained by the authors in the field of shaping surfaces of nonlinear rotation, the solution to the inverse problem of shaping is considered and a mathematical justification is given for the possibility of shaping a channel surface based on solutions to the direct and inverse problems. The work provides numerical examples of the formation of the surfaces under consideration, accompanied by mathematical models of surfaces, their computer implementation and visualization. The research results can be useful in the development of CAD systems that involve the design of surface forms of products based on cyclic and channel surfaces in mechanical engineering, construction, architecture and other practical fields.

Nonlinear Rotations on a 3-Dimensional Lattice

The study of resonances of Hamiltonian systems with a divided phase space is a well-established area of research which attracted the interests of many researchers over the years. We study such resonances over a discrete space focusing on the rotational motion of some orbits in the 3-Dimensional lattice, ?3. In this study, we construct the discrete standard map from 2-Dimensional to 3-Dimensional lattices. Then, we identify and categorize any transformation that could give periodicity for the 3-Dimensional lattice on a specific map. The study aims to determine the points that give the periodicity and at the same time investigate the behavior of the points for the nonlinear stable orbits over a discrete space. For some choice of parameters ???? ?, our findings showed that the orbit of the 3-Dimensional map is periodic depending on the initial conditions. Some arbitrary initial conditions may be periodic in a 3-Dimensional lattice.Keywords: Hamiltonian systems, nonlinear rotations, space discretization, arithmetic dynamics

Simultaneous nonlinear spectral broadening and temporal contrast enhancement of ultrashort pulses in a multi-pass cell

We study both numerically and experimentally the use of two third-order nonlinear temporal filtering techniques, namely nonlinear ellipse rotation and cross-polarized wave generation, for simultaneous nonlinear spectral broadening and temporal contrast enhancement of mJ energy, 30 fs titanium:sapphire laser pulses in a multi-pass cell. In both cases, a contrast enhancement greater than 3 orders of magnitude is observed, together with record high conversion efficiencies. Careful balancing of nonlinearity and dispersion inside the multi-pass cell helps tune the spectral broadening process and control the post-compressed pulse duration for specific applications.

Extrinsic Nonlinear Kerr Rotation in Topological Materials under a Magnetic Field.

Topological properties in quantum materials are often governed by symmetry and tuned by crystal structure and external fields, and hence, symmetry-sensitive nonlinear optical measurements in a magnetic field are a valuable probe. Here, we report nonlinear magneto-optical second harmonic generation (SHG) studies of nonmagnetic topological materials including bilayer WTe2, monolayer WSe2, and bulk TaAs. The polarization-resolved patterns of optical SHG under a magnetic field show nonlinear Kerr rotation in these time-reversal symmetric materials. For materials with 3-fold rotational symmetric lattice structure, the SHG polarization pattern rotates just slightly in a magnetic field, whereas in those with mirror or 2-fold rotational symmetry, the SHG polarization pattern rotates greatly and distorts. These different magneto-SHG characters can be understood by considering the superposition of the magnetic field-induced time-noninvariant nonlinear optical tensor and the crystal-structure-based time-invariant counterpart. The situation is further clarified by scrutinizing the Faraday rotation, whose subtle interplay with crystal symmetry accounts for the diverse behavior of the extrinsic nonlinear Kerr rotation in different materials. Our work illustrates the application of magneto-SHG techniques to directly probe nontrivial topological properties, and underlines the importance of minimizing extrinsic nonlinear Kerr rotation in polarization-resolved magneto-optical studies.

Influence of Au on the nucleation of Ag nanoparticles in GeO2-PbO glasses and characterization of their ultrafast third-order nonlinear responses within the plasmon resonance region

Germanate (GeO2-PbO) glasses doped with AgNO3 and co-doped with AgNO3 and Au2O3 were synthesized via melting-quenching technique. Silver nanoparticles were nucleated within the sample doped only with AgNO3 and its plasmon resonance was characterized. The influence of the addition of Au2O3 on the silver nanoparticles nucleation and on the spectroscopic properties of the produced composite materials were investigated using TEM, STEM and UV–Vis spectroscopy. Using the nonlinear ellipse rotation technique, the pure electronic contribution to the samples nonlinear refraction and absorption were characterized within the visible range, including the localized surface plasmon (LSP) resonance wavelength of the metallic nanoparticles. The real and imaginary parts of the third-order nonlinear susceptibility of the glass, composite samples and of the individual nanoparticles were also obtained. In addition, all-optical switching figures of merit of the samples were also calculated. From these results, the dispersion curves of the electronic contribution to the third-order susceptibility of the metallic nanoparticles were obtained and two figures of merit for all-optical switching of the composite materials were calculated. The studied samples are potential candidates for all-optical switching applications with exception to the one with the highest volume filling factor, whose linear and nonlinear absorption coefficients associated to the local field factor deplete the material performance around the LSP resonance wavelength. As far as we know nonlinear ellipse rotation technique was not used before to evaluate the influence of metallic nanoparticles on the nonlinear optical properties of glasses.

A Wideband Polarization Observation of Hydra A with the Jansky Very Large Array

We present the results of a wideband high-resolution polarization study of Hydra A, one of the most luminous FR I radio galaxies known and among the most well studied. The radio emission from this source displays extremely large Faraday rotation measures (RMs), ranging from −12,300 rad m−2 to 5000 rad m−2, the majority of which are believed to originate from magnetized thermal gas external to the radio tails. The radio emission from both tails strongly depolarizes with decreasing frequency. Depolarization, as a function of wavelength, is commonly nonmonotonic, often showing oscillatory behavior, with strongly nonlinear rotation of the polarization position angle with λ 2. A simple model, based on the RM screen derived from the high-frequency, high-resolution data, predicts the lower frequency depolarization remarkably well. The success of this model indicates the majority of the depolarization can be attributed to fluctuations in the magnetic field on scales <1500 pc, suggesting the presence of turbulent magnetic field/electron density structures on subkiloparsec scales within a Faraday rotating medium.

