arXiv subjects

Weixing Shu

Publications and source records attributed to Weixing Shu.

At least 19 recordsLinked to original sources

arXiv2025

Noncommutative metasurfaces enabled diverse quantum path entanglement of structured photons

Quantum entanglement, a fundamental concept in quantum mechanics, lies at the heart of many current and future quantum technologies. A pivotal task is generation and control of diverse quantum entangled states in a more compact and flexible manner. Here, we introduce an approach to achieve diverse path entanglement by exploiting the interaction between noncommutative metasurfaces and entangled photons. Different from other path entanglement, our quantum path entanglement is evolvement path entanglement of photons on Poincar\'e sphere. Due to quantum entanglement between idler photons and structured signal photons, evolvement path of idler photons on the fundamental Poincar\'e sphere can be nonlocally mirrored by structured signal photons on any high-order Poincar\'e sphere, resulting in quantum path entanglement. Benefiting from noncommutative metasurfaces, diverse quantum path entanglement can be switched across different higher-order Poincar\'e spheres using distinct combination sequences of metasurfaces. Our method allows for the tuning of diverse quantum path entanglement across a broad spectrum of quantum states, offering a significant advancement in the manipulation of quantum entanglement.

physics.optics↗

arXiv2019

Broadband Optical Fully Differential Operation Based on the Spin-orbit Interaction of Light

Optical technology may provide important architectures for future computing, such as analog optical computing and image processing. Compared with traditional electric operation, optical operation has shown some unique advantages including faster operating speeds and lower power consumption. Here, we propose an optical full differentiator based on the spin-orbit interaction of light at a simple optical interface. The broadband optical operation is independent on the wavelength due to the nature of purely geometric. As an important application of the fully differential operation, the broadband image processing of edge detection is demonstrated. By adjusting the polarization of the incident beam, the one-dimension edge imaging at any desirable direction can be obtained. The broadband image processing of edge detection provides possible applications in autonomous driving, target recognition, microscopic imaging, and augmented reality.

physics.optics↗

arXiv2019

Precision Measurement of the Optical Conductivity of Atomically Thin Crystals via Photonic Spin Hall Effect

How to measure the optical conductivity of atomically thin crystals is an important but challenging issue due to the weak light-matter interaction at the atomic scale. Photonic spin Hall effect, as a fundamental physical effect in light-matter interaction, is extremely sensitive to the optical conductivity of atomically thin crystals. Here, we report a precision measurement of the optical conductivity of graphene, where the photonic spin Hall effect acts as a measurement pointer. By incorporating with the weak-value amplification technique, the optical conductivity of monolayer graphene taken as a universal constant of $(0.993\pm0.005)σ_0$ is detected, and a high measuring resolution with $1.5\times10^{-8}Ω^{-1}$ is obtained. For few-layer graphene without twist, we find that the conductivities increase linearly with layer number. Our idea could provide an important measurement technique for probing other parameters of atomically thin crystals, such as magneto-optical constant, circular dichroism, and optical nonlinear coefficient.

physics.optics↗

arXiv2017

Quantized photonic spin Hall effect in graphene

We examine the photonic spin Hall effect (SHE) in a graphene-substrate system with the presence of external magnetic field. In the quantum Hall regime, we demonstrate that the in-plane and transverse spin-dependent splittings in photonic SHE exhibit different quantized behaviors. The quantized SHE can be described as a consequence of a quantized geometric phase (Berry phase), which corresponds to the quantized spin-orbit interaction. Furthermore, an experimental scheme based on quantum weak value amplification is proposed to detect the quantized SHE in terahertz frequency regime. By incorporating the quantum weak measurement techniques, the quantized photonic SHE holds great promise for detecting quantized Hall conductivity and Berry phase. These results may bridge the gap between the electronic SHE and photonic SHE in graphene.

physics.optics↗

arXiv2014

Realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect

We report the realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect. By breaking the rotational symmetry of a cylindrical vector beam, the intrinsic vortex phases that the two spin components of the vector beam carries, which is similar to the geometric Pancharatnam-Berry phase, is no longer continuous in the azimuthal direction, and leads to observation of spin accumulation at the opposite edge of the beam. Due to the inherent nature of the phase and independency of light-matter interaction, the observed photonic spin Hall effect is intrinsic. Modulating the topological charge of the vector beam, the spin-dependent splitting can be enhanced and the direction of spin accumulation is switchable. Our findings may provide a possible route for generation and manipulation of spin-polarized photons, and enables spin-based photonics applications.

physics.optics↗

arXiv2014

Realization of Tunable Photonic Spin Hall Effect by Tailoring the Pancharatnam-Berry Phase

