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To improve the reliability of simulation results, uncertainty analysis methods were developed in the Electromagnetic Compatibility (EMC) field. Random variables are used to describe random events. The more random variables you have, the less efficient the simulation is. Therefore, many high-accuracy methods have the problem of dimensional disaster, which means the calculation efficiency decreases exponentially with the increase of the number of random variables. A random variable reduction strategy based on sensitivity analysis method is proposed in this paper, so as to improve the computational efficiency of the global uncertainty analysis method.

Uncertainty analysis is a research hotspot in the field of electromagnetic compatibility (EMC) simulation. The stochastic collocation method (SCM) is considered particularly suitable for uncertainty analysis in the EMC field because it is characterized by a high level of computational efficiency and accuracy while requiring no replacement solver. However, the post-processing process of the SCM is too complex, which will seriously limit its application in many industrial environments such as real-time simulation analysis. Multi-element grid (MEG) is a novel uncertainty analysis method recently for successful application in another area. It is proved that its calculation accuracy is same as the SCM, and its post-processing process is facile. This paper introduces the MEG to the EMC field and makes a detailed comparison between it and the SCM in performance, aiming to apply uncertainty analysis to solve more practical EMC engineering problems.

The planar integrated EMI filter has been widely used because of its small size and good high-frequency characteristics. During the production process, if the electrical parameters of the integrated LC structure can be accurately identified, it will help improve the high-frequency characteristics of the filter. However, this identification problem is a multi-peak problem, which can easily fall into a local optimal solution. Based on the Feature Selective Validation method, this paper proposes an improved Immune Algorithm. The proposed method keeps changing the fitness function in the iterative process to avoid the algorithm falling into the local optimal solution. Finally, comparing with the measured impedance characteristic curve, it is verified that the proposed method is more accurate than the common Immune Algorithm.

N-type heavy doping and tensile strain can significantly improve the luminescence efficiency of Ge materials. The active region of the quantum dot(QD) structure can realize high luminous efficiency...

A tunable broadband terahertz (THz) absorber is designed based on vanadium dioxide metamaterials. Numerical results shown that the bandwidth of absorption rate above 90% is 1.25 THz. The absorption rate can be continuously tuned from 15% to 96%, when vanadium dioxide transits from insulator phase to metal phase. In addition, the absorber has the advantages of polarization insensitive, wide-angle and quick response. May be applied to fields such as THz sensors, detectors and switches.

Uncertainty analysis plays a significant role in electromagnetic compatibility (EMC) simulation, but suffers from convergence determination thereby reducing simulation accuracy and computational efficiency. In this paper, an improved mean equivalent area method is proposed to enhance calculation accuracy. It shows that, using a benchmark example, the proposed method successfully achieves the convergence determination of the stochastic reduced order models (SROMs), and realizes further promotion of uncertainty analysis method.

As the main pressure components of pressure vessels, the mechanical performance of cylinders and heads affects the normal operation of pressure vessels. At present, no unified theoretical formula exists for the connection region between an elliptical head and the cylinder. Therefore, the authors consider the standard elliptical head as the research object. First, the theoretical stress calculation formula is deduced according to the deformation continuity equation. Second, the stress is experimentally measured using an internal-pressure thin-walled-vessel stress measurement device, and the theoretical and experimental stress values in the discontinuous region between the elliptical head and cylinder are analysed and compared to verify the accuracy and applicability of the theoretical stress calculation formula. The results show that the theoretical stress calculation formula in the discontinuous region between the elliptical head and cylinder is valid. By comparing and analysing the theoretical and experimental stress values, the accuracy and applicability of the theoretical stress calculation formula in the discontinuous region are verified. The findings can provide guidance for the stress measurement of internal-pressure vessels.

In view of the phenomenon that there is no uniform theoretical formula for the connection area between the elliptical head and the cylinder, the author takes the standard elliptical head as the research object. Firstly, the theoretical stress calculation formula of the elliptical head and the discontinuous area of the cylinder is derived according to the deformation continuity equation. Secondly, the experimental stress is measured by means of the internal pressure thin-walled vessel stress measuring apparatus, The theoretical stress and experimental stress in discontinuous region are analyzed and compared to verify the accuracy and applicability of the formula for calculating the theoretical stress of the elliptical head and the cylinder discontinuity region. The results show that the theoretical stress calculation formula of discontinuous region of elliptical head is obtained according to the equation of deformation continuity, edge force and edge moment, internal force and internal moment; The internal pressure load is kept unchanged, and for the theoretical longitudinal stress, the constant stress is greater than 0, which is the tensile stress, and decreases gradually from the vertex to the equator; For the theoretical circumferential stress, the change trend is more complex, which can be divided into three stages, and there is pressure stress. At the vertex, the magnitude of the meridional stress and the circumferential stress is approximately equal; The change of the change from point 8 to point 10 is affected by discontinuous stress, and the change trend is abrupt; The theoretical stress and experimental stress in discontinuous region of elliptical head are analyzed and compared, and the accuracy and applicability of the formula are verified. The results are of great significance for the stress measurement of internal pressure vessels.

