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We systematically study the spin Hall effect of light (SHEL) in the parity-time (PT)-symmetric trilayer structure containing epsilon-near-zero (ENZ) materials, and design a high sensitivity refractive index sensor with an adjustable sensing range. It is revealed that the SHEL shift in the PT-symmetric trilayer structure is clearly enhanced, which is two orders of magnitude larger than that in the conventional sandwich structure containing ENZ materials. The enhancement of the SHEL shift is attributed to the fact that the change of reflection coefficient induced by the quasi-bound states in the continuum (quasi-BIC) in the former structure is smoother than that induced by the bound states in the continuum in the latter structure. It is further found that when the refractive index of the interlayer dielectric in the PT-symmetric structure is fixed, the SHEL shift is significantly enhanced near the quasi-BIC resonance angle determined by the gain-loss coefficient. Meanwhile, the SHEL shift enhanced by excitation of quasi-BIC is very sensitive to the gain-loss coefficient and the refractive index of the interlayer dielectric. Finally, we design a high sensitivity refractive index sensor with an adjustable sensing range based on the quasi-BIC-enhanced SHEL shift. These studies provide a pathway to enhance the SHEL and may open avenues for the application of optical sensors.

The quantized photonic spin Hall effect (PSHE) in the strained graphene-substrate system is predicted under a sub-Tesla external magnetic field, which is two orders of magnitude smaller than required to produce the quantized effect in the conventional graphene-substrate system. It is found that in-plane and transverse spin-dependent splittings in the PSHE, exhibit different quantized behaviors and are closely related to the reflection coefficients. Unlike the quantized PSHE in the conventional graphene-substrate system formed by the splitting of real Landau levels, the quantized PSHE in the strained graphene-substrate system is attributed to the splitting of pseudo-Landau levels caused by the pseudo-magnetic field and the lifting of valley degeneracy of the n ≠ 0 pseudo-Landau levels induced by the sub-Tesla external magnetic field. At the same time, the pseudo-Brewster angles of the system are also quantized with the change of Fermi energy. The sub-Tesla external magnetic field and the PSHE appear as quantized peak values near these angles. The giant quantized PSHE is expected to be used for direct optical measurements of the quantized conductivities and pseudo-Landau levels in the monolayer strained graphene.

Optical analog computing operates on the amplitude, phase, polarization, and frequency distributions of the electromagnetic field through the interaction of light and matter. The differentiation operation is widely used in all-optical image processing technology, such as edge detection. Here, we propose a concise way to observe transparent particles, incorporating the optical differential operation that occurs on a single particle. The particle’s scattering and cross-polarization components combine into our differentiator. We achieve high-contrast optical images of transparent liquid crystal molecules. The visualization of aleurone grains (the structures that store protein particles in plant cells) in maize seed was experimentally demonstrated with a broadband incoherent light source. Avoiding the interference of stains, our designed method provides the possibility to observe protein particles directly in complex biological tissues.

We theoretically investigate the temperature-dependent Goos-Hanchen (GH) shifts in a symmetrical graphene-cladding waveguide (SGCW). The GH shifts in SGCW present a quasi-periodic tendency near the resonance angle with the change of temperature, which can mainly be attributed to the temperature dependence of the guiding layer’s thickness, instead of the graphene intraband conductivity and guiding layer’s refractive index. Importantly, tiny temperature fluctuations can cause significant deviations in GH shifts, and the deviations can be efficiently improved by adjusting the Fermi energy. Therefore, we propose a high-sensitivity temperature sensing scheme based on GH shifts in the SGCW, and the maximum sensitivity can reach up to −2.2 × 105 μ m/ ° C. These researches may open avenues for applications of optical temperature sensors.

