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Abstract In this paper, we present a new type of isolator based on one-way surface magnetoplasmons (SMPs) at microwave frequencies, and it is the first time that an experimental prototype of isolator with wideband and ultra-high isolation is realized using SMP waveguide. The proposed model with gyromagnetic and dielectric layers is systematically analyzed to obtain the dispersion properties of all the possible modes, and a one-way SMP mode is found to have the unidirectional transmission property. In simulation and experiment with metallic waveguide loaded with yttrium–iron–garnet (YIG) ferrite, the scattering parameters and the field distributions agree well with the analysis and verify the one-way transmission property. The isolation is found to be as high as 80 dB and the typical value of insertion loss is 1 dB. Besides, the one-way transmission band can be controlled by changing the magnetic bias. From theoretical analysis and simulation, it is found that with a tiny value of 10 Oe of the magnetic bias, the relative bandwidth can be tuned to be greater than 50%. Compared with conventional isolators, this one-way SMP isolator has the advantages of ultra-high isolation, wide relative frequency band, and requires much smaller bias field, which has promising potential in non-reciprocal applications.

Abstract Metasurfaces are capable of fully reshaping the wavefronts of incident beams in desired manners. However, the requirement for external light excitation and the resonant nature of their meta-atoms, make challenging their on-chip integration. Here, we introduce the concept and design of a fresh class of metasurfaces, driven by unidirectional guided waves, capable of arbitrary wavefront control based on the unique dispersion properties of unidirectional guided waves rather than resonant meta-atoms. Upon experimentally demonstrating the feasibility of our designs in the microwave regime, we numerically validate the introduced principle through the design of several microwave meta-devices using metal-air-gyromagnetic unidirectional surface magneto-plasmons, agilely converting unidirectional guided modes into the wavefronts of 3D Bessel beams, focused waves, and controllable vortex beams. We, further, numerically demonstrate sub-diffraction focusing, which is beyond the capability of conventional metasurfaces. Our unfamiliar yet practical designs may enable full, broadband manipulation of electromagnetic waves on deep subwavelength scales.

Abstract The long-term erosion of rock by solution can induce a series of karst problems. Therefore, this study focused on limestone and conducted dynamic dissolution experiments under deionized water and CO2 solution conditions to study the deterioration mechanism of limestone under nonequilibrium conditions. The results showed that the degree of degradation of the mechanical properties of the samples in a CO2 solution was obviously greater. In a deionized water environment, the degradation of the mechanical properties of the sample is mainly controlled by the physical softening action of the solution. In the CO2 solution environment, the degradation process can be divided into two stages. In the early stage of the experiment (10 days to 20 days), the degradation of mechanical properties of the sample is also controlled by the physical softening action of the solution. With increasing soaking time, the main rock-forming minerals of limestone gradually react with the CO2 solution, the degradation of the sample is controlled mainly by the chemical corrosion of the CO2 solution, and its degradation rate is much greater than that of physical softening. The results can be used as a reference for assessing the long-term stability of underground engineering in limestone karst development areas.

Abstract In order to employ periodic corrugated microstrip lines for reducing or suppressing electromagnetic interference in high‐speed or high‐frequency circuits, a precise method is necessary to calculate and measure the characteristic impedance of periodic microstrip lines. The equation for characteristic impedance (depending on frequency) of lossless periodic microstrip lines was obtained based on the transfer matrix method. A time domain pulse was used to measure the instantaneous impedance of conventional microstrip lines, and when the instantaneous impedance does not change with distance, it can be identified as the characteristic impedance of microstrip lines. However, when the time‐domain pulses are employed to measure the instantaneous impedance of periodic microstrip lines, rapid oscillations occur with distance. Therefore, a standard for spacing between adjacent grooves in the microstrip line can be suggested by analysing the interaction between the time‐domain pulses and the microstrip line grooves. Once such a standard is satisfied, many grooves etched along the microstrip line would no longer be distinguished by the time‐domain pulses. Such a principle and method can be used to determine the instantaneous impedance for the microstrip lines that have periodic grooves. On the other hand, when several periodic structures with different lattice constants coexist on a microstrip line, they can also be distinguished via the instantaneous impedance. A time domain reflectometer was used for measuring the instantaneous impedance of periodic microstrip lines, and the measured results are in agreement with the theoretical analysis.

