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The discovery of Photonic spin Hall effect (PSHE) on surface plasmon polaritons (SPPs) is an important progress in photonics. In this paper, a method of realizing multi-channel PSHE in two-dimensional metal-air-metal waveguide is proposed. By modulating the phase difference $$\phi$$ ϕ and polar angle $$\theta$$ θ of the dipole source, the SPP can propagate along a specific channel. We further prove that PSHE results from the component wave interference theory. We believe that our findings will rich the application of SPPs in optical devices.

The main function of the curved superlens is to magnify or minify the image of the pattern cut onto the mask in a photolithograph device. It is found theoretically, in this paper, that the magnifying or minifying function deals with two important properties: one is the magnifying (or minifying) effect and the other is the image quality. The magnifying (or minifying) effect of a specific superlens device can be expressed by a linear function and the image quality can be guaranteed by a quadratic function. The ways to obtain the two functions have been demonstrated in this paper.

The finding of Photon Hall effect (PHE) on metal surface is an important progress in photonics, but it will be more practical if PHE can be realized in line-type waveguide. In this paper, we suggested a way to realize PHE in two-dimensional photonic crystal (PC) waveguide. Numerical simulation results show that the propagating direction and strength of light in the PC waveguide can be controlled by the polarization state of incident light. Different from the PHE on metal surface, the PHE in PC waveguide can be driven not only by circularly polarized light, but also by linearly polarized light. The PHE in PC waveguide can be attributed to the interference of the two component waves excited by the incident light.

A general method is proposed to describe the energy levels of the interface states in one-dimensional photonic crystal (PC) heterojunction [Formula: see text] containing dispersive or non-dispersion materials. We found that the finite energy levels of the interface states for the finite configuration can be described totally by the dispersion relation of the PC with a periodic unit [Formula: see text]. It is further found that this method is also applicable for the case of defect modes. We believe our method can be used to guide the practical application.

The generalized scattering coefficient (GSC) method is pedagogically derived and employed to study the scattering of plane waves in homogeneous and inhomogeneous layered structures. The numerical stabilities and accuracies of this method and other commonly used numerical methods are discussed and compared. For homogeneous layered structures, concise scattering formulas with clear physical interpretations and strong numerical stability are obtained by introducing the GSCs. For inhomogeneous layered structures, three numerical methods are employed: the staircase approximation method, the power series expansion method, and the differential equation based on the GSCs. We investigate the accuracies and convergence behaviors of these methods by comparing their predictions to the exact results. The conclusions are as follows. The staircase approximation method has a slow convergence in spite of its simple and intuitive implementation, and a fine stratification within the inhomogeneous layer is required for obtai...

The influence of lubrication on profile and flatness control during asymmetry self-compensating work roll (ASR) hot strip rolling process is studied in order to meet the requirement of schedule-free rolling (SFR) campaigns for non-oriented electrical steel production with identical strip width. The effects of lubrication on rolling force, surface topography, and work roll wear are analyzed through experimental data. A work roll wear model for a wide non-oriented electrical steel production considered lubrication during the hot rolling process is built, which can accurately reflect the work roll wear during the hot rolling process with lubrication. A 3D finite element model for roll stack considering lubrication is built. The effects of shifting strategy on ASR work roll wear contour, loaded roll gap crown, and edge drop are analyzed based on the models. The optimal shifting rhythm is 1, and the optimal shifting step is 2 ~ 3 mm. By combining the ASR technology with lubrication, the life of work rolls expands from 70 to 100 ~ 150 by different shifting step, the loaded roll gap crown can be efficiently controlled by bending force and the edge drop control ability can be improved efficiently within an entire rolling campaign.

A novel line-type optical one-way transmission structure is proposed, which consists of a helical subwavelength metal slit. The simulation results obtained from finite-difference time-domain method show that this structure has excellent one-way transmission properties. When a polarized light propagates forward through the structure, its polarization direction will be rotated 90 degree. The backward propagation is blocked.This helical slit can also be a one-way unit of a plane-type one-way transmission structure, in which the setting angle plays an important role in determination of the transmission properties of the one-way plane via the strong coupling effect between the waves in adjacent slits.