A novel switchable multi-wavelength erbium-doped fiber laser based on random distributed feedback is demonstrated in this paper. Based on loop mirror to form a half-opened laser cavity, typical random laser radiation is achieved with an obvious threshold behavior as a function of pump power. Switchable multi-wavelength lasing operation is also achieved by changing attenuation value through the variable optical attenuator. Due to the efficient gain from the pumped erbium-doped fiber, a low threshold power of 22 mW is achieved, which is much lower in magnitude than that of previously reported conventional random fiber lasers.

A fiber-optic refractive index (RI) sensor based on fiber loop ring-down (FLRD) technique with an S fiber taper (SFT) structure is proposed and experimentally investigated. The SFT is served as an in-line Mach–Zehnder interferometer and inserted into a compensated fiber loop for RI measurement. By optimizing the parameters of the fiber loop, the quality of the ring-down signals is improved effectively. The surrounding refractive index can be conveniently measured by interrogating the ring-down time of the fiber loop. The experimental results demonstrate that the proposed sensor has a high sensitivity of $- 3128.954\,\,\mu \text{s}$ /RIU in the measurement range of 1.3330–1.3682. The proposed RI sensor combines the specialties of SFT interferometer and FLRD technology, which could be a good candidate in applications.

A broadband terahertz (THz) metamaterial absorber (MA) based on a double composite structure layer on a metallic board is proposed. Each layer consists of four different sized square metallic plates. The absorbing properties and variation laws have been numerically investigated with FDTD method. The numerical results show that the absorber bandwidth is 0.642 THz with the central frequency around 1.901 THz. The physical mechanism of the broadband absorber can be explained as the overlapping of eight closely resonance frequencies using the analysis of magnetic field distribution. Besides, the proposed absorber has several advantages, including the polarization insensitive, large angle tolerance and potential to be applied for integrated THz photoelectric devices.

A new type of terahertz fiber is presented based on composite lattice photonic crystal bandgap. The cladding is filled selectively with the nematic liquid crystal 5CB which is sensitive to the electric field. The terahertz wave can be modulated by using the electric field to control the orientation of liquid crystal molecules. The plane wave expansion method and the finite element method are employed to theoretically analyze bandgap characteristics, polarization characteristics, energy fraction and material absorption loss. The results show that this fiber structure can be used as tunable terahertz polarization controller.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Stochastic Collocation Method (SCM), a prevailing uncertainty analysis method, has been successfully implemented in Electromagnetic Compatibility (EMC) simulation, especially in EMC commercial software. However, the “curse of dimensionality” problem (dimensionality means the number of uncertain variables) limits the application of the SCM. This paper proposes a novel sparse grid strategy in order to improve the computational efficiency of the SCM, especially in high dimensionality case. In the proposed strategy, it is revealed that the number of the collocation points is in proportion to the dimensionality. By simulating two shielding effectiveness analysis examples in CST software, the feasibility of the proposed method can be presented clearly, with the help of the Feature Selective Validation method.

A compact optical fiber refractive index (RI) sensor based on a tiny S fiber taper (SFT) cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The SFT can excite and recouple the cladding modes, and hence, it produces modal interference, which is sensitive to surrounding refractive index. Due to the reflection of FBG, RI measurement can be realized by monitoring the peak power change of the reflective FBG spectrum. The experimental result shows that the RI sensitivity of the sensor can be achieved as high as 366.69 dB/RIU ranging from 1.3330 to 1.3988. Moreover, this sensor possesses the temperature-insensitive characteristic. The corresponding RI measurement error is about $3.136\times 10^{-5}$ RIU/°C in the temperature range of 30 °C–70 °C.

A terahertz photo-thermoelectric (PTE) detector is proposed by integrating the metamaterial absorber with a metal thermocouple. The incident terahertz wave that is absorbed by the metamaterial absorber changes into heat, then the heat changes into electricity by using the metal thermocouple. The absorption performances, photo-thermal, and PTE conversion characteristics are investigated by the full vector finite element method. Simulation results show that the device can achieve near-perfect absorption in 1 THz, and exhibits a responsivity and noise equivalent power of 35 mV/W and 6.6 × 10−6 W/Hz 1∕2 , respectively. Meanwhile, with the advantages of room-temperature workability, wide-angle, high responsivity, simple structure, and easy integration, the device has potential applications in terahertz photoelectric detection, sensing, and imaging.