Abstract Unidirectional surface waves in nonreciprocal plasmonic platforms with nonlocal effects have been a topic of significant interest and some controversy. In this study, we present a scheme to achieve unidirectional surface magnetoplasmons (USMPs) with large modal areas at terahertz frequencies. Such large-area USMPs (LUSMPs) exist in a metal-UENZ (uniaxial- $$\varepsilon $$ ε -near-zero)-Si-InSb structure under external magnetic field, where the effect of nonlocality is included. The field of the LUSMP extends almost uniformly in the UENZ layer with a thickness of wavelength scale, thus its modal size can be represented by the UENZ-layer thickness. Due to the modal energy primarily distributed in the thick UENZ layer, the nonlocality-induced leakage of the LUSMP is significantly reduced by an order of magnitude, compared to previous USMP existing at interface between InSb and opaque isotropic medium. Due to their large modal sizes, such LUSMPs can be efficiently excited by terahertz radiations directly from free space. In addition, LUSMPs offer high degree of freedom for manipulating terahertz waves, such as energy squeezing and trapping. Based on LUSMPs, a terahertz free-space isolator is also developed. Our findings have important implications to the development of innovative plasmonic devices in terahertz regime.

Abstract Peierls transition that modifies electronic band structure has attracted intensive attention in solid state physics. In the present work, we report that a photonic analog of Peierls transition has been observed in a 1-D triangular metal diaphragm array, where the photonic bandgap structures have been designed at will by adjusting periodically metal diaphragm positions. It is shown by the numerical analysis that the transmission and radiation effect of the present periodic metal structure designed through the Peierls transition rule exhibits the behavior significantly different from an original periodic structure with each unit cell containing a metal diaphragm. The near- and far-field measurement results are in good agreement with our theoretical simulation. The present effect of photonic Peierls transition can serve as a working mechanism for designing new types of guided wave devices. It can be seen that the photonic Peierls transition would be one of the simplest ways for modifying the transport characteristics of electromagnetic waves in periodic structures.

Abstract Since a planar periodic transmission line can suppress drastically the electromagnetic coupling, it would be advantageous to use such a kind of transmission lines in solving the problem of miniaturization of circuit area. By adjusting the lattice constants and geometric parameters of periodic microstrip lines, a time domain characteristic impedance that is the same as that of conventional microstrip lines (CMLs) can be achieved. Such periodic microstrip lines can therefore be used to trick high-speed digital signals, causing a digital signal to misjudge the time domain characteristic impedance of the transmission lines. The theoretical analysis has been verified by our experimental measurement results. Besides, a specific expression for the characteristic impedance of lossless periodic artificial materials is deduced by a circuit model and a standard of misidentification for the characteristic impedance of periodic microstrip lines is given for the digital signals.

In order to directly observe the conversion between guided-wave modes and leaky-wave modes in a periodic structure, quadrilateral periodic metal diaphragms arranged in two ways on metal surfaces were analyzed. In the first scheme, each unit cell in the periodic structure contains a metal diaphragm, of which the dispersion characteristics of periodic structures were analyzed by the finite element method. The results of the numerical simulation show that by adjusting lattice constants of periodic structures and geometrical parameters of metal diaphragms, the transmission bandwidth of the present 1-D periodic metal diaphragm structures could be limited to X-band, where the transmission characteristics are easy to be measured. In the second scheme, a pair of mirror-symmetric and staggered quadrilateral metal diaphragms is introduced into a unit cell. It can be found in the theoretical calculation that a new dispersion curve, which passes through the light line in a high frequency range, can be exhibited. The propagation constants of dispersion curves become complex numbers and provide highly directional electromagnetic radiation that scans as the frequency changes. After the relative positions of the two metal diaphragms were properly adjusted, the frequency range of the forbidden band gap between two dispersion curves can be minimized, so as to increase the transmission bandwidth of the 1-D periodic metal structures. The experimentally measured results show that the dispersion curves of the two periodic structures were highly consistent with the theoretical results. The narrowing of the band gap could be verified by measuring the $S$ -parameters. The near-field measurement of the periodic metal structures can demonstrate the conversion between the guided-wave modes and the leaky-wave modes, and the far-field measurement can show the frequency dependence of beam elevation. We expect that these artificial material structures could be widely used for designing new microwave and terahertz band devices.