The continuous photon Hall effect excited in a surface plasmon polariton system is proposed and realized theoretically, in which the parallel incident light illuminates the small ball nearing the surface. The scattering direction can be continually modulated in the large range of almost 180 degree by the elliptical polarization state of the incident light. The physical reason is displayed intuitively by the component waves interference principle.

The zero-refraction property of a metal film can be used to image so that the metal film behaves as a superlens. Experimentally, the metal superlens is sandwiched between the photosensitivity resist (PR) and the dielectric spacer in the photolithograph device to produce images. In this paper, the imaging conditions of the metal superlens, or the parameters of the device containing the superlens are investigated in detail. It is found that the energy zero-refraction effect is the intrinsic property of the metal superlens. The permittivities of the dielectrics at the two sides of the superlens will influence the imaging quality. The rule is drawn for obtaining best images: the two dielectrics should have the same permittivities, so-called symmetry case, and the real part of the permittivity of the metal superlens plus the dielectric permittivity is just equal to 1, i.e. ϵ ( dielectric ) + ϵ r ( superlens ) = 1 .

In this paper, Dirac point method is used to study the interface state of one-dimensional photonic crystal heterojunction [Formula: see text] containing dispersive materials GaAs. We found that the energy levels of the interface states satisfy a simple sinusoidal function. We investigate the variation of the energy levels of the interface states with the incident angle, it is found that these interface states move toward high-frequency with the increase of the incident angle. At the same time, it is found that there is an extra localized band and it is further proved that the extra band corresponds to the defect band, and the energy levels of the defect band possess the same behavior with those of interface states.

A very facile way to obtain multiple interface modes in a one-dimensional photonic crystal heterostructure is proposed in this Letter. We found that the interface modes can be generated by introducing the interfaces, and the number of interface modes equals the number of introduced interfaces. All these interface modes originating from a different geometric Zak phase can create two band branches governed by the two different interfaces. We further find that the two band branches can be renormalized into one band branch with discrete energy levels in the form of sinusoidal function. We believe that these findings can be used to provide direct guidance for practical application and can also make the estimation of practical samples more convenient.

In this study, an analytical solution is proposed to solve the general problems of three-wave mixing with pump depletion. The so-called quasi-phase-matching (QPM) for χ ( 2 ) nonlinearities, including sum frequency generation (SFG), second harmonic generation (SHG) and difference frequency generation (DFG), is amended when the depletion of the pumping light power is considered. The optimum domain width and the corresponding conversion efficiency are discussed. The optimum domain widths deviate from the coherence length l c = π / Δ k , but the deviation is so small that it can be ignored according to the actual situation. The applicable scope of undepleted pump approximation (UPA) is estimated by a proposed relative tolerance. Analysis indicates that the relative tolerance showing the difference of conversion efficiency between the UPA and the exact solution is solely determined by the conversion efficiency. Based on the relative tolerance curves for SFG, SHG, and DFG, two models are developed: one can be used to describe the SFG and SHG processes, whereas the other can be used for the DFG process. These findings can be used to provide direct guidance for practical application, and can also make the estimation of practical samples more convenient.

A tunable optical unidirectional device or optical isolator composed of a metal subwavelength grating covered with magneto-optical rotation medium is proposed. The results of a simulation show that the difference of transmissivity in opposite directions varies from 0 to 83% with an external magnetic field at room temperature. The largest field needed to control transmissivity is only 1.1 T, so the working conditions can be easily achieved. A theoretical method to calculate transmissivity is presented and the unique transmission characteristics of this new device are explained satisfactorily.

