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Dynamical controls on terahertz (THz) wavefronts are crucial for many applications, but available mechanism requests tunable elements with sub-micrometer sizes that are difficult to find in the THz regime. Here, different from the local-tuning mechanism, we propose an alternative approach to construct wavefront-control meta-devices combining specifically designed metasurfaces and globally tuned graphene layers. Coupled-mode-theory (CMT) analyses reveal that graphene serves as a tunable loss to drive the whole meta-device to transit from one functional phase to another passing through an intermediate regime, exhibiting distinct far-field (FF) reflection wavefronts. As a proof of concept, we design/fabricate a graphene meta-device and experimentally demonstrate that it can reflect normally incident THz wave to pre-designed directions with different polarizations under appropriate gating voltages. We finally design a graphene meta-device and numerically demonstrate that it can generate vectorial THz beams with continuously varying polarization distributions upon gating. These findings pave the road to realizing a wide range of THz applications, such as sensing, imaging, and wireless communications.

The optical spin-orbit interaction (SOI) caused by momentum-dependent Pancharatnam–Berry phase (PB) provides new opportunities in the development of spin-optical devices, but the relatively low conversion efficiency limits its application. Here, through rigorous full-wave analyses on it in a parity-time (PT) symmetric system with thickness less than a wavelength, we find that the conversion efficiency of the SOI can be enhanced in both transmission and reflection in a wide range of incidence angles. When the parameters of the PT symmetric system meet the requirement of coherent perfect absorbers-laser mode, the effective anisotropy between the TM and TE components (e.g., a difference of their Fresnel coefficients) within the beam will be amplified dramatically, which results in significantly enhanced conversion efficiency of SOIs (up to 106). These findings offer an effective way to modulate the SOIs with an ultra-thin PT symmetric system, and may exhibit applications in spin-orbit optical devices.

The hierarchical binary CdS/NiO hollow heterogeneous architectures (HHAs) with p-n heterojunction are constructed by a facile microwave-assisted wet chemical process for high-efficient photocatalytic hydrogen evolution reaction (HER) from water. The asdesigned CdS/NiO HHAs are composed of hexagonal n-type CdS nanoparticles with a size in the range of 20–40 nm attaching to cubic p-type NiO hollow microspheres (HMSs) which are aggregates of porous nanoplates with a thickness of about 20 nm. The photocatalytic water splitting over CdS/NiO HHAs is significantly increased under simulated solar irradiation, among which the most active sample of CdS/NiO-3 (the mass ratio of CdS to NiO is 1:3) exhibits the fastest photocatalytic HER rate of 1.77 mmol·g−1·h−1, being 16.2 times than that of pure CdS. The boosted photocatalytic HER could be attributed to the synergistic effect on the proportional p-n heterojunction with special hierarchical hollow and porous morphology, an enhancement of visible light absorption, and an improvement of photoinduced charge separation as well as the photo-stability given by the composite heterojunction. This work shows a viable strategy to design the heterojunction with special morphology for the efficient hydrogen generation by water splitting utilizing solar energy.

The photonic spin Hall effect (SHE), manifesting itself as spin-dependent splitting of light, holds potential applications in precise metrology and spin-based nanophotonic devices. Thus, it’s highly desirable to control this effect at will. However, there lacks an active way for manipulating asymmetric spin splitting, i.e., the asymmetric splitting properties are fixed and cannot be dynamically modulated when the material is fabricated. In this work, we propose a simple and active method for manipulating the asymmetric in-plane spatial and angular shifts by considering a light beam reflected at the glass-air interface embedding with monolayer graphene. We theoretically establish the relationship between the in-plane spin shifts and the conductivity of graphene. We reveal that the in-plane spatial and angular shifts can be significantly adjusted and show obvious asymmetric features by changing the Fermi energy in graphene when the light beam is reflected near the Brewster and critical angles. Interesting, when the incident light is horizontally polarized, the optical shifts are more sensitive to the changes of Fermi energy near the Brewster angle than that near the critical angle. Finally, we propose a potential method that using spin angular shifts to directly detect the tiny variation of Fermi energy.