We study the Goos-Hanchen (GH) effect in a graphene-substrate system comprehensively by using the transfer matrix method. It is revealed that the magnitude and sign of GH shifts are closely related to the imaginary part of graphene conductivity in the case of the fixed refractive index of substrate, while the Brewster angle position is largely influenced by the real part of conductivity. Further studies show that the position of Brewster angle keeps invariable when the Fermi energy exceeds 0.4 eV, and the magnitude and sign of GH shifts at a certain Brewster angle are changed only by Fermi energy. On the basis of these findings, a scheme to control the positive and negative GH shifts precisely is proposed and demonstrated by instances. We first adjust the refractive index of substrate to control the Brewster angle position under the condition of the Fermi energy exceeding 0.4 eV, and then adjust the Fermi energy to make the GH shift approach target value. Finally, we apply these precise control properties of GH shift to design a refractive index detector with adjustable sensitivity coefficient. These researches may have potential applications in refractive index sensor with high sensitivity and precise measurement of graphene parameters.

We systematically study the lattice-dependent spin Hall effect of light (SHEL) in a Weyl semimetal (WSM) by considering left-handed polarization of the incident beam, and propose a new simple method to sense the lattice spacing precisely. It is revealed that the lattice spacing plays as essential a role as the Weyl points separation in the influences on the SHEL, and the variations of SHEL shifts are closely related to the real part of Hall conductivity. Specifically, the SHEL shifts increase to the peak values first and then decrease gradually with the increase of lattice spacing, and a quantitative relationship between the SHEL and the lattice spacing is established. By simulating weak measurement experiments, the lattice-dependent SHEL shifts are amplified and measured in desirable accuracies. Subsequently, we propose a method of precisely sensing the lattice spacing based on the amplified SHEL shifts. These researches provide theoretical basis for manipulating the SHEL in WSMs, and may open the possibility of fabricating the WSM parameter sensors.

Honey bees make propolis from resins depending on resinous plants available in a particular environment. The aim of this work was to identify the plant origin of Chinese propolis. Through a combina...

We systematically study the role of Weyl cone tilting in the spin Hall effect of light (SHEL) in doped Weyl semimetals (WSMs), and propose a new scheme to determine the type of a WSM and to sense the tilt degree of Weyl cones precisely. It is found that in the case of a small amount of doping, the SHEL in type-I WSMs shows almost no dependence on the tilt degree of Weyl cones, while the SHEL in type-II WSMs is extremely sensitive to variations in the degree of tilt. However, in the case of a large amount of doping, not only the SHEL in type-II WSMs but also the SHEL in type-I WSMs show strong dependences on the tilt degree. These trends are mainly attributed to the variation of the real part of the Hall conductivity with the tilt degree. Remarkably, by using a quantum weak measurement, the tiny SHEL shifts can be amplified and detected to a desirable accuracy. Based on the obviously different tilt-dependent characteristics of amplified SHEL shifts in WSMs, we propose a new scheme to determine the type of a WSM and to sense the tilt degree precisely. By adjusting the doping level, the sensing sensitivity can reach up to 1461.55 µm per degree of tilt. This study may provide an application reference for the fabrication of WSM parameter sensors and other topological photoelectric devices.

We propose a tunable and high-sensitivity temperature-sensing method via weak-value amplification of Goos–Hanchen (GH) shifts in a graphene-coated system. The GH shifts were sensitive to the temperature, which was mainly attributed to the variations in the substrate’s refractive index with the temperature. By introducing the weak-value amplification technique, a temperature-sensing method was produced, in which the sensing sensitivity was two orders of magnitude higher and could be effectively manipulated by adjusting the amplified angle. The sensitivity was improved by regulating the graphene’s Fermi energy. Based on these findings, we obtained a maximum sensitivity of 1 . 3 × 1 0 5 nm/ ∘ C by using the appropriate Fermi energy and amplification angle. These studies expand the practical applications of GH shifts, and provide the potential for developing high-sensitivity temperature sensors based on weak-value amplification.