In this paper, the spalling causes of backup rolls in a roughing mill of a hot strip rolling mill were investigated. The roughing mill withstood extreme service conditions with long service cycles for backup and work rolls, a large variety of the same width rolling campaigns, severe and non-uniform wear contours of backup and work rolls. Analysis of cyclic stress applied on backup rolls indicated that contact stress played a dominant role in rolling contact fatigue which led to spalling on the backup roll surface. A 3D finite element model of roll system was established and contact stresses between rolls in whole service periods of backup and work rolls were calculated. The simulation results showed that roll wear had significant impact on contact stress distribution. In particular, the severe and non-uniform U-typed wear contours of work rolls led to produce huge contact stress peak in two sides of the rolls, where existed large cracks by eddy current inspection of post-service backup rolls. Backup rolls stood thousands of times stress cycle in a service period, they were liable to fatigue damage in these areas. A new backup roll contour was developed to improve contact stress distribution and no spalling accidents were happened any longer after applied to the roughing mill.

The mechanism of the unidirectional transmission in metal subwavelength gratings with different surfaces is investigated theoretically. This kind of unidirectional transmission belongs to the extraordinary optical transmission assisted by the surface plasmon polariton (SPP). The SPP wave comes through the multi-reflection process and finally transforms into the transmission wave. The difference of amplitude transmissivities and reflectivities at different surfaces in opposite incident directions results in the unidirectional transmission. A division method is proposed to calculate the parameters of subwavelength gratings with asymmetric surfaces.

This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers.

The nanostructure of amorphous carbon thin film is described in terms of a disordered conductive sp2 phase embedded in an electrically insulating sp3 matrix. The conductive sp2 phase is dominated by Drude type free-carries response, and the carrier conductive between sp2 clusters is hopping. The two conductivities are in a serial configuration under a percolation approximation. In view of this, we extend Shimakawa’s model for compact nanoparticles [14] to amorphous carbon thin films in order to provide understanding on its terahertz (THz) optical complex permittivity. Furthermore, the contribution of phonons for THz optical complex permittivity is included in the scope of Debye theorem phenomenologically. Considering the condition of ω ω TO and the narrow frequency range, we interpret the complex phonon permittivity experimentally as e phonon = A ω e i θ for amorphous carbon. Thus, the real and imaginary permittivity can be simultaneously explained by the above considerations. It is the first qualified analysis on the THz optical properties of amorphous carbon thin films experimentally.

We investigate light transport in metal slits filled with a one-dimensional periodic stack of low- and high-index dielectric media. We have analytically extracted an exact independent-mode model where each transverse eigenmode is subject to its own Bragg scattering and dispersion modulation. The analytical model allows for easy analysis of the complex band structures calculated by means of the finite-difference time-domain method, where the physical origin of each band can be identified and assigned to a certain eigenmode of a metal slit. The analytical model is also very efficient and convenient to analyze the optical transmission spectra for these metal slits. The origin of all subtle spectral features can be discerned from the band diagram analysis of the relevant independent eigenmodes. A comparative study shows that the simple analytical independent-mode theory is powerful in handling the intrinsic light transport problems for periodically modulated metal slits and analyzing their complicated spectru...

Economic lot and scheduling problem is one of the focuses in the international engineering field. Aiming at several kinds of products and sets of production lines, this paper introduces a production model, which is based on the principles of artificial intelligence and introduces random factors as time changes, such as market demand and production line equipment. Besides, this paper puts forward a dynamic heuristic search production schedule method, and the simulation results show that the effectiveness and predictability of this method.

We introduce a method to obtain and describe the multiple defect modes in the multiple photonic quantum-well structure [(AB)mC]n(AB)m. It is found that the relationship between structural parameters and defect modes can be obtained by analytically solving the dispersion relationship for the photonic crystal with its periodic unit [(AB)mC], and a laconic and unifying expression can be used to describe the energy levels of both the interface modes and defect modes. The internal mechanism to determine the related parameters is revealed. We believe that these findings can be used to provide direct guidance for practical application.

We investigate one-dimensional nonlinear photonic crystals consisting of ferroelectric domains with the modulated polarization directions. Significant enhancement of second harmonic generation (SHG) is observed from numerical simulations when the frequency of fundamental wave is aimed at the photonic band edge. We devise the model structure with optimal configuration of the polarization directions of the ferroelectric domains in terms of simulated annealing algorithm. The conversion efficiencies of the ‘forward’ and ‘backward’ SHGs can be engineered.

