Transverse Shift Research Articles

Visualization of the optical spin Hall effect in out-of-plane refraction

The traditional law of refraction defines the incidence plane as the plane including the incident beam wavevector and the surface normal vector at the interface of two different optical media. The optical spin Hall effect (OSHE) refers to the spin-dependent transverse shift of the refracted beam perpendicular to the incidence plane. In this Letter, we demonstrate that OSHE in out-of-plane refraction can be detected and visualized in the far-field, even at small and normal incidence angles. The extent of spin-dependent photon spatial separation induced by anomalous refraction can be customized by manipulating the 2D additive momentum from the metasurface. Experimental visualization of the OSHE confirms the existence of a new, to the best of our knowledge, plane to describe the OSHE of the refracted beam outside the incidence plane.

Scattering of relativistic electrons and analogies with optical phenomena: A study of longitudinal and transverse shifts at step potentials

Scattering of relativistic electrons and analogies with optical phenomena: A study of longitudinal and transverse shifts at step potentials

Coherent control of the photonic spin Hall effect by Er3+ ion concentration in an Er3+-doped YAG crystal

We theoretically investigate the effect of doped Er3+ ion concentration on the spin Hall effect (SHE) of light reflected from a Kretschmann-Raether (K-R) structure. In such a structure, an Er3+-doped yttrium aluminum garnet (YAG) crystal acts as the substrate. The excitation of surface plasmon resonance(SPR) leads to the enhancement of the spin splitting of the reflected beam in the resonance reflection dip. Due to the variation of electric dipole moment and energy level lifetime induced by Er3+ ion concentration, the spin-dependent transverse shift is sensitively dependent upon Er3+ ion concentration. Furthermore, under different concentrations of Er3+ ion, the intensity and detuning of the control field have different effects on the magnitude, sign and position of the transverse shift. More importantly, the photonic SHE can be significantly enhanced via choosing the suitable values of the control intensity and detuning at 15% Er3+ ion concentration. Therefore, our scheme may provide a basis for selecting suitable Er3+ ion concentration to enhance the SHE of light in future integrated systems.

Strong polarization-dependent photonic bandgap and giant photonic spin Hall effect in a one-dimensional photonic crystal entirely composed of all-dielectric metamaterials

In conventional one-dimensional (1-D) photonic crystals (PhCs) consisting of isotropic dielectrics, photonic bandgaps (PBGs) exhibit weak polarization-dependent property since the propagating phase of the isotropic dielectric film is polarization-independent. The weak polarization-dependent property of PBGs intensively impedes the potential application of 1-D PhCs in the photonic spin Hall effect (PSHE). Herein, we investigate the polarization-dependent property of PBGs in a class of 1-D PhCs entirely consisting of all-dielectric elliptical metamaterials (EMMs) called all-EMM 1-D PhCs. Driven by the combination of 1-D PhCs and all-dielectric EMMs, strong polarization-dependent PBGs can be realized. Then, we exploit the strong polarization-dependent PBG to achieve giant PSHE. The enhanced transverse shift of the PSHE reaches the order of 102 μm. Our work not only establishes a bridge between PhCs and all-dielectric metamaterials, but also paves a new route to manipulating polarization of light.

Highly sensitive refractive index, chemical potential, and applied electrical voltage detection in terahertz region with photonic spin Hall effect in a plasmonic sensor based on graphene and germanium layers

"In this work, a transverse spin-dependent shift (SDS) of the horizontal photonic spin Hall effect (PSHE) at a fixed frequency (5 THz) is simulated for detection of refractive index, chemical potential, and applied electrical voltage to a plasmonic sensor with four layers (germanium, organic layer, graphene, and gas medium). The variation of the refractive index of graphene with chemical potential and applied voltage is given from the simulated values. A refractive index resolution (1.73 × 10–12 RIU) is obtained when the refractive index n4 of the analyte layer is changed from 1 RIU to 1.1 RIU when the chemical potential μc is 0.003 eV and the amplified angle ∆ is 0.1°. A chemical potential resolution (6.32 × 10–14 eV) and corresponding voltage resolution (6.83 × 10–13 V) are obtained when the chemical potential is changed from 0.003 eV to 0.03 eV, the refractive index of gas medium n4 is 1.1 RIU and the amplified angle is ∆ = 0.1°. These values are very good in comparison with the situation when the spin Hall effect is not applied (7.47 × 10–6 RIU, 0.001166 eV, and 0.01259 V) for the same values of μc, n4, and ∆."