Recent developments in the field of photonic spin Hall effect (SHE) offer new opportunities for advantageous measurement of the optical parameters (refractive index, thickness, etc.) of nanostructures and enable spin-based photonics applications in the future. However, it remains a challenge to develop a tunable photonic SHE with any desired spin-dependent splitting for generation and manipulation of spin-polarized photons. Here, we demonstrate experimentally a scheme to realize the photonic SHE tunably by tailoring the space-variant Pancharatnam-Berry phase (PBP). It is shown that light beams whose polarization with a tunable spatial inhomogeneity can contribute to steering the space-variant PBP which creates a spin-dependent geometric phase gradient, thereby possibly realizing a tunable photonic SHE with any desired spin-dependent splitting. Our scheme provides a convenient method to manipulate the spin photon. The results can be extrapolated to other physical system with similar topological origins.

physics.optics↗

arXiv2012

Method for arbitrary phase transformation by a slab based on transformation optics and the principle of equal optical path

The optical path lengths travelled by rays across a wavefront essentially determine the resulting phase front irrespective of the shape of a medium according to the principle of equal optical path. Thereupon we propose a method for the transformation between two arbitrary wavefronts by a slab, i.e. the profile of the spatial separation between the two wavefronts is taken to be transformed to a plane surface. Interestingly, for the mutual conversion between planar and curved wavefronts, the method reduce to an inverse transformation method in which it is the reversed shape of the desired wavefront that is converted to a planar one. As an application, three kinds of phase transformation are realized and it is found that the transformation on phase is able to realize some important properties such as phase reversal or compensation, focusing, and expanding or compressing beams, which are further confirmed by numerical simulations. The slab can be applied to realizing compact electromagnetic devices for which the values of the refractive index or the permittivity and permeability can be high or low, positive or negative, or near zero, depending on the choice of coordinate transformations.

physics.optics↗

arXiv2012

Generation of optical beams with desirable orbital angular momenta by transformation media

We propose a scheme to controllably convert the wavefront of an arbitrary incident beam into a helical one by compact transformation slabs, thus enabling the output beam to carry desirable orbital angular momentum (OAM). First, based on transformation optics, a three-dimensional (3D) phase transformation between any two wavefronts by °at transformation media is established and then used to mold a wavefront of Gaussian beam into a helical one. Second, 3D FDTD simulations are performed to confirm the spiraling evolutions of the resultant field and phase, clearly demonstrating OAM generated. Further theoretical analyses show that the refractive index exhibiting a helical distribution leads to the oppositely spiral phase front and that it is feasible to produce desirable OAM by generators of unit OAM. The results not only provide an additional way to manipulate phase and photon OAM, but reciprocally shed further light on the phase structure of helical beams, which leads to a new transformation way by a surface.

physics.optics↗

arXiv2011

Enhanced and switchable spin Hall effect of light near the Brewster angle on reflection

We reveal an enhanced and switchable spin Hall effect (SHE) of light near Brewster angle on reflection both theoretically and experimentally. The obtained spin-dependent splitting reaches 3200nm near Brewster angle, 50 times larger than the previous reported values in refraction. We find that the amplifying factor in week measurement is not a constant which is significantly different from that in refraction. As an analogy of SHE in electronic system, a switchable spin accumulation in SHE of light is detected. We were able to switch the direction of the spin accumulations by slightly adjusting the incident angle.

physics.optics↗

arXiv2011

Enhancing or suppressing spin Hall effect of light in layered nanostructures

The spin Hall effect (SHE) of light in layered nanostructures is investigated theoretically in this paper. A general propagation model describing the spin-dependent transverse splitting in the SHE of light is established from the viewpoint of classical electrodynamics. We show that the transverse displacement of wave-packet centroid can be tuned to either a negative or a positive value, or even zero, by just adjusting the structure parameters, suggesting that the SHE of light in layered nanostructures can be enhanced or suppressed in a desired way. The inherent secret behind this interesting phenomenon is the optical Fabry-Perot resonance in the layered nanostructure. We believe that these findings will open the possibility for developing new nano-photonic devices.

physics.optics↗

arXiv2011

Spin-to-orbital angular momentum conversion in spin Hall effect of light

From the viewpoint of classical electrodynamics, we identify the role of spin-to-orbital angular momentum conversion in spin Hall effect of light (SHE). We introduce a distinct separation between spin and orbital angular momenta to clarify the spin-orbital interaction in the SHE of light. We demonstrate that the refractive index gradient can enhance or suppress the spin-to-orbital angular momentum conversion, and thus can control the SHE of light in conventional beam refraction. We suggest that the metamaterial whose refractive index can be tailored arbitrarily may become a good candidate for amplifying or eliminating the SHE of light, and by properly facilitating the spin-to-orbital angular momentum conversion the SHE may be enhanced dramatically. The transverse shifts governed by the spin-to-orbital angular momentum conversion, provide us a clear physical picture to clarify the role of refractive index gradient in the SHE of light. These findings provide a pathway for modulating the SHE of light and can be extrapolated to other physical systems.