We report an intense (∼10mW) and ultra-broadband (∼150 THz) THz to infrared (IR) source with a Gaussian wavefront, emitted from nano-pore-structured metallic thin films with femtosecond laser pulse excitation. The underlying mechanism has been proposed as thermal radiation. In addition, an intense coherent THz signal was generated through the optical rectification process simultaneously with the strong thermal signal. This unique feature opens up new avenues in biomedical research.

One kind of optical unidirectional transmission structures is proposed which is composed of a metal subwavelength slit dressed by one or two gratings. Simulation results show that the gratings with different geometry parameters can play different roles. One role is the convergence effect and the other is shield effect. Each effect can independently cause the unidirectional transmission with special properties. These two effects are explained in view of optical reciprocal theorem. Combination of the two effects results in excellent unidirectional transmission properties.

Terahertz (THz) spectroscopic sensing and imaging has identified its potentials in a number of areas such as standoff security screening at portals, explosive detection at battle fields, bio-medical research and so on. With these needs, the development of an intense and broadband THz source has been a focus of THz research. In this work, we report an intense (~10 mW) and ultra-broadband (~150 THz) THz to infrared (IR) source with a Gaussian wavefront, emitted from nano-pore-structured metallic thin films with femtosecond laser pulse excitation. The underlying mechanism has been proposed as thermal radiation. In addition, an intense coherent THz signal was generated through the optical rectification process simultaneously with the strong thermal signal. This unique feature opens up new avenues in biomedical research.

We calculate the omnidirectional dispersion spectrum for one-dimensional (1D) photonic crystals (PCs) inserting multiple photonic quantum-wells (PQWs) with the use of the plane-wave expansion method in combination with a supercell technique. We find that the localized defect modes significantly depend on the number of the PQWs and the configuration. This may provide a new way to engineer the dispersions of the composite PCs to meet the requirements of optical or microwave devices.

The parametric amplification (PA) and second harmonic generation (SHG) from quasi-one-dimensional aperiodic optical superlattices (AOSs) are investigated in the cases of large, intermediate, and small signals of the pumping light wave. The optimal design of the AOSs is carried out with the use of the simulated annealing (SA) method. The numerical simulations show that the constructed AOSs can achieve multiple wavelength PA (or SHG) with identical amplification (or identical conversion efficiency) at the pre-assigned wavelengths. The variations of the normalized intensities of the PA signal (or the pumping fundamental wave (PFW)) for the PA process with the distance of propagation of the light wave from the interface of the AOSs at the pre-assigned wavelengths exhibit monotonically increasing (or decreasing) behavior. So do the variations of the normalized intensities of the second harmonic wave (SHW) (or the fundamental wave (FW)) for the SHG. This strongly supports the fact that the contribution of each individual unit domain in the constructed samples to the PA (or SHG) is constructive accumulation, favorable for the PA (or SHG) process. The saturation phenomenon of the PA (or SHG) signal is observed.

We investigate the evolution of the band gap in one-dimensional (1D) photonic crystals (PC) with the gradual modifications of structural configurations from photonic quantum wells to PC heterostructures. The transmissive spectra are calculated with the use of scattering matrix method. We find that the transmissive spectra and confined states strongly depend on the structural configurations of samples.

We have studied second-harmonic generation (SHG) from quasi-one-dimensional aperiodic optical superlattices (AOSs) of finite lateral width by inverting poled ferroelectric domains. The search for optimal AOS structures corresponds with solving a difficult inverse source problem. We describe the design principle in real-space representation and undertake model designs. The numerical simulations show that the constructed AOSs can implement multiple-wavelength SHG with identical effective nonlinear coefficients at the pre-assigned wavelengths of the incident light. We investigate the effects of mode–mode coupling and the lateral width of the superlattice on the SHG for two cases: incident light beams of plane-wave and Gaussian profiles. When the number of modes increases, the effective nonlinear coefficient decreases in an oscillatory fashion at the beginning and then tends to a constant. For an incident plane-wave beam, the dependence of the effective nonlinear coefficient on the width of the sample is quite weak, while for an incident Gaussian beam this dependence exhibits a rapid decrease at the beginning and then tends to a constant. We display the variation in the effective nonlinear coefficients with the distance of propagation of the optical wave from where the incident light beam impinges on the sample surface and find that this variation exhibits monotonically increasing behaviour. This clearly infers that the contribution of every block to the optical SHG process takes the form of constructive addition. It is expected that this new design method may provide an effective and useful technique for constructing nonlinear optical material to match various practical applications.