High-accuracy transverse translation velocimeter enabled by OAM-assisted dual-point transverse Doppler effect

Laser Doppler velocimetry has developed as a powerful enabling technology within a myriad of realistic scenarios. While existing toolkits that exploit optical vortex allow access to longitudinal linear velocimetry and/or transverse rotational velocimetry of a motion object, achieving high-accuracy transverse translation velocimetry is still an open challenge. Here, we overcome this restriction by breaking the prevailing single-point metrological paradigm, instead employing dual-point transverse Doppler effect of customized orbital-angular-momentum (OAM) light fields as our pathway. We show that the dual-point transverse Doppler shifts can be generated and detected in a single velocimetry geometry for the first time, thereby enabling the determination of arbitrary transverse translation velocity. In particular, we demonstrate that the limited frequency resolution causes the velocimetry deviation and increasing the sampling duration can thus effectively improve velocimetry accuracy. As a consequence, a high-accuracy transverse translation velocimeter with a relative error below 0.08% has been well-established. Our validated findings not only provide a profound insight into the interaction of OAM with macroscopic motion object but also may find potential applications in clinical medicine, astronomical observation, and industrial manufacturing.

Modeling of Non-Isothermal Viscoelastic-Viscoplastic Deformation of Bending Reinforced Plates

A model of non-isothermal viscoelastic-viscoplastic deformation of multidirectionally reinforced flexible plates has been developed. The viscoplastic deformation of isotropic materials of the composition is described by the relations of the flow theory with isotropic hardening, which take into account the dependences of the loading functions on temperature and strain rate intensity. The viscoelastic behavior of the composition components is described by the equations of the Maxwell–Boltzmann model. The weakened resistance of reinforced plates to transverse shifts is modeled by the Ambartsumian bending theory relations, and the geometric nonlinearity is modeled in the Karman approximation. The connection between the thermophysical and mechanical components of the problem of inelastic dynamic deformation of reinforced plates is taken into account. The temperature over the thickness of structures is approximated by a 7th order polynomial. The numerical solution of the formulated nonlinear two-dimensional problem is constructed using an explicit scheme of time steps. The viscoelastic-viscoplastic dynamic behavior of a relatively thin glass-plastic plate is studied with and without allowance for the thermal response in it. The structure is loaded transversely with an air blast wave. It is shown that the failure to take into account the thermal response in a fiberglass plate can significantly distort the calculated fields of residual deformations of the components of its composition, despite the fact that the maximum heating of such a structure does not exceed 10°C. Viscoelastic-plastic calculations, when the sensitivity of the composite materials to the rate of their deformation can be neglected, can reasonably be carried out without taking into account the thermal response of the composite plate, if there are no external heat sources of non-mechanical origin.

Tunable optical differential operation based on graphene at a telecommunication wavelength.

Optical differential operation based on the photonic spin Hall effect(SHE) has attracted extensive attention in image processing of edge detection, which has advantages of high speed, parallelism, and low power consumption. Here, we theoretically demonstrate tunable optical differential operation in a four-layered nanostructure of prism-graphene-air gap-substrate. It is shown that the spatial differentiation arises inherently from the photonic SHE. Furthermore, we find that the transverse spin-Hall shift induced by the photonic SHE changes dramatically near the Brewster angle with the incident angle increases at a telecommunication wavelength. Meanwhile, the Fermi energy of graphene and the thickness of the air gap can affect the transverse spin shift. Interestingly, we can easily adjust the Fermi energy of graphene in real time through external electrostatic field biasing, enabling fast edge imaging switching at a telecommunication wavelength. This may provide a potential way for future tunable spin-photonic devices, and open up more possible applications for artificial intelligence, such as target recognition, biomedical imaging, and edge detection.