In this study, Ni3C nanoparticles (NPs) were loaded on LaNiO3 NPs as a co-catalyst during the photocatalytic H2 evolution. The evolution rate of the LaNiO3-3 wt%Ni3C composite (4093.9 μmol g−1 h−1) is about 5 times and 2 times as that of pristine LaNiO3 NPs (819.2 μmol g−1 h−1), and 1 wt% Pt loaded LaNiO3 NPs (1927 μmol g−1 h−1). The effects of co-catalyze with Ni3C on light absorption, electron-hole spatial separation, and surface H2-evolution kinetics are investigated. Loading with Ni3C can enhance the spatial separation of electron-hole pairs, and improve the H2-evolution kinetics. Further investigation shows that surface decomposition of LaNiO3 NPs can only be observed when the Ni3C content is over 3 wt%, caused by the reductive carbon source needed in the loading process. This work indicates that transition metal carbide can be a promising co-catalyst candidate for oxides in photocatalytic applications without concerning corrosion from the reductive carbonaceous precursors in the loading process.

A novel approach is presented for waveguide mode selection by using thin-film spatial filters embedded in multimode waveguides. The waveguide modes are allowed to pass through the spatial filters if and when their mode angles fall within the angle-domain bandwidth of the filters. Consequently the waveguide modes are selectable with varied angle-domain bandwidth of the spatial filters. This approach is relatively simple, cost-effective and features good suppression effect of high-order modes, and is suitable for high-power laser systems.

We studied the electromagnetic scattering from cylindrical cloaks with a quantity of discrete homogeneous layers. The scattering cross sections (SCS) of electromagnetic cloaks designed by different coordinate transformation function are discussed by using a polynomial transform function. The results show that besides the inner boundary, the interfaces between the adjacent discrete anisotropic layers inside the cloak also affect its performance. Through the proper design of the coordinate transformation order, the electromagnetic field distribution insides the cloak can be optimized and the invisible performance of the cloak could be improved with minimization of SCS. These results provide a better way of designing the cloak to achieve low scattering with only a few layers of anisotropic metamaterials.

By using the spatial properties of zero-index gaps in one-dimensional metamaterial photonic crystals, we have designed low-pass spatial filters with small angle-domain bandwidth less than 10 degrees. It is demonstrated by transfer matrix method that the small angle-domain bandwidth and roll-off factor of the spatial filters can be adjusted by changing the structure parameters of the metamaterial photonic crystals. In addition, the spatial filters have absolute polarization-independent properties compared with previous photonic crystal spatial filters. These spatial filters with small angle-domain bandwidth may be applied to the laser science in the future, and decrease the space occupied by the traditional spatial filters.

Recently, constructing nano-twin structure in ZnxCd1-xS nanocrystals have been reported as an efficient way to improve separation of electron/hole pairs during transport in photocatalyst. Most of the nanocrystals with nano-twin structures are synthesized by hydrothermal routine, in which the high pressure inside autoclave may bring potential safety issues. At this work, we present an autoclave free one-pot colloidal synthesis routine to introduce nano-twin structure into Zn0.6Cd0.4S nanoparticles (NPs) using thiourea-metal complex gels. HRTEM analysis, ESR spectra, EIS test, and H2 evolution experiment confirm the formation of nano-twin structures in the Zn0.6Cd0.4S NPs. A series of ZnxCd1-xS NPs (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) are also synthesized by the same method to study the influence of the Zn/Cd composition on the formation of nano-twin structure. The ESR spectra, EIS tests and H2 evolution experiments under visible and ultraviolet light show that nano-twin structure only exist in x = 0.4, 0.6 and 0.8 ZnxCd1-xS NPs, and the concentration of the nano-twin structure is as the sequence as x = 0.6 > x = 0.4 > x = 0.8.

A fuzzy inference method for estimating the heat flux distribution at the metal-mold interface in slab continuous casting is established in this paper. The finite element method is applied to solve the direct heat conduction problem. A set of decentralized fuzzy inference units are established, and the deviations between the calculated and measured temperatures acquired with the thermocouples buried in the mold are taken as the input parameters of fuzzy inference units, and the corresponding inference components are obtained by fuzzy inference. Then the inference components are weighted and synthesized by a weighted integrated approach based on normal distribution function to gain the compensations of the guessed heat flux distribution. Finally, a decentralized fuzzy inference (NDFI) method based on normal distribution weighted approach is formed. Some numerical experiments are performed to study the effects of the number of temperature sensors, different initial guesses of heat flux distribution and measurement errors on the reversion results. Comparisons with both the existing decentralized fuzzy inference (DFI) method and the conjugate gradient method (CGM) are also conducted, and they all show the validity of the inversion method established in this paper.