In the freezing process, the soil is accompanied by heat conduction, heat release for ice-water phase change, phase change interface movement, and a change in thermal diffusion coefficient, which is a complex nonlinear problem and is hard to solve. This study uses the enthalpy method to establish a unified control equation for heat conduction in the entire calculation region (including the solid-phase zone, liquid-phase zone, and phase change interface). It solves the equation numerically, relying on the D2Q4 model of the lattice Boltzmann method, and determines the evolution of the temperature field and solid-liquid phase change interface position with time. The trends in the soil’s temperature field evolution and freezing front movement under unilateral and bilateral cold sources are discussed using an example from an artificial freezing project. The results show that when −10°C is taken as the limit for freezing wall temperature, the freezing wall thickness developed at 5, 10, 20, 30, and 40 days under the unilateral cold source is 0.24, 0.33, 0.47, 0.57, and 0.66 m, respectively. The overall temperature in the soil drops below −13.6°C and −26.4°C at 35 days and 45 days under the bilateral cold sources. These values can provide a basis for engineering design.

This paper proposed a kind of guard traces based on a subwavelength periodic structure to reduce the far-end crosstalk (FEXT) of parallel microstrip lines in the PCB. This technology can be used to improve the false triggering and signal transmitting capacity of a multiconductor transmission line circuit system. In order to explore the present novel guard trace effect on isolating electromagnetic interference (EMI), the frequency response of the mutual capacitance and mutual inductance of the overall circuit system was provided and an equivalent circuit model was built. In comparison to the conventional microstrip line for isolating the EMI between parallel microstrip lines, the novel guard trace can efficiently reduce the mutual capacitance and mutual inductance of the overall circuit system. Thus, it is favorable for suppressing the crosstalk between microstrip lines. The $S$ -parameters calculation result showed that this kind of subwavelength periodic microstrip guard trace can isolate the EMI between two microstrip lines more effectively. Particularly, the conventional grounded guard trace needs a lot of dense grounded holes, which severely influences the wiring design of various layers of a multilayer circuit board. However, the proposed guard trace requires only one grounded hole, which has little influence on the circuit wiring of each layer of a multilayer printed circuit board. In our experiment, the step function signal of 30 ps rise time was imported into one microstrip line to measure the FEXT of the other microstrip line. It was demonstrated by the measurement result that the subwavelength periodic microstrip guard trace can reduce the FEXT to be below 5% of the transmission signal amplitude and is more flexible in practice. In compliance with the actual demand for a high-speed circuit, three isolation structures were proposed, and their isolation effects on the electromagnetic coupling between microstrip lines were verified individually.

In this study, we established, for the first time, an equivalent circuit model for coupled subwavelength periodic microstrip lines (CSPMLs) over a wide frequency range. The circuit composed of two identical and parallel subwavelength periodic microstrip lines has two fundamental modes, i.e., odd and even modes. Based on the two fundamental modes, the finite element method (FEM) is used to extract the circuit parameters, especially the frequency-dependent behavior of the mutual capacitance and mutual inductance for the CSPMLs. The $S$ -parameters evaluated by full-wave simulation and the circuit model were highly consistent with a maximum deviation of only 0.249 dB for transmission coefficient below 15GHz. Because of reduced the mutual capacitance and mutual inductance, the crosstalk between two adjacent microstrip lines could be suppressed by optimizing the subwavelength periodic structure. The measured characteristic impedances for differential and common signals of CSPMLs also agree well with the numerical results. Therefore, we expect that the application of circuit models of CSPMLs would accelerate the use of metamaterial technology in the existing high-speed circuit systems.

Unidirectional electromagnetic modes have significant potential for routing electromagnetic radiation and are highly desirable for various applications, such as isolators, splitters, and switches. In this study, we theoretically investigate surface magnetoplasmons (SMPs) in a four-layer structure consisting of a perfect magnetic conductor (PMC)–semiconductor–dielectric–metal, which exhibits complete unidirectional propagation. We extend this structure to a 3D model by decreasing the width of the PMC-semiconductor part to an appropriate value and demonstrate that the SMPs in the proposed 3D waveguide retain complete unidirectional propagation. Our findings indicate that the unidirectional SMPs are robust to backscattering caused by surface roughness and defects. Moreover, the proposed 3D waveguide can be efficiently coupled to conventional microstrip line waveguides. Our results (based on the numerical method) demonstrate that SMPs based on semiconductors offer a promising approach to creating devices with new functionalities in the terahertz regime below the diffraction limit.