Anomalous Lateral Optical Force as a Manifestation of the Optical Transverse Spin

AbstractInteracting with an evanescent wave, an achiral particle can experience a lateral optical force (LOF) in a direction which is perpendicular to that of the illuminating photon momentum while the system apparently has the left–right symmetry. Here, using the Cartesian multipole expansion theory, a general relationship between LOF and spin and momentum is established. Most importantly, it is demonstrated that an anomalous LOF exerted on an isotropic achiral particle of arbitrary size and composition is proportional to the optical transverse spin in the incident evanescent wave that carries pure transverse spin associated with spin‐momentum locking. Manifesting itself as a mechanical consequence of the Berry phase effect, this anomalous LOF suggests a direct detectability of the transverse spin of light, as well as mimicking the transverse shift of light in the spin Hall effect of photons.

Giant photonic spin Hall effect empowered by polarization-dependent quasibound states in the continuum in compound grating waveguide structures

The photonic spin Hall effect (PSHE) plays an important role in both fundamental science and precision metrology. In this paper, we theoretically propose a polarization-dependent bound state in the continuum (BIC) in a compound grating waveguide structure based on the selectable guided resonance at near-infrared wavelengths. Empowered by the unique resonant property and polarization-dependent property of the quasi-BIC, the transverse shift of the PSHE can be intensively enhanced to the order of hundreds of micrometers. Besides, the enhancement of the transverse shift of the PSHE is robust against the geometric parameters. Our work not only provides an all-dielectric platform to achieve giant PSHE, but also offers a viable approach to design high-performance PSHE-based optical devices.

Beam deflection and negative drag in a moving nonlinear medium

Light propagating in a moving medium is subject to light drag. While the light drag effect due to the linear refractive index is often negligibly small, the light drag can be enhanced in materials with a large group index. Here we show that the nonlinear refractive index can also play a crucial role in the propagation of light in moving media and results in a beam deflection. We perform an experiment with a rotating ruby crystal that exhibits a very large negative group index and a positive nonlinear refractive index. The negative group index drags the light opposite to the motion of the medium. However, the positive nonlinear refractive index deflects the beam along with the motion of the medium and hinders the observation of the negative drag effect. Hence, we show that it is necessary to measure not only the transverse shift of the beam but also its output angle to discriminate the light drag effect from beam deflection. Our work provides insight into applications for all-optical control of light trajectories, particularly for beam steering, mode sorting, and velocimetry.

Longitudinal and Transverse Optical Beam Shifts Show Non‐separability

AbstractUnder the introduction of any tilted interface in its trajectory, an optical beam experiences polarization‐dependent deflections in the longitudinal and transverse directions with respect to the plane of incidence. The physics of such optical beam shifts are connected to profound universal wave phenomena governed by the fine interference effects of wave packets and have opened up avenues toward metrological applications. Here, the inherent non‐separability of the longitudinal and transverse optical beam shifts is revealed by considering a rather simple case of a partially reflecting Gaussian laser beam from a dielectric interface. This non‐separability appears substantially at some particular regions in the corresponding experimental parameter space. This manifests as a position–position non‐separable state of classical light field. The tunability of the related experimental parameters offers control over the degree of non‐separability. These findings are expected to be a step forward in the exploration of optical beam shifts and a number of analogous universal phenomena. The initial observation also indicates its practical impact on metrology and generation of high‐quality tunable position–position non‐separable states of classical light fields.

Engineered photonic spin Hall effect of Gaussian beam in antisymmetric parity-time metamaterials

A model of the photonic spin Hall effect (PSHE) in antisymmetric parity-time (APT) metamaterials with incidence of Gaussian beams is proposed here. We derive the displacement expression of the PSHE in APT metamaterials based on the transport properties of Gaussian beams in positive and negative refractive index materials. Furthermore, detailed discussions are provided on the APT scattering matrix, eigenstate ratio, and response near exceptional points in the case of loss or gain. In contrast to the unidirectional non-reflection in parity-time (PT) symmetric systems, the transverse shift that arises from both sides of the APT structure is consistent. By effectively adjusting the parameters of APT materials, we achieve giant displacements of the transverse shift. Finally, we present a multi-layer APT structure consisting of alternating left-handed and right-handed materials. By increasing the number of layers, Bragg oscillations can be generated, leading to an increase in resonant peaks in transverse shift. This study presents a new approach to achieving giant transverse shifts in the APT structure. This lays a theoretical foundation for the fabrication of related nano-optical devices.