The illumination uniformity of incubators used for growing edible mushrooms has an important influence on the accuracy of extracted light formula. To design a light emitting diode (LED) array with uniform illumination, we study the influence of number of LEDs, luminous half angle and the position on the two-dimensional plane by using the genetic algorithm. Numerical results show that the illumination uniformity of optimized LED array can reach up to 97%, which is superior to those of traditional rectangular, elliptical and triangular LED arrays. Finally, simulation results obtained from TracePro software verify that accuracy of numerical calculations.

Uncertainty analysis is widely used in today's electromagnetic compatibility simulations in order to include the variation and tolerance caused by realistic nonidealities. However, previous research has neglected to investigate the validity evaluation of uncertainty analysis results. In this paper, a novel validity evaluation method, named mean equivalent area method (MEAM), is proposed to quantify the difference between the reference data and the simulation results, particularly for validity evaluation of the uncertainty analysis results in computational electromagnetics. Comparing with other existing works or confirmed conclusion in published references, the performance of MEAM is presented. Furthermore, in order to improve both efficiency and accuracy of the uncertainty analysis method (Monte–Carlo method or generalized polynomial chaos method), a scheme based on MEAM is presented to examine whether the uncertainty analysis method has reached convergence. Finally, the selection of the reference data and the limitation of MEAM are illustrated in detail in Section VI .

We investigate the optical scattering properties of gold nanocup with different orientation and fractional height by full vector finite element method. All of the scattering cross section, the distribution of electric field intensity, and the ability of directional light scattering are simulated, respectively. It is demonstrated that the scattering cross section of Au nanocup is a superposition of scattering spectrum of a transverse mode and an axial mode. The wavelength and the intensity of the maximum value of the scattering cross section increase initially then reduce with the fractional height increasing for transverse mode, while they increase monotonously with the fractional height increasing for axial mode. Furthermore, the calculation results show that the ability of redirecting incident light of Au nanocup mainly depends on the transverse mode. And the deflected angle of scattering increases with the fractional height of Au nanocup decreasing. These results indicate that Au nanocup has a promising application in the planar plasmon devices.

An electromagnetically induced transparency (EIT) in metamaterial resonator with two bright modes and one dark mode at the terahertz (THz) band is numerically and experimentally demonstrated. Different from two kinds of the traditional passive modulations, our design can realize the passive modulation of EIT phenomenon by adding another bright mode resonator. Simulated and experimental results show that the transmission peak varies for incident THz waves with different polarization directions due to its asymmetric structure, which provides a novel way to realize high efficiency switch and modulation.

Uncertainty analysis methods are widely used in today’s Electromagnetic Compatibility (EMC) simulations in order to take account of the non-ideality and unpredictability in reality and improve the reliability of simulation results. The Stochastic Galerkin Method (SGM) and the Stochastic Collocation Method (SCM), both based on the generalized Polynomial Chaos (gPC) expansion theory, have become two prevailing types of uncertainty analysis methods thanks to their high accuracy and high computational efficiency. This paper, by using the Feature Selective Validation (FSV) method, presents the quantitative accuracy comparison between the foregoing two methods, with the commonly used Monte Carlo Method (MCM) used as the comparison reference. This paper also introduces SCM into the CST software simulation as an example of performing uncertainty analysis. The advantages and limitations of SGM and SCM are discussed in detail in this paper. Finally, the strategy of how to choose between SGM, SCM, and MCM under different situations is proposed in the conclusion section.

A multi-direction bending sensor based on the 18-core photonic crystal fiber (PCF) is demonstrated in this paper. The design of the sensor is discussed theoretically and experimentally. The PCF serves as the laser gain medium and the sensing medium simultaneously in the fiber laser sensor. The operating wavelength of the proposed PCF laser sensor is about 1032.32 nm. A CMOS image capture system is used to acquire the distribution of supermodes in the PCF laser. Based on the normalized intensity distribution of supermodes, six directions can be measured. The sensor also shows the ability to measure bending radius within 0.11 m. Then, the thermal effects of the bending sensor have been analyzed and the sensing system shows a low temperature crosstalk.