We investigate the properties of guide modes localized at the interfaces of photonic crystal (PC) heterostructures which are composed of two semi-infinite two-dimensional PCs consisting of non-circular air cylinders with different rotating angles embedded in a homogeneous host dielectric. Photonic band gap structures are calculated with the use of the plane-wave expansion method in combination with a supercell technique. We consider various configurations, for instance, rectangular (square) lattice–rectangular (square) air cylinders, and different rotating angles of the cylinders in the lattices on either side of the interface of a heterostructure. We find that the absolute gap width and the number of guide modes strongly depend on geometric and physical parameters of the heterostructures. It is anticipated that the guide modes in such heterostructures can be engineered by adjusting parameters.

We first investigate the band gap structures of two-dimensional magnetic photonic crystals (MPC) composed of rectangular (square) magnetic cylinders embedded in a host dielectric material in the rectangular (square) lattice, and we then study guide modes at interface of MPC heterostructures (MPCHs) by use of plane wave expansion method in combination with supercell technique. We find that both the mirror-symmetric MPCHs and the mixed-type MPCHs composed of square cylinders in a square lattice can produce the TM guide modes even without any lattice distortions. This feature is quite different from that of the non-magnetic PC heterostructures, in which the occurrence of the guide modes requires the relatively longitudinal gliding or transverse displacement of lattices. It may provide a new way to generate guide modes and apply to the device of light wave guides.

Ultra-thin optical coating comprising nanometer-thick silicon absorbing films on iron substrates can display strong optical interference effects. A resonance peak of longitudinal Kerr rotation with the silicon thickness of was found at the wavelength of 660 nm. The optical properties of silicon thin films were well controlled by the sputtering power. Non-iridescence color exhibition and Kerr rotation enhancement can be manipulated and encoded individually.

Second harmonic generation (SHG) in a two-dimensional (2D) nonlinear photonic crystal (NPC) with finite width along [Formula: see text]-direction that is embedded in air is investigated, without adopting the traditional approximations such as a plane-wave approximation (PWA) and slowly varying amplitude approximation (SVAA). The so-called quasi-phase-matching (QPM) and the corresponding SHG conversion efficiency can be modulated significantly by the field of fundamental wave (FW). It is assumed that the incident light, along [Formula: see text]-direction, is normally launched upon the surface of the sample, and QPM for different directions is investigated. It is found that the QPM shows significant differences, compared with the traditional QPM along the two different directions: in the direction of finite width of the sample, the peak value of SHG conversion efficiency is deviated from the traditional case and it gets to its peak values when the transmittance resonance occurs. However, in the other direction, the deviation from the traditional QPM arises from the field modulation of the second harmonic wave (SHW) and in this direction, it is investigated that the full width at half maximum of QPM is much wider than that in the direction of finite width of the sample. These results can be used to provide a theoretical guidance for achieving QPM SHG.

By the multiple reflections and transmissions in a dielectric on a ferromagnetic metal, color and Kerr rotation correlate with each other. It is revealed that the real refractive index of dielectric plays a major role on the variations of color and Kerr signal, while the absorbing term adjusts the intensive color exhibition and Kerr enhancement at much thinner dielectric thickness. The intensive Kerr signal variation is always accompanied by the color transition with the dielectric thickness changing. Experimental results observed in silicon(or silica)/iron samples are well consistent with calculations. Nanometer dielectric optical coating can not only enhance Kerr effect but also endow magnetic surface with chromatics, which has promising potential applications in anti-fake brands, colorful decorations, camouflages, and even bionics.