THE STRUCTURAL ANALYSIS OF THE HOUSING OF THE FREIGHT CAR AXLE BOX

The cars that are operated on the railways of Ukraine are equipped with axle boxes with cylindrical roller bearings. Many years of operating experience has shown that they have insufficient durability. One of the reasons is the uneven distribution of the load between the rollers in the bearings, caused by the design features of the wagon bogies. One of the possible ways to equalize the distribution of loads between the rolling elements can be the creation of a box housing with variable stiffness. The article provides a detailed analysis of existing design solutions. It has been established that the use of aluminum alloys for the manufacture of axle box housings, despite the low specific density of the alloy, is impractical due to their high cost, increased wear of the bearing surfaces, and insufficient service life. The use of rubber as gaskets to create variable stiffness also proved to be impractical. The reason is the inability of rubber to operate at low temperatures in winter. As a result, the destruction of the rubber required additional (unscheduled) axle box repairs. The manufacture of axle box bodies with cavities or grooves of various configurations in order to change the rigidity of the elements of the upper part of the axle box body turned out to be unpromising. The reason was the technological complexity of manufacturing, the difficulty of providing the necessary strength under dynamic loading conditions. The most successful was the design of the box body with two rectangular tides along the edges of the upper part in the roller loading zone. These lugs are located along the entire length of the hull and are the supporting surfaces for transferring the load from the side frame. A promising direction in the 70s of the XX century was the rejection of traditional massive axle boxes and the transition to the use of adapters (half axle boxes). However, this option had to be abandoned at that time due to the impossibility of ensuring reliable sealing of the bearings. At the same time, the modern experience of American railways shows that one of the promising areas for improving the design of roller axle boxes is the use of adapters in freight bogies of wheelsets equipped with cassette bearings. The adapter redistributes the load from the bogie to the cassette bearing, acts as a supporting part of a conventional axle box and limits the longitudinal, transverse and angular shifts of the wheel set relative to the bogie frame. In addition, the adapter allows you to reduce the tare weight of the car. However, the use of adapters is possible only if the bearings themselves are reliably sealed. Also, a promising direction can be considered the creation of a box body with variable stiffness, including the use of rubber-metal elements. Keywords: freight car, axle box, housing, bearing, adapter, support surface, actuation.

Ionosphere induced spatial Imbert Fedorov shifts

The reflection and transmission of radio waves are two most common techniques used to study the ionosphere. Considering an electromagnetic wave with a finite diameter, however, displacements and deflections different from the predictions of geometric optics arise. In this paper, we investigate thru calculations one type of these shifts, the out-of-plane Imbert-Fedorov (IF) displacements, induced by the ionosphere on the reflected radio waves. We model the ionosphere as a simple collection of electrons moving in a uniform magnetic field and use the resulting dispersive expressions to calculate the corresponding IF shifts. Since the ionosphere is a dispersive medium, we consider three cases: (1) metallic, (2) dielectric and (3) epsilon-near-zero (ENZ) behavior of the layer. We determine that there exists non-zero differential spatial IF shifts for all the three cases and find that the maximum shift of up to 95 m occurs when the ionosphere acts like an ENZ medium. Finally, we show that these transverse shifts are measurable and discuss how these can be utilized as a potential tool to profile the ionosphere using reflected radio waves.

Current-induced switching of photonic spin Hall effect in a magnetic insulator based on spin–orbit torques

The photonic spin Hall effect (PSHE) is analogous to the electronic spin Hall effect, which has substantial potential for optoelectronic applications. However, PSHE-based devices are rarely studied, and manipulating the PSHE by charge current has remained elusive thus far. In this paper, we demonstrate current-induced switching of PSHE in the Ce1Dy2Al0.42Fe4.58O12 thin film capping with Pt electrodes, which is mediated by spin–orbit torques at the Pt/Ce1Dy2Al0.42Fe4.58O12 interface. The results show that the transverse beam shifts related to the PSHE can be reversed by applying a small order of magnitude charge current (∼108 A·m−2) to the Pt layer in opposite directions, which predicts low dissipation in our proposed heterostructure. In addition, by applying an in-plane magnetic field, the saturation beam shifts can be increased, which can significantly enhance the switching ratio.