A viable wide-band circuit model of parallel corrugated differential transmission line is established. By solving for the even- and odd-modes in this structured differential transmission line, the equivalent capacitance, inductance, resistance, and conductance per unit length are calculated, then the characteristic impedances of differential and common signals are obtained. The S-parameters obtained from the equivalent circuit model agree well with the full-wave simulation results with a deviation of only about 0.036 dB in the frequency range of 10 GHz. Experimentally, the characteristic impedances are measured for the differential and common signals using a time domain reflectometer (TDR). The deviation between the experimental and theoretical results was less than 1.05%. Based on the equivalent circuit model, it is feasible to implement this type of structured differential line directly into real circuits.

According to the existing personnel structure, quantity, development strategy, and market demand of the Shuohuang Railway Company’s operation and maintenance project, the demand quantity of various employees of the company for the past three years is predicted, and a human resource optimization model based on existing human resources and future plans is established. Then, the optimal solutions of the two mathematical models were calculated and analyzed using LINGO software. Finally, combined with the actual situation, the optimal allocation of human resources for the operation and maintenance project of KY company was obtained. The following conclusions are obtained. (1) For the optimal allocation model of existing human resources, the maximum net profit of the optimal staffing model is CNY 3258000. (2) The human resources allocation cost of the minimum dismissal model is CNY 81000. (3) The human resources allocation cost of the lowest cost model is CNY 15500. The research results can effectively guide the human resource management of the operation and maintenance project of the Shuohuang Railway Company, and have important theoretical and practical significance for further analysis of human resources model and its optimal allocation method.

Abstract A microwave one-way waveguide of three-dimensional configuration is proposed and investigated theoretically. In this waveguide there exists a complete one-way propagation band, where the mode propagates only in one direction and can be immune to backscattering. By terminating the one-way waveguide with metal slab, one-way propagating waves in this waveguide system can be stopped at the terminal end without any backscattering. Meanwhile, a hotspot with extremely enhanced magnetic-field amplitude is generated in this 3D waveguide system. For an incident microwave pulse, the trapped wave packet can be compressed to deep subwavelength scale besides the magnetic field enhancement. Moreover, the magnetic field enhancement of trapped waves can be further largely increased by tapering laterally the waveguide system. The approach for trapping microwaves has promising applications in magnetic sensing and magnetic non-linearity.

A lattice Boltzmann model is proposed to simulate the forming process of artificial frozen soil wall. The enthalpy method is applied to deal with the latent-heat source term, and the adjustable thermal diffusivity is utilized to handle the change of thermophysical parameters. The model is tested by the heat conduction with solid–liquid phase change in semi-infinite space, which shows a good consistence between the numerical and analytical solutions, and the mesh resolution has little effect on the numerical results. Lastly, the development of frozen soil wall is discussed when the freezing pipes are arranged in a square. The results show that the evolution of temperature field with time is closely related to the distance from the freezing pipe. For the soil near freezing pipe, the temperature gradient is larger, the soil temperature drops rapidly and freezes in a short time. The time history curve of temperature is relatively smooth. For the soil far away from freezing pipe, the temperature evolution curve has obvious multistage, which can be divided into four stages: cooling, phase change, partly frozen and completely frozen. The spacing of freezing pipes has a significant influence on the overlapping time of artificial frozen soil wall, and there is a power function relationship between them.

Slip boundary has an important influence on fluid flow, which is non-negligible in rock micro-fractures. In this paper, an improved pseudo-potential multi-relaxation-time (MRT) lattice Boltzmann method (LBM), which can achieve a large density ratio, is introduced to simulate the fluid flow in a micro-fracture. The model is tested to satisfy thermodynamic consistency and simulate Poiseuille flow in the case of large liquid-gas density ratio. The slip length is used as an index for evaluating the flow characteristics, and the effects of wall wettability, micro-fracture width, driving pressure and liquid-gas density ratio on the slip length are discussed. The results demonstrate that the slip length increases significantly with the increase of the wall contact angle in rock micro-fracture. And the liquid-gas density ratio has an important impact on the slip length, especially for the hydrophobic wall. Moreover, under the laminar flow regime the driving pressure and the micro-fracture width has little effect on the slip length.