The rolling force prediction model for electrical steel in hot rolling was established. A 3D elastic-plastic finite element model of roll and strip was established by MSC. Marc software package. The influence of strip thickness, rolling temperature, strip width, friction coefficient, reduction and rolling speed on rolling force was attained by simulation. The rolling force prediction model for electrical steel in hot rolling was established based on FEA and BP neural network. The model with high accuracy and calculation efficiency can be used to guide the production.

Second harmonic generation (SHG) from the aperiodic optical superlattice (AOS) in considering the pump depletion is investigated. It is found the domain configuration designed in undepleted pump approximation (UPA) can also be used to achieve multiple wavelength SHGs with high enough conversion efficiency for an exact solution. The applicable scope of UPA was estimated by a relative tolerance based on the related SHG conversion efficiency calculated in UPA and an exact solution. Results reveal that the relative tolerance is solely determined by the conversion efficiency, and unrelated to the sample configuration, pump intensity, incidental wavelength and nonlinear media. A model to evaluate an exact solution is proposed, and it is suggested that the SHG conversion efficiency can be easily assessed by the developed model. These results can be used to provide direct guidance for practical application, and can also make the estimation of practical samples more convenient.

The integration effects on flatness control during hot rolling process is studied for meeting the requirement of schedule-free rolling (SFR) campaigns of non-oriented electrical steel strips with identical width. A 3D finite element model for elastic deformation of rolls is built by ANSYS. The integration effects of lubrication, asymmetry self-compensating work rolls (ASR), and varying contact back-up roll (VCR) contours on flatness control are comparatively analyzed. An improved strip profile, flatness, and rolling stability are achieved by combining these technologies. The total rolling coil number is increased from 70 to 100 within a rolling campaign. The lateral stiffness of roll gap is increased by 10.3 and 12.75% in the early and later rolling stage, respectively.

The one-way devices in optical circuits are the key components just as the diodes in electric circuits, which allow the light going in only one direction. A novel one-way transmission structure is proposed which is a curved waveguide containing a confined photonic crystal. When the waveguide is made of perfect electric conductor, the exact calculation results demonstrate that the device shows excellent one-way properties. The forward transmissivity approaches 100% and the largest transmission ratio exceeds 100.92N, where N is the cell number of the photonic crystal in the structure. When the waveguide is made of real metal, the device also presents excellent one-way transmission properties, which can be confirmed by an approximate calculation as well as by the simulation. In working region, the lowest forward tranmissivity is about 30% and the largest one exceeds 70%. The highest transmission ratio exceeds 104.

We present a general solution of second harmonic generation (SHG) without adopting the slowly varying amplitude approximation when light is incident obliquely upon one-dimensional(1D) inhomogeneous systems. The one-dimensional nonlinear photonic crystals consisting of ferroelectric domains with the modulated polarization direction are investigated. We find that the wavelength which is located at the photonic band edge shifts to the short-wavelength with the increasing angle of incidence. The SHG is enhanced significantly when the frequencies of fundamental wave aim at the photonic band edges and the special arrangement of the polarization directions of the ferroelectric domains is satisfied.

We found that a single negative material has a character of zero-refraction in near field, and point out that the mechanism of a metal superlens to image with the resolution exceeding the diffraction limitation is different from that of a perfect lens made of a double negative material. The principle of metal superlens is disclosed. Our numerical results based on the zero-refraction character coincide with the experimental results well. This work brings new understanding about the single negative materials and will lead the applications of metal superlens in right way., 11 pages, 4 figures

A simple optical structure, termed a pillar-slit structure, is proposed to enhance the contrast ratio of the weak optical signal. The structure consists of a metal slit surrounded by two metal pillars and can be directly incorporated onto optical sensors. The waves excited on the incident surface are modulated by the pillars and then scattered by the slit entrance so as to generate the in-slit surface plasmon polaritons passing through the slit. The transmission power is modified by the surface wave intensity. This structure is capable of suppressing background and enhancing signal light simultaneously. A calculated illustration by the numerical simulation method shows that an increase of the contrast ratio can be exceeded 900 times.