Component method applied to base plate connections of steel racks

This paper deals with the analytical prediction of the rotational strength and stiffness of base plate connections in steel storage racks under bending moment and axial compressive force. Based on the testing prescriptions of the European Code EN15512 and on the findings of an experimental campaign on 21 full scale specimens tested at four different values of constant axial force and under two different types of connection set-up, an analytical procedure relying on the component method is proposed to estimate the rotational strength and stiffness of all load bearing components, and, by suitable assembly of the contributing parts, to obtain a prediction of the overall strength and stiffness of the connection.The aim is to contribute to the definition of improved analytical tools of possible use in the design and product development stage or in the update of existing design codes.Quantitative results are, however, still mixed. Further investigations appear to be required for the stiffness, mainly to describe the nonlinear moment rotation curves observed in the experiments. Strength results are more accurate and as well successful in predicting the failure mode and the loss of strength with increasing compression.

Single-beam technique for ultrashort pulse characterization based on the nonlinear ellipse rotation signal

We present a single-beam method based on the third-order nonlinear-ellipse-rotation (NER) measurement in thick samples to determine the pulse properties, including the duration and linear chirp. Our approach exploits the influence of the intrinsic second-order dispersions of the nonlinear materials, which affect the NER signal as a function of propagation. Two advantages can be highlighted: no delay line is required, and there are no phase-matching issues. To test our method, we characterized ultrafast chirped pulses from a Ti:sapphire amplified laser system and tunable pulses from an optical parametric amplifier using two samples with high dispersions and nonlinearities: SF6 and LaSF-N30 optical glasses.

Crack modes and toughening mechanism of a bioinspired helicoidal recursive composite with nonlinear recursive rotation angle-based layups

The rotation angle is an important parameter affecting the performance of helical structures, and helical structures with nonlinearly increasing rotation angles have been studied. The fracture behavior of a 3D-printed helicoidal recursive (HR) composite with nonlinear rotation angle-based layups was investigated by performing quasistatic three-point bending experiments and simulations. First, the crack propagation paths during the loading of the samples were observed, and the critical deformation displacements and fracture toughness were calculated. It was found that the crack path that propagated along the soft phase increased the critical failure displacement and toughness of the samples. Then, the deformation and interlayer stress distribution of the helical structure under static loading were obtained by finite element simulation. The results showed that the variation in the rotation angle between the layers caused different degrees of shear deformation at the interface between adjacent layers, resulting in different shear stress distributions and thus different crack modes of the HR structures. The mixed-mode I + II cracks induced crack deflection, which slowed the eventual failure of the sample and improved the fracture toughness.

Vortex nucleation in rotating Bose-Einstein condensates with density-dependent gauge potential.

We study numerically the vortex dynamics and vortex-lattice formation in a rotating density-dependent Bose-Einstein condensate (BEC), characterized by the presence of nonlinear rotation. By varying the strength of nonlinear rotation in density-dependent BECs, we calculate the critical frequency, Ω_{cr}, for vortex nucleation both in adiabatic and sudden external trap rotations. The nonlinear rotation modifies the extent of deformation experienced by the BEC due to the trap and shifts the Ω_{cr} values for vortex nucleation. The critical frequencies, and thereby the transition to vortex-lattices in an adiabatic rotation ramp, depend on conventional s-wave scattering lengths through the strength of nonlinear rotation, C, such that Ω_{cr}(C>0)<Ω_{cr}(C=0)<Ω_{cr}(C<0). In an analogous manner, the critical ellipticity (ε_{cr}) for vortex nucleation during an adiabatic introduction of trap ellipticity (ε) depends on the nature of nonlinear rotation besides trap rotation frequency. The nonlinear rotation additionally affects the vortex-vortex interactions and the motion of the vortices through the condensate by altering the strength of Magnus force on them. The combined result of these nonlinear effects is the formation of the non-Abrikosov vortex-lattices and ring-vortex arrangements in the density-dependent BECs.

A Computational Study on Magnetohydrodynamics Stagnation Point Flow of Micropolar Fluids with Buoyancy and Thermal Radiation due to a Vertical Stretching Surface

In current analysis, A numerical approach for magnetohydrodynamics Stagnation point flow of Micropolar fluid due to a vertical stretching Surface is reported. The impact of buoyancy forces is considered. In additions the effects of the thermal radiation and thermal conductivity with non-zero mass flux have been analyzed. we implement the dimensionless variable technique and the systems of coupled non-linear PDEs are transformed into ODEs by using the appropriate similarity technique. Moreover, by using package ND-Solve on Mathematica problem is numerically integrated with the help of shooting technique. Numerical approach for magnetohydrodynamics Stagnation point flow of thermal Radiative Micropolar fluid due to a vertical stretching Surface. The impact of thermophoresis and Brownian motion are considered. We implement the dimensionless variable technique and the systems of coupled non-linear PDEs are transformed into ODEs by using the appropriate similarity technique. To observe the influence of the physical parameters, graphically valuations are performed for numerous emerging parameters like Brownian motion, mixed convection parameters, thermophoresis diffusion, Hartman number, Radiation parameter, Prandtl number, Stretching parameter and other dimension less parameters. These several protuberant parameters of interest are engaged for velocity, temperature and nonlinear micro rotation profile and studied in detail.