We find analytically an exact soliton-like solution of cubic-quintic nonlinear Schrodinger equation (CQNLSE) with pure normal fourth-order dispersion (FOD). This exact solitary solution is “fixed-parameter” solitary wave, whose waveform is well described by hyperbolic secant function without oscillating tails. Those characteristics contribute importantly new information on solitons generation compared to the conventional pure-quartic soliton (PQS) in the absence of quintic nonlinearity. The numerical results verify that this exact solitary solution can preserve its shape. The formation of such solitary wave is a result of counterbalance between normal FOD as well as positive Kerr nonlinearity and negative quintic nonlinearity. The stability of such exact solitary wave is discussed as well. Although such exact solitary wave is linearly unstable in the presence of perturbation, our results disclose the role of quintic nonlinearity in the formation of high-energy PQS and its propagation, and also provide a way to control the generation of high-energy PQS laser pulse.

Several works on optical higher-order differential operations have recently attracted attention, particularly in image processing for edge detection. However, the inefficient differential operation leads to barriers to practical applications. Here, we report an anisotropic epsilon-near-zero slab to significantly enhance the transmission efficiency of second-order differentiators and discuss the Berry phase mechanism of this optical calculation process. Through a rigorous full-wave analysis of the process, we find that the conversion efficiency of differential operation depends on the spin-orbit interactions. Our scheme can strengthen the spin-orbit interaction by introducing anisotropy, which significantly enhances the transmission efficiency. We finally give transfer functions to reveal how to improve the efficiency and compare the quadratic coefficient among different systems. This highly efficient differentiation operation may develop significant applications in fast, compatible, and power-efficient ultrathin devices for data processing and biological imaging.

Chemotherapy has been proven to be an efficient strategy for the treatment of prostate cancer (PC). However, the insufficient cellular uptake of drugs is the biggest challenge for PC therapy. Therefore, in order to address the above concern, we developed tumor-targeted hyaluronic acid-silver nanoparticles (HA-Ag NPs), in which hyaluronic acid can specially bind with its receptor CD44 overexpressed on LNCaP cells. HA-Ag NPs have been used to load paclitaxel (PTX) to prepare functionalized silver nanoparticles (HA-Ag-PTX). The average particle size of HA-Ag-PTX was about 70 nm and kept under 120 nm for eight days. androgen-sensitive prostate cancer cells (LNCaP) cells show good uptake of HA-Ag-PTX, and HA-Ag-PTX enters LNCaP cells in a clathrin-mediated energy-dependent manner. HA-Ag-PTX exhibits an excellent pH response release of PTX under the acidic condition, which is beneficial to enhance the distribution of PTX in the tumor microenvironment. HA-Ag-PTX effectively suppresses the migration and proliferation of LNCaP cells probably by arresting the cellular cycle at [Formula: see text]0/[Formula: see text]1 phase and enhancing the production of the reactive oxygen species. It is worth mentioning that HA-Ag-PTX exhibits greater anticancer activity in comparison with free PTX in the LNCaP cell model, indicating that HA-Ag NPs can effectively enhance the anticancer efficacy of PTX. As a whole, these findings suggest that HA-Ag-PTX has promising potential for PC therapy.

The photonic orbital Hall effect (POHE) refers to the vortex-dependent beam shifts, which is generally believed to result from the conversion of intrinsic orbital angular momentum (IOAM) to extrinsic orbital angular momentum (EOAM). However, the physical mechanism of the POHE, such as how the IOAM is converted to the EOAM, remains further elucidation. In this paper, we re-examine the POHE of a vortex beam with additional IOAM illuminating at an optically thin slab by means of vortex mode decomposition. By considering the competition and coupling between the radial and azimuthal vortex harmonics of the abnormal mode in the transmitted beam, it is found that the underlying mechanism of the POHE is in fact a spin-to-orbital angular momentum (OAM) conversion process. And the IOAM carried by the incident beam is directly superimposed on the OAM obtained during the conversion. Our findings not only offer an alternative perspective for understanding the POHE, but also exhibit application potential in orbit–orbit and spin–orbit optical components.