Surface plasmon polaritons (SPPs) propagating along a structure consisting of a single row of metallic wedges periodically protruding out of a planar metallic surface are investigated theoretically. It is shown that such a structure can sustain a mode of spoof SPPs in the terahertz region, whose fields are highly confined in the transverse plane. The guiding mode in the structure possesses excellent properties such as good modal shape, large propagation length, and low bending loss, making it a promising candidate for routing terahertz radiation in highly integrated circuits. [ABSTRACT FROM AUTHOR]

Spoof surface plasmon polaritons (SPPs) propagating along a perfect electric conductor (PEC) film with an array of cut-through slits are analyzed along with both the symmetric and asymmetric dielectric environments of the film. The studies have shown that a structured PEC film cannot be mapped again into the dielectric layer with an effective permittivity when this predicted permittivity is smaller than the permittivity of the substrate or superstrate.

Nowadays, the terahertz (THz) communication is believed to be a potential solution to the communication blackout for reentry vehicles. In this paper, a numerical hypersonic fluid model was introduced to obtain the realistic plasma sheaths. The onboard antenna which is installed on the wall was assumed to be conformal. The transmission of obliquely incident THz waves in the plasma sheaths was analyzed. According to this paper, the power transmission coefficient decreases with the increase of reentry speed since both the electron density and the electron collision frequency near the onboard antenna increase with the reentry speed. In addition, the relation between the wave transmission and the reentry speed is revealed. The power transmission coefficient decreases with the increase of incident angle, because the conformal antenna cannot receive the field component which is perpendicular to the wall. Two supplemental schemes to enhance the transmission rate for THz signals were discussed based on this paper. [ABSTRACT FROM AUTHOR]

The communication 'blackout' in the reentry stage of a space mission is a serious threat to the reentry vehicle. The terahertz (THz) technology is supposed to be a potential solution to the 'blackout' problem in the recent decade. In the present paper, the relation between the THz waves' transmission in the reentry plasma sheath and the angle of attack (AOA) of the vehicle is investigated. A three-dimensional numerical model is introduced in order to obtain the plasma parameters in the reentry plasma sheaths. The computation results show that both the electron density and the electron collision frequency vary with the AOA. As results, the transmission rates for the THz waves vary with the AOA as well. According to the analysis, microwave communication system is very likely to suffer from the 'blackout' in the reentry stage. The THz scheme is an effective solution. The fluctuation of AOA may weaken the signal strength received by the onboard antenna. On the other hand, keeping the AOA in an appropriate range is helpful for strengthening the received THz signals. Also, the AOA for the best THz communication quality is obtained according to the analysis. [ABSTRACT FROM AUTHOR]

Communication 'blackout' is a big challenge for modern space engineering. In the recent decade, the terahertz (THz) technology is believed to be an effective solution for the 'blackout' problem. Many research works about the transmission of THz waves in plasma slabs have been carried out. According to those works, the radio attenuation of THz waves in plasma slabs strongly depends on thickness of the slab, electron density, electron collision frequency and temperature. However, few previous works have paid attention to realistic reentry plasma sheath. In the present paper, a hypersonic fluid model is introduced in order to investigate the structure of the realistic plasma sheath which covers a blunt coned vehicle. The scattering matrix method is employed to study the transmission of THz waves in realistic plasma sheath. According to the present study, the wave frequency, electron density and collision frequency are the most significant factors which determine the attenuation of the THz waves in the plasma sheath. Since the whole plasma sheath is inhomogeneous, to install the antenna at an appropriate position helps mitigate the 'blackout'. For the blunt coned reentry vehicle, installing the antenna on the wall close to the bottom is helpful for mitigating the 'blackout' problem. [ABSTRACT FROM AUTHOR]

The guiding properties of spoof surface plasmon polaritons (SPPs) in an array of hollowed-out metallic blocks standing on a metallic surface are theoretically investigated in this study. For such spoof SPPs, there exists an additional guiding mode except for the fundamental mode and the former is closely related to hollowing out metal blocks. The dispersion band of this additional mode has a negative slope (corresponding to a group velocity) and it intersects the light line and then enters the radiation region as the frequency grows, which leads to a frequency steering pencil-like radiation. The transmission and radiation properties of the additional mode of spoof SPPs are finally verified experimentally. [ABSTRACT FROM AUTHOR]