physics.optics↗

arXiv2010

Spin Hall effect of light in photon tunneling

We resolve the breakdown of angular momentum conservation on two-dimensional photon tunneling by considering spin Hall effect (SHE) of light. This interesting effect manifests itself as polarization-dependent transverse shifts for a classic wave packet tunneling through a prism-air-prism barrier. For a certain circularly polarized component, the transverse shifts can be modulated by altering the refractive index gradient associated with the two prisms. We find that the SHE in conventional beam refraction can be evidently enhanced via photon tunneling mechanism. The polarization-dependent transverse shift is governed by the total angular momentum conservation law, while the polarization-dependent angular shift is governed by the total linear momentum law. These findings open the possibility for developing new nano-photonic devices and can be extrapolated to other physical systems.

physics.optics↗

arXiv2010

Role of transverse-momentum currents in the optical Magnus effect in free space

We establish a general vector field model to describe the role of transverse-momentum currents in the optical Magnus effect in free space. As an analogy of the mechanical Magnus effect, the circularly polarized wave packet in our model acts as the rotating ball, and its rotation direction depends on the polarization state. Based on this model, we demonstrate the existence of an optical polarization-dependent Magnus effect which is significantly different from the conventional optical Magnus effect in that light-matter interaction is not required. Further, we reveal the relation between transverse-momentum currents and the optical Magnus effect, and find that such a polarization-dependent rotation is unavoidable when the wave packet possesses transverse-momentum currents. The physics underlying this intriguing effect is the combined contributions of transverse spin and orbital currents. We predict that this effect may be observed experimentally even in the propagation direction. These findings provide further evidence for the optical Magnus effect in free space and can be extrapolated to other physical systems.

physics.optics↗

arXiv2010

Integral equation method for the electromagnetic wave propagation in stratified anisotropic dielectric-magnetic materials

We investigate the propagation of electromagnetic waves in stratified anisotropic dielectric-magnetic materials using the integral equation method (IEM). Based on the superposition principle, we use Hertz vector formulations of radiated fields to study the interaction of wave with matter. We derive in a new way the dispersion relation, Snell's law and reflection/transmission coefficients by self-consistent analyses. Moreover, we find two new forms of the generalized extinction theorem. Applying the IEM, we investigate the wave propagation through a slab and disclose the underlying physics which are further verified by numerical simulations. The results lead to a unified framework of the IEM for the propagation of wave incident either from a medium or vacuum in stratified dielectric-magnetic materials.

physics.optics↗

arXiv2010

Three-dimensional Negative-Refractive-Index Metamaterials Based on All-Dielectric Coated Spheres

A type of 3-dimensional optical negative-refractive-index metamaterials composed of all dielectric nanospheres is proposed and demonstrated theoretically. The metamaterials are constructeded by pairing together two kinds of dielectric nanospheres as concentric shells embedded in a host medium. Mie-based extended effective theory shows that the dielectric core and the dielectric shell provide the negative permeability and the negative permittivity, respectively, both due to the strong Mie resonances. Within the coupled resonant frequency region, the negative index of refraction can be achieved.

physics.optics↗

arXiv2009

Spin Hall effect of a light beam in left-handed materials

We establish a general propagation model to describe the spin Hall effect of light beam in left-handed materials (LHMs). A spin-dependent shift of the beam centroid perpendicular to the refractive index gradient for the light beam through an air-LHM interface is demonstrated. For a certain circularly polarized component, whether the transverse shift is positive or negative depends on the magnitude of the refractive index gradient. Very surprisingly, the spin Hall effect in the LHM is unreversed, although the sign of refractive index gradient is reversed. The physics underlying this counterintuitive effect is that the spin angular momentum of photons is unreversed. Further, we reveal that the angular shift in the LHM is reversed due to the negative diffraction. These findings provide alternative evidence for that the linear momentum of photons is reversed, while the spin angular momentum is unreversed in the LHM.

physics.optics↗

arXiv2008

Are photon momenta in left-handed materials reversed?

We develop a semiclassical theory to describe the photon momenta in left-handed materials (LHMs). A single two-level atom is introduced as an "explorer" to probe the momenta of photons. We demonstrate that the linear momentum of the photons reverses its direction in LHMs. However the orbital angular momentum is remains unreversed, although the wave-fronts reversed their screwing fashion. We theoretically predict that the spin angular momentum is also unreversed. The investigation of photon momenta will provide insights into the fundamental properties of LHMs.

physics.optics↗

arXiv2008

Rotational Doppler effect in left-handed materials

We explain the rotational Doppler effect associated with light beams carrying with orbital angular momentum in left-handed materials (LHMs). We demonstrate that the rotational Doppler effect in LHMs is unreversed, which is significantly different from the linear Doppler effect. The physics underlying this intriguing effect is the combined contributions of negative phase velocity and inverse screw of wave-front. In the normal dispersion region, the rotational Doppler effect induces a upstream energy flow but a downstream momentum flow. In the anomalous dispersion region, however, the rotational Doppler effect produces a downstream energy flow but a upstream momentum flow. We theoretically predict that the rotational Doppler effect can induce a transfer of angular momentum of the LHM to orbital angular momentum of the beam.

physics.optics↗