ZnCdS, a kind of ternary transition metal sulfides, which have tunable absorption in the visible region of solar energy and proper negative conduction band position, is considered as a compatible candidate for effective photocatalytic hydrogen production. Recently, some of the low-cost metal carbides have been demonstrated experimentally to be an excellent substitution of noble metal working as co-catalyst with photocatalysts in H2-evolution process to improve the photocatalytic activity. In this study, Ni3C nanoparticles (NPs) were used as co-catalysts to modify Zn0.3Cd0.7S nanorods during the photocatalytic H2 evolution under visible light irradiation for the first time. The photocatalytic H2 evolution rate of Zn0.3Cd0.7S nanorods under visible light irradiation (517.4 μmolg−1 h−1) is improved for more than six times by loading a suitable amount of Ni3C NPs as co-catalyst (3310.1 μmolg−1 h−1). The structure, composition, and morphology of the Ni3C loaded Zn0.3Cd0.7S nanorods are characterized by XRD, XPS, VSM, SEM, and HRTEM. The effects of co-catalyze with Ni3C on the absorption of visible light, electron-hole separation, and H2-evolution kinetics are investigated. It is believed that loading with Ni3C mainly increases the separation of electron-hole pairs in the photocatalyst, it also reduces the band-gap of the photocatalyst by lowing the CBM position, and improving the kinetics for H2 evolution.

A decentralized fuzzy inference (DFI) method based on the fuzzy theory is proposed in this study for estimating the heat flux distribution of a heated cylinder experiencing conjugate heat transfer. A group of fuzzy inference units (FIUs) are designed. The deviations between the calculated and measured temperature at each measurement point are taken as the input parameters of FIUs, and the corresponding fuzzy inference components corresponding to the measured temperature are obtained by the FIUs. According to the importance of the various measured temperatures, the fuzzy inference components are then weighted and synthesized to gain the compensations of the guessed heat flux distribution. Ultimately, the prediction of the heat flux is accomplished. Numerical tests are performed to study the effect of initial guessed heat flux, measurement point numbers, measurement errors and the coupling of measurement point numbers and measurement errors on the estimated results. The results show that the DFI method can estimate the heat flux availably and possesses a better anti-ill-posed character and higher accuracy than the conjugate gradient method (CGM). The DFI method shows superiority.

Based on the transfer matrix theory, general conditions of polarization-independent transmissions in one-dimensional photonic crystals are derived. It is shown that the polarization-independent transmissions are obtained in photonic crystals consisting of two alternating layers with the same refraction index and optical thickness as well as the mutually reciprocal wave impedance. By using two different photonic crystals satisfying the above relation to constitute the light quantum-well structures, the structures have polarization-independent transmission properties. When a defective layer with wave impedance of 1 is introduced in the photonic crystals, the defective photonic crystals also have the polarization-independent transmission properties. In addition, polarization-independent low-pass spatial filters are achieved based on these photonic crystal structures.

A fuzzy inference method (FIM) for predicting the temperature distribution of the furnace inner surface is proposed in this work. The deviations between the computed and measured temperature at measurement points of furnace wall are taken as input parameters of fuzzy inference units (FIUs), and the corresponding fuzzy inference components of measured information are obtained by the FIUs. According to the importance of the various measured information, the fuzzy inference components then are weighted and synthesized to gain the compensations of the guessed temperature distribution. Finally, the temperature distribution estimation of the furnace inner surface is accomplished. Numerical experiments are performed to study the effects of measurement points number, measurement errors and other factors on the predicted results. Comparisons with the conjugate gradient method (CGM) and the genetic algorithm (GA) are also conducted, and they all show the validity and superiority of the proposed method in the current paper.