A nanoantenna that consists of a pair of perpendicular diabolo metal elements with a common central junction is proposed for creating magnetic field enhancement. It is shown that such a nanoantenna can generate a single magnetic hot spot for any polarization state in near-infrared frequency range, strongly confining and enhancing magnetic field under less restrained conditions. The magnetic spectral response of the nanoantenna can be tailored as will by altering its geometric parameters. Moreover, this cross-diabolo nanoantenna can preserve the polarization character of any in-plane dipole in the far-field patterns with high fidelity. [ABSTRACT FROM PUBLISHER]

In this paper, we show that surface plasmon polaritons (SPPs) can be sustained by a single row of holes periodically drilled on a perfect electric conductor surface. These SPPs can be strongly confined in the transverse plane and they possess an excellent modal shape. In the terahertz regime, large propagation length is available for highly confined SPPs on a real-metal surface waveguide. As the dispersion characteristics of such SPPs can be controlled by the surface geometry, unusual total reflection phenomenon occurs when waves travel along a nonuniform surface waveguide with gradually increasing hole depths. [ABSTRACT FROM AUTHOR]

The coupling between negative and positive index medium waveguides is investigated theoretically in this paper. A coupled mode theory is developed for such a waveguide system and its validity is verified. Interesting phenomena in the coupled waveguides are demonstrated, which occur in the case when the negative index medium waveguide in isolation guides its mode backward. A new type of coupled mode solution that varies exponentially with the coupling length is found in the special case when the propagation constants of two individual waveguides are nearly the same. A coupler operating in this case is insensitive to the coupling length, and its coupling efficiency can reach 100% as long as the coupling length is long enough. However, when the propagation constants of the two individual waveguides differ greatly, the coupled mode solution is still a periodic function of the coupling length, but the coupled power is output backward. In addition, the modes in the composite waveguide system are also studied using the coupled mode theory, and their fundamental properties are revealed. [ABSTRACT FROM PUBLISHER]

A novel elliptical-hole photonic crystal fiber (PCF) with double defect is theoretically investigated, and its high birefringence [including both the phase-index birefringence (PIB) and the group-index birefringence (GIB)] is demonstrated, which can reach an order of 10-2 Such a PCF can especially have a very high PIB, with a negligible GIB in a small band of normalized frequencies. The PIB of this PCF is much higher than that of the circular-hole PCF with double defect, under comparable parameters. Compared with the elliptical-hole PCF with single defect, the present PCF possesses the advantages of both a higher PIB and a larger modal area for modest ellipticities; thus, it is more suitable in linear applications, as well as in fabrication. Moreover, a novel single-polarization single-mode (SPSM) PCF with a broad wavelength band is proposed and demonstrated. In addition, a new approach in designing broadband SPSM PCFs is suggested. [ABSTRACT FROM PUBLISHER]

An extended finite-difference time-domain (FDTD) method with inclusion of material dispersion for the full-vectorial analysis of photonic crystal fibers (PCFs) is presented in this paper. In order for this extended FDTD method to obtain a fast convergence and high accuracy, a constitutive-parameter averaging technique is employed. Numerical results for a typical PCF verify the validity of the extended FDTD method. With this FDTD mode solver, a new birefringent PCF is also investigated, and interesting results are obtained in this paper [ABSTRACT FROM PUBLISHER]

We propose a scheme of guiding and manipulating terahertz waves that features tight confinement and large propagation length, even when the waveguide lateral dimensions are well in the subwavelength regime. In a tapered structure of the proposed groove waveguide, the guided mode can be stopped at different positions for different frequencies when it travels along the waveguide. Additionally, we demonstrate that nearly 100% transmission through a sharp 90° bend can be achieved in this groove waveguide. [ABSTRACT FROM PUBLISHER]

A layered metamaterial which is predicted by the effective medium theory to be an anisotropic medium with partial zero permittivities is analyzed carefully. It is shown that such a material has a dispersion relation in parabolic form, which is quite different from the known ones. This material may be viewed as a homogeneous medium but is spatially dispersive strongly. The structured medium may support either forward wave or backward wave, depending on the magnitude of the wave vector. Moreover, it is demonstrated that this medium with parabolic dispersion is especially suitable for the transmission of Gaussian beam with subwavelength width. [ABSTRACT FROM AUTHOR]