Quantification of the Real Plasmonic Field Transverse Distribution in a Nanocavity Using the Vibrational Stark Effect.

Quantifying the real plasmonic field strength experimentally has been long pursued in expanding the applications related to plasmonic enhancement. However, it is still an enormous challenge to determine the inhomogeneous plasmonic field distribution. Here, self-assembled monolayers (SAMs) of 4-mercaptobenzonitrile (MBN) are sandwiched as a gap spacer in a nanoparticle-on-mirror (NPoM) structure, effectively forming ultrahigh field enhancement to observe Stark shifts of the chemical bond. Transverse position-dependent Stark shifts of ν(C═C) and ν(C≡N) in the individual nanocavity measured by surface-enhanced Raman scattering (SERS) experiment combined with the Stark tuning rate by density functional theory (DFT) simulation accurately revealed the inhomogeneous plasmonic field transverse distribution and quantified the transverse plasmonic field strength up to ∼1.9 × 109 V/m, which matches the value predicted by finite element method (FEM) simulation. This work deepens the insight into plasmon-based technologies and will coordinate high-resolution techniques such as tip-enhanced Raman spectroscopy (TESR) to reveal the real plasmonic field distribution.

DNA base order parameter determination without influence of chemical exchange.

Nuclear magnetic resonance (NMR) spectroscopy is a versatile tool used to investigate the dynamic properties of biological macromolecules and their complexes. NMR relaxation data can provide order parameters S2, which represent the mobility of bond vectors reorienting within a molecular frame. Determination of S2 parameters typically involves the use of transverse NMR relaxation rates. However, the accuracy in S2 determination can be diminished by elevation of the transverse relaxation rates through conformational or chemical exchange involving protonation/deprotonation or non-Watson-Crick base-pair states of nucleic acids. Here, we propose an approach for determination of S2 parameters without the influence of exchange processes. This approach utilizes transverse and longitudinal 13C chemical shift anisotropy (CSA) - dipole-dipole (DD) cross-correlation rates instead of 13C transverse relaxation rates. Anisotropy in rotational diffusion is taken into consideration. An application of this approach to nucleotide base CH groups of a uniformly 13C/15N-labeled DNA duplex is demonstrated.

Transverse Doppler effect due to Gaussian beams.

We report on the observation of a transverse Doppler shift in the optical domain. It occurs when a receiving system travels perpendicularly to the propagation direction of a Gaussian beam. Shifts of a few tens of Hz have been evidence for a detector moving in the mm/s range. The shift increases as the detector is far from the beam axis. The observations fully agree with theoretical calculations on the propagation of Gaussian beams. It can be observed for any kind of waves, including radio and acoustic waves. Practical consequences are then discussed, especially for techniques using Doppler measurements in microsystems.

An Ultracompact Angular Displacement Sensor Based on the Talbot Effect of Optical Microgratings.

Here, we report an ultracompact angular displacement sensor based on the Talbot effect of optical microgratings. Periodic Talbot interference patterns were obtained behind an upper optical grating. By putting another grating within the Talbot region, the total transmission of the two-grating structure was found to be approximatively in a linear relationship with the relative pitch angle between the two gratings, which was explained by a transversal shift of the Talbot interference patterns. The influence of the grating parameters (e.g., the grating period, the number of grating lines and the gap between the two gratings) was also studied in both a simulation and an experiment, showing a tunable sensitivity and range by simply changing the grating parameters. A sensitivity of 0.19 mV/arcsec was experimentally obtained, leading to a relative sensitivity of 0.27%/arcsec within a linear range of ±396 arcsec with the 2 μm-period optical gratings. Benefitting from tunable properties and an ultracompact structure, we believe that the proposed sensor shows great potential in applications such as aviation, navigation, robotics and manufacturing engineering.