Dynamically controlling terahertz (THz) wavefronts in a designable fashion is highly desired in practice. However, available methods working at microwave frequencies do not work well in the THz regime due to lacking suitable tunable elements with submicrometer sizes. Here, instead of locally controlling individual meta-atoms in a THz metasurface, we show that rotating different layers (each exhibiting a particular phase profile) in a cascaded metadevice at different speeds can dynamically change the effective Jones-matrix property of the whole device, thus enabling extraordinary manipulations on the wavefront and polarization characteristics of a THz beam impinging on the device. After illustrating our strategy based on model calculations, we experimentally demonstrate two proof-of-concept metadevices, each consisting of two carefully designed all-silicon transmissive metasurfaces exhibiting different phase profiles. Rotating two metasurfaces inside the fabricated devices at different speeds, we experimentally demonstrate that the first metadevice can efficiently redirect a normally incident THz beam to scan over a wide solid-angle range, while the second one can dynamically manipulate both the wavefront and polarization of a THz beam. Our results pave the way to achieving dynamic control of THz beams, which is useful in many applications, such as THz radar, and bio- and chemical sensing and imaging.

In general, a spin-polarized light beam cannot couple its spin angular momentum (SAM) with intrinsic orbital angular momentum (IOAM) without spin reversal. Here we find that nonlinear media can give the spin-polarized photon an IOAM, as they travel in the media due to the nonlinear susceptibility along the transmission direction, which does not require spin reversal. To characterize this SAM-to-IOAM conversion process, we establish an evolution ray equation for photons carrying IOAM by reference to the Schrödinger equation. We further reveal the inherent physics of such a phenomenon from a full-wave perspective and find that the vortex generation originates from the nonlinear-induced geometric phase.

We investigate the impact of Raman scattering on pure quartic solitons (PQSs) in an optical fiber with quartic dispersion. An analytical expression of the Raman-induced frequency shift (RIFS) of a PQS is obtained by using the variational approach with the Gaussian function ansatz. We find the RIFS of a PQS is inversely proportional to the sixth power of pulse width, when the fiber is short enough. The RIFS of a PQS is more sensitive to the pulse width, compared with that of a conventional soliton which is inversely proportional to the fourth power of pulse width. The theoretical predictions show good agreement with numerical results. In addition, we also discuss the RIFS of the other three typical pulses with the same peak power and pulse width as the PQS. These results provide a thorough understanding of the role of higher-order nonlinear effects on the propagation dynamics of PQSs.

Supplementary material

We revisit the photonic spin-Hall effect upon reflection/refraction and find the reflected/refracted beam contains a spin-maintained component and a spin-flip one acquiring different geometric Berry phases and distinct spin-Hall shifts.

The fruitful progress toward light manipulation in reflective (R) or transmissive (T) geometry (half-space) has facilitated strong aspiration to achieving full-space electromagnetic wave control in both R and T channels. Although it promises large-capacity and integrated functionality, yet imposes prohibitive difficulty and big challenging for extreme wave control (direction of arrival in full space) via an ultrathin flat device. As of today, very limited demonstrations were reported for single-band and linear-polarization operation, significantly limiting the exploitable degree of freedoms (DoFs) for real-world applications. Herein, we report for the first time a triple-layer wavelength-space multitasking scheme for wide-angle and large-capacity detection. Two anisotropic sub-meta-atoms are engineered with high quality factor and simultaneous in-plane and out-of-plane symmetry breaking, facilitating four R and two T spin-conversion channels with high efficiency and insulation. The chirality-assisted Fano effect gives rise to the wide-angle operation and boosted channels. Above features and released DoF would be extraordinary beneficial for large-capability and angle-engineered advanced device. Two proof-of-concept metadevices, i.e., large-scanning kaleidoscopic-beam generator and a wide-angle large-capacity reverser for multi-target tracking, are devised to verify the significance. Numerical and experimental results have approved predesigned advanced functions at six channels with measured efficiency over 75%. Our findings in multi-DoF multitasking of metasurfaces could stimulate great interest in radar applications with versatile beam generation and multi-channel integration.

Recently, Pancharatnam–Berry (PB) metasurfaces have exhibited powerful capabilities to control spin-polarized light. However, the adopted abrupt PB phase, introduced by simply rotating the basic elements, is spin-locked with opposite signs for different spin excitations, greatly limiting their practical applications. Here, we introduce a high-efficiency and broadband spin-unlocked metasurface with two mechanisms of a resonance phase and a geometric phase perfectly combined together. The design strategy is quite simple just through changing one geometric parameter rather than multi parameter optimization. As a proof of concept, the anomalous photonic spin Hall effect based on the spin-unlocked metasurface is demonstrated first, showing high experimental efficiency (over 80%) in a broad frequency range (11.3–16.6 GHz). Furthermore, another spin-unlocked metasurface is built to demonstrate the completely independent wavefront manipulations, i.e., the focusing effect and anomalous reflection. These findings significantly expand the electromagnetic control ability of a metasurface.