In this paper, a novel coaxial waveguide comprising a hollow cylinder made of a magneto-optical material and a metal wire at the axis is proposed. The surface magnetoplasmon and guided modes of the waveguide are studied. The results show that the dispersion relation and electromagnetic field distribution are highly sensitive to the operating frequency and physical dimensions of the structure. It is demonstrated that there exist three different types of modes, that is bulk mode, surface mode, and regular mode. By adjusting the operating frequency and reducing the inner diameter of the hollow cylinder, the regular mode is suppressed and only the surface mode remains, which shows one-way propagating property. Moreover, the one-way surface mode is robust against backscattering at defect and surface roughness, which has good potential in practice. The unique properties of this waveguide are demonstrated through mode analyzes as well as numerical simulations. [ABSTRACT FROM AUTHOR]

The subwavelength focusing based on surface plasmon polaritons has been widely explored in tapered metallic structures. However, the efficiency of energy localization is relatively weak, largely due to high propagation loss and strong back reflection. Here, we propose a three-dimensional (3D) straight-tapered one-way surface magnetoplasmon (SMP) waveguide with the end surface of ∼10−4λ0 × 10−4λ0 to achieve energy focusing in the microwave regime. Due to low propagation loss of SMP, we achieve huge magnetic field enhancement in such an ultra-subwavelength area, by five orders of magnitude. Instead of using an external static magnetic field, our proposed SMP waveguide relies on remanence, which is very convenient for operating practical 3D applications. These results show promising applications in magnetic-field enhancing or quenching fluorescence, luminescence or nonlinearity of two-dimensional materials, novel scanning near-field microwave microscopy and energy storage. [ABSTRACT FROM AUTHOR]

A photonic microwave filter based on fiber loop and fiber Bragg gratings (FBGs) is applied in a radio-over-fiber (RoF) system to suppress the relative intensity noise (RIN) of laser and the amplified spontaneous emission (ASE) noise of erbium-doped fiber amplified (EDFA). The experiment results show that the signal-to-noise ratio (SNR) of the system can be effectively improved by using such a noise filter in the system. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 305–307, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21333 [ABSTRACT FROM AUTHOR]

Deals with a study on the use of a genetic algorithm to design a two-dimensional anisotropic photonic crystal. Method to decrease the symmetry of a photonic bandgap structure; Dielectric materials which form the crystal; Division of the unit cell of the square lattice.

A novel directional coupler with a left-handed material (LHM) layer between two single-mode (SM) waveguides of usual material is introduced. The coupling system is analyzed with the supermode theory. It is shown that such an LHM layer of finite length can shorten significantly the coupling length for the two SM waveguides. An LHM layer with two slowly tapered ends is used to avoid the reflection loss at the ends. [ABSTRACT FROM PUBLISHER]

Terahertz one-way edge modes in truncated photonic crystals (PhCs) are investigated theoretically. The PhC consists of a square array of air columns in a semiconductor. By applying an external dc magnetic field in the PhC, a band gap is generated by lifting the degeneracy point of the lowest two bands. Based on this band gap, the edge mode always exists in the truncated PhC for any boundary cutting, and it may propagate unidirectionally or bidirectionally, closely depending on the PhC boundary shape. It is shown that for the one-way edge mode, the PhC boundary cutting has a remarkable influence on the propagation length when the semiconductor loss is taken into account. A boundary structure is introduced into the PhC system for weakening the loss effect, and the propagation length of the one-way edge mode can be increased nearly by twice by optimizing the boundary parameters. [ABSTRACT FROM AUTHOR]

Power splitters have been widely studied in the fields of radio frequency and integrated photonics, however, conventional splitters generally suffer from poor transmission and limited bandwidth. Here we propose a novel tunable T-shaped power splitter utilizing one-way waveguide that is composed by the yttrium–iron–garnet–air–metal configuration with one static magnetic field applied. We show that the transmission efficiency of such a splitter reaches 100% in the lossless case due to the suppression of reflection by the one-way waveguide. By introducing a defect in the junction area, the splitting ratio of the splitter can be gradually tuned by varying the external magnetic field, and large operation bandwidth can be achieved for a given splitting ratio. Our results presented here focus on the radio frequency, and the concept can easily be applied to the photonic area. [ABSTRACT FROM AUTHOR]