We investigate the extraordinary optical transmission of a subwavelength elliptic hole array in a metal by a proposed simple method. The transmission strength depends on the polarization direction of the incident light. The polarization excitation ratio of the surface plasmon polariton (SPP) governs the transmissivity. There is an interplay between the adjacent holes which is caused by the transverse magnetic filed of SPP on the surfaces of the metal.

The extraordinary optical transmission (EOT) through a subwavelength metal double-slit structure is calculated to study in detail the correlation between the single-slit and inter-slit effects on the transmissivity. A transmissivity formula is put down which retrieves the numerical results from the finite-difference time-domain simulation method. After some reasonable approximations made, the formula is expressed as the product of two periodic functions, determined by the length of a single slit and inter-slit distance, respectively. This simplified form shows that the interplay between the single-slit and inter-slit effects is almost negligible.

We propose a dressed subwavelength metal slit structure, which is formed by adding a thin metallic grating near the slit entrance with a distance. The simulation computation by means of the finite-difference time-domain method shows that the transmissivity can be substantially enhanced by 30 times compared with the conventional metal slit structure. The transmission spectrum exhibits two characters of the Fabry-Perot resonance and a left-shift. The introduced grating has two effects: (1) more energy is collected from the incident plane, and (2) the effective dielectric region in the slit is extended to the region out of the entrance.

We propose a combination structure which consists of a subwavelength metal slit filled periodically with two different dielectrics to modulate slit plasmon polaritons (slit-PPs). The transmission spectra are simulated by the finite-difference time-domain method and the photonic band gaps are observed. The theoretical formula to calculate the band-gap structures is deduced and the calculation results agree satisfactorily with simulated results. This structure can be termed as slit-PP crystal.

In the past few years, new applications of terahertz wave have given rise to the development of intense terahertz wave source and modulation of terahertz wave [1–4]. However, rigorous experimental conditions or few theoretical explanations were in these works. In this paper, a method to enhance and control the THz pulse generation in air plasma by external electric field is proposed. Two theoretical models, the optics Four-Wave-Mix-Frequency and the electrodynamics electromagnetic radiation are given to explain the results of the proposed method respectively.

We present the time-domain analysis of the extraordinary optical transmission of the slits milled on the thin metallic film. We employ the finite-difference time-domain method to study the variations of the transmission energies with the sampling time received by several monitors that are placed on the specified positions in the structure. It is found that the physical origin of the related phenomenon may be contributed by a combining effect of single-slit effect and interslits effect. The single-slit effect is brought by the excitation of surface-plasmon polaritons from the isolated slit and the interslits effect is caused by phase interference of the transmitted waves from two slits. When the transmissivity of an isolated slit is adjusted to a maximum, total transmissivity of the grating is never governed by phase interference and can be qualified to the contribution from a single slit alone.

We demonstrate theoretically that an optical one-way transmission device can be constructed by inserting an epsilon-near-zero (ENZ) prism into a metal slit. Similarly to the junction in the electron diode, the oblique surface of the ENZ prism is a key factor that can block the transmission of the light striking on it and allows the transmission of the light leaving from it. The performance of the device is shown by numerical simulation based on the finite-difference time-domain technique.

In this presentation, we investigate the properties of the PBG's in the MPC's in detail. We calculate the band structures of two-dimensional (2D) MPC's which are composed of magnetic rectangular/square scatterers in rectangular/square lattice. The plane-wave expansion method is employed. We find that the PBG's in the MPC's strongly depend on physical and geometric parameters in the structures, such as the shapes of the 2D lattice and the scatterers, the permeability of the scatterers, and so on. Therefore, the introduction of magnetic material into the PC's may diversify the favorable candidates of the PC's in nature. It is expected that the PBG's in the MPC's can be engineered by changing the relevant parameters to match various practical applications in optical devices.