A light beam reflected and refracted at a sharp interface can acquire a momentum-dependent Pancharatnam–Berry (PB) phase, which produces a topological phase transition from one kind of spin–orbit interaction (e.g., spin-controlled vortex generation) to another (e.g., photonic spin-Hall effect). However, this process is extremely inefficient and difficult to observe directly in experiments, which also hinders its applications. Here, we propose to enhance significantly the topological phase transitions by c-cut uniaxial crystals. We first give a full-wave theory to describe the spin–orbit interactions of a beam passing through a c-cut uniaxial crystal and experimentally observe the topological phase transition process of the transmitted beam when the angle between the beam propagation direction and the optical axis direction changes. It is found that the efficiency of the spin–orbit interactions caused by the momentum-dependent PB phase can be increased as high as 50%, which is much larger than that at isotropic sharp interfaces. Our findings provide an alternative approach for manipulating the spin and orbital angular momenta of light and exhibit potential applications in the future spin–orbit photonic components.

Photonic spin Hall effect (SHE) manifests itself as spin-dependent shift or splitting of a light beam, which is derived from spin–orbit interactions, and can be realized by breaking the rotation symmetry of light–matter interaction systems. Here, we demonstrate the observation of a photonic SHE by breaking the rotation symmetry of the optical field, while keeping the rotation symmetry of the inhomogeneous waveplate. The inhomogeneous waveplate constructed by dielectric nanostructures, introduces a spin-dependent Pancharatnam–Berry phase to the two spin components of the input beam, i.e., the left- and right-circular polarization components acquire exactly opposite vortex phases. During beam propagation, they experience opposite azimuthal rotations, and induce a four-lobe spin-dependent splitting in the azimuthal direction. In addition, the spin-dependent splitting becomes more evident upon beam propagation, and can be enhanced by increasing the topological orders of the nanostructures. For comparison, we also examine that no spin-dependent splitting can be observed when keeping the rotation symmetry of the incident optical field.

Photonic spin Hall effect (SHE) can be an effective sensor for determining the refractive index (RI) variation of a sensing medium. How to further improve its sensitivity is a very interesting and important issue. In this paper, we theoretically propose a weak measurement method for enhancing the sensitivity of the photonic SHE-based RI sensor by reducing the influence of the in-plane wavevector. Of particular interest, our results indicate that the sensitivity of the presented configuration reaches about 3.16 × 10-7 RIU/μm which shows nearly two orders of magnitude improvement compared with the conventional one. Remarkably, this method can be applied for wide range of RI variation of the sensing medium while keeping the high sensitivity.

Optical beam shifts, which mainly refer to the Goos–Hänchen shift and spin-Hall shift, widely exist in basic optical processes such as interface reflection and refraction. They are very sensitive to changes in the parameters of the materials that constitute the interface and therefore show great potential for applications in precision metrology and sensing. The interaction between light and two-dimensional (2D) atomic crystals is very weak, and beam shifts provide an alternative approach to explore and characterize 2D atomic crystals. In this paper, we first present a full-wave theory of beam shifts and introduce the experimental measurement of beam displacements with quantum weak measurement technology, and then review their applications in characterizing 2D atomic crystals, such as determining the layer number and measuring the optical conductivity of few-layer graphene. Finally, we discuss the beam displacements in twisted bilayer 2D atomic crystals and 2D atomic crystals under applied electric or magnetic fields.

Vortex beams have been extensively realized using different approaches. Typically, the efficiency and bandwidth of a vortex beam are limited by impure copolarized components and the intrinsic dispersion of passive resonant structures. Here, we propose a strategy to generate wideband vortex beams by using a Pancharatnam–Berry metasurface in which two orthogonal reflections exhibit a broadband out-of-phase difference. To achieve this, a broadband strategy based on multimode operation and dispersion engineering methods was established. A dual-layer meta-atom is proposed; each layer comprises of five metallic dipoles, and the geometrical parameters are carefully adjusted to tune the resonant frequencies. Because the dipole orientations in each layer are orthogonal, the reflection responses under the two orthogonal polarizations can be independently engineered. Both numerical and experimental results indicate that our method not only enables a high-efficiency spiral beam conversion over a broad range of 6.95–18 GHz (>82%) but also causes a polarization-insensitive effect; thus, it can be adapted for any linear or circular polarization.