The symmetrical confined states are found in photonic quantum-well structures with single-negative materials, in which the photonic barrier is based on the zero-effective-phase gap. The number and frequencies of the symmetrical confined states can be tuned by varying the period number and thicknesses of the well photonic crystal, respectively. Furthermore, the symmetrical confined states of the structures are less sensitive to the incident angle and polarization, compared with previous confined states of photonic quantum-well structures based on the Bragg or zero-average-index gap. The structures open a promising way to fabricate symmetrically tunable and omnidirectional multichannel filters for future dense wavelength division multiplexing applications.

A new application of rugate structures is proposed as low-pass spatial filters for beam smoothing. By using the transfer matrix method to analyze the spatial properties of the bandgap of rugate structures, the low-pass rugate spatial filters with both an almost ideal flat bandpass and a rather steep switching between pass- and stop-bands are designed. The angle-domain bandwidth of the spatial filters can be adjusted by changing the parameters of rugate structures for a given light frequency. The near-field simulations carried out by using the finite-difference time-domain technique confirm the possibility of an efficient light smoothing.

A new application of one-dimensional photonic crystals containing negative-index materials is proposed as low-pass spatial filters. Through optimizing the parameters of defect layer, a series of polarization-independent defect modes in the zero-average-index gap of the photonic crystals are obtained with the increase of the incident angle. Based on these defect modes, polarization-independent low-pass spatial filters are designed. The spatial-frequency bandwidth of the spatial filters can be adjusted by changing the period number of the defective photonic crystal structures. In addition, the effect of the losses of negative-index materials on the spatial filters is considered.

Observation of photonic spin Hall effect (SHE) manifested by spin-dependent splitting of light in a dielectric-based birefringent metasurface is reported experimentally. By designing the metasurface with homogeneous phase retardation but space-variant optical axis directions, we govern the photonic SHE via space-variant Pancharatnam-Berry phase originated from the local polarization manipulation of the metasurface, essentially, the spin-orbit interaction between the light and the metasurface. Modulating the polarization distribution of the incident light and/or the structure geometry of the metasurface, the photonic SHE could be tunable. This type of metasurface offers an effective way to manipulate the spin-polarized photons and a route for spin-controlled nanophotonic applications.

For the needs of engineering talent for country and the characteristics of personnel training for local colleges, with its own teaching conditions of Hunan Institute of Science and Technology, electrical and electronic practice teaching center has made effective reform and exploration in practice of teaching philosophy, teaching content, teaching methods and means and so on. Electrical and electronic practice teaching center constructed a special teaching system, and achieved remarkable results in self-development of teachers and training of students for Hunan Institute of Science and Technology.

This study provides a new inverse approach based on fuzzy inference for solving the problem of estimating heat flux distribution at the metal-mold interface in the continuous casting process. Measured temperatures acquired with the thermocouples buried in the mold are used to obtain corresponding inference results with the fuzzy inference. Then according to the importance of measured information for estimating the heat flux distribution, inference results are weighted to realize estimation of heat flux distribution at the metal-mold interface. Some numerical tests are presented to discuss the validity of the present approach by using different initial guesses of heat flux distribution, the number of measuring points, and measurement errors. In comparison with the conjugate gradient method, it is concluded that the method based on fuzzy inference is of a good anti-ill-posed characteristic.

We propose a new type of wavelength division demultiplexer composed of a photonic crystal waveguide with asymmetric corrugated exit surface. The focus displacement for different symmetric corrugated surfaces is relative to the intensity of the excited surface mode. By systematically investigating the effects of the parameters of the corrugated surface on the focus shift, we demonstrate an on-axis focus by a photonic crystal waveguide with an asymmetric corrugated exit surface at a specific wavelength. The precise equivalences of surface modes at each side of the exit surface are broken. Thus, for the light source with other wavelengths, the emerging beams are off-axis focused at different directions, similar to the function of a wavelength division demultiplexer.