Diffusive scatterings of electromagnetic (EM) waves by a thin screen are important in many applications, but available approaches cannot ensure uniform angular distributions of low-intensity scatterings without time-consuming optimizations. Here, we propose a robust and deterministic approach to design metasurfaces to achieve polarization-independent diffusive scatterings of EM waves within an ultrabroad frequency band and for wide-range of incident angles. Our key idea is to use high-efficiency Pancharatnam–Berry meta-atoms to form subarrays exhibiting focusing reflection-phase profiles, that can guarantee nearly uniform diffusive scatterings for arbitrarily polarized EM waves. As an illustration, we design and fabricate two metasurfaces and experimentally characterize their wave-diffusion properties in C, X, and Ku bands. Theoretical, numerical and experimental results demonstrate that our approach can diffuse the incident energy much more uniformly than available approaches based on the uniform-phase s...

In this work, we propose a method for generating double-ring-shaped cylindrical vector beams by modulating Pancharatnam–Berry phase (PBP). The theoretical analysis shows that the output field can be expressed as the coherent superposition of two circularly polarized Laguerre–Gaussian components with opposite polarization handness and opposite helical index when a linearly polarized fundamental Gaussian beam inputs the metasurface designed based on PBP. Such a superposition of Laguerre–Gaussian modes forms a double-ring-shaped cylindrical vector beam. Additionally, the local polarization orientation can be manipulated by changing the polarization angle of the input field. Our experimental results agree well with the theoretical expectation. We believe that PBP provides an extra choice to manipulate the phase and polarization of optical field.

We theoretically propose the realization of a three-dimensional (3D) spin Hall effect (SHE) of light by tightly focusing a linearly polarized light. Owing to the spin-orbital interaction in focusing, the left and right circularly polarized components of light are partly converted into each other, acquiring opposite vortex phases. As the superposition of the vortex and the initial vortex-free light, the two polarized components exhibit spiral intensity patterns which rotate oppositely around the propagation axis. Consequently, the two spin components are distributed alternatively in both the azimuthal and the longitudinal directions, leading to a 3D array of split spin components, and the transverse intensity is also spit asynchronously. Moreover, that array is rotatable by the incident polarization, and the longitudinal spacing in the array can be controlled by the numerical aperture of the lens. The 3D SHE of light finds an additional degree of freedom available to control the spin state of the photon, which may be valuable in optical manipulation and quantum information.

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 $(0.993\pm0.005)\sigma_0$ is detected, and a high measuring resolution with $1.5\times10^{-8}\Omega^{-1}$ 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., Comment: 5 pages, 5 figures

In this paper, the propagation properties of hollow Gaussian beams (HGBs) are discussed in detail when they are off-waist incident in strongly nonlocal media. A set of mathematic expressions are given to describe the evolutions of the beam intensity, the beam width, and the real beam radius. Numerical simulations are carried out to illustrate these propagation properties depended on the off-waist incidence. It is found that a HGB always periodically transforms its transverse patterns during propagation. Accordingly, the beam width and the real beam radius are also periodic during propagation. Keywords: Hollow Gaussian beam, Strongly nonlocal media, Propagation property, Off-waist incident case

In high-power laser systems for inertial confinement fusion, hot images may be intense enough to damage expensive optical components. Basing on split-step fast-Fourier-transform algorithm, the intensity and location of hot images of a spectrally dispersed sinusoidal phase modulated laser beam is numerically investigated. It is found that, the time-average intensity of hot image firstly decreases monotonically with the modulation depth and eventually reaches a certain minimum, then increases slowly and reaches a saturated value; in addition, with the modulation frequency and the grating dispersion coefficient increasing, the time-average intensity of hot image decreases generally; while the location of hot image always does not change. Finally, the influence of the distance from the obscuration to the nonlinear optical element on the suppression effect of spectral dispersion of sinusoidal phase modulated light on formation of hot images is discussed. The result is helpful to appropriately choose parameters of the spectrally dispersed sinusoidal phase modulated light to minimize the threat of optical damage of hot image and improve the performance of high-power laser system.