In the design stage of electromagnetic device, the way to handle the uncertainty of design parameters has attracted wide attention. Monte Carlo Method works well when dealing with uncertainties but it consumes too much time and computing resource. This paper proposes a computationally efficient way to achieve robustness based on Stochastic Collocation Method and TEAM 22 is used as a verification example. It is demonstrated that the approach combining Stochastic Collocation Method and genetic algorithm provides high computational efficiency without losing accuracy comparing with Monte Carlo Method.

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). By designing this scheme, we showed that the structural, electronic, and optical properties are excited for lasing at 1550 nm. The preliminary results show that the device can produce a good light spot shape convenient for direct coupling with the waveguide and single-mode light emission. The laser luminous power can reach up to 2.32 mW at a wavelength of 1550 nm with a 300-mA current. Moreover, at room temperature (300 K), the laser can maintain maximum light power and an ideal wavelength (1550 nm). Thus, this study provides a novel approach to reliable, efficient electrically pumped silicon-based lasers.

The Stieltjes Process is introduced to construct orthogonal polynomials for the random variables with arbitrary probability distributions in the application of the generalized Polynomial Chaos. The accuracy and efficiency of the proposed method are verified by comparing the results with that of the Monte Carlo method. It is demonstrated that the polynomial chaos method achieves the same accuracy as the Monte Carlo method but higher efficiency when it is used to assess the influence of randomness of input parameters in the crosstalk simulation.

A low loss broadband terahertz (THz) polarization splitter with a compact and simple structure has been proposed, which is based on the mode coupling between two porous fibers with orthogonally oriented cross section microstructures. The dispersion curves of the porous fibers are adjusted by the index converse matching coupling method. An interlacing stacking technique using polymer tubes and rods is presented for the fabrication of the proposed high-birefringence porous fiber. The characteristics of single porous fibers have been analyzed in detail. In addition, the dual-porous fiber-based polarization splitter has such desirable merits as ultrashort splitting length, low loss, and broad operation band. Compared with other dual-core PCF polarization splitters, this scheme possesses simpler structure, ease of fabrication, and better practical feasibility. This letter would be also of significance for the design of related broadband operation THz devices.

A terahertz bandpass filter with the sandwich structure consisting of thermally tunable vanadium dioxide (VO2) thin film, silica substrate and subwavelength rectangular Cu hole arrays is designed and theoretically analyzed. The results show that the transmittance of the filter can be actively tuned by controlling the temperature of VO2, the narrow band terahertz (THz) waves with the transmittance from 85.2% to 10.5% can be well selected at the frequency of 1.25 THz when the temperature changes from 50 °C to 80 °C, and the maximum modulation depth of this terahertz bandpass filter can achieve 74.7%.

A random porous fiber for transporting terahertz (THz) waves is proposed in this paper. The fiber, which to the best of our knowledge has not been investigated previously, has its core composed by randomly distributed air holes. A numerical study was carried out near 1 THz, showing that the new fiber possesses some improved fiber properties compared to the regular periodic porous fiber: the power fraction confined in the core is higher, the dispersion becomes lower, and more importantly a flatter dispersion curve appears within the frequency range of 0.8 THz to 1.4 THz.

The spectral behaviors of pulsed Hermite–cosh–Gaussian (HChG) beams focused by an aperture lens are studied. The propagation equation for the power spectra of pulsed HChG beams focused by an aperture lens is derived and used to study the spectral anomalies of pulsed HChG beams in the focused field. Numerical results are given to illustrate the dependence of spectral anomalies behavior on the pulse parameter and truncation parameter. The potential applications of spectral anomalies of ultrashort pulsed beams in information encoding and information transmission are considered.

Starting from the Huygens–Fresnel diffraction integral, the analytical expressions for the power spectra of diffracted pulsed Hermite-cosh-Gaussian (HChG) in dispersive media are derived and used to study the spectral anomalies of pulsed HChG. Numerical results are given to illustrate the dependence of spectral anomalies behavior on the decentered parameter, truncation parameter and dispersive property of the medium. The potential applications of spectral anomalies of ultrashort pulsed beams in the information encoding and information transmission are considered.

The coupling between the line defect and point defect in a two-dimensional photonic crystal is studied by using plane wave expansion method and finite difference time domain method. Based on the analysis, we propose a novel tunable terahertz narrow-band filter. Simulation results on the defect modes and output spectra show that the photonic crystal that consists of two line defects and one point defect can act as a tunable filter with narrow bandwidth of 0.02 THz under the control of an external electric field.

Starting from the Huygens–Fresnel diffraction integral, the analytical expression for the power spectrum of diffracted pulsed Bessel beams in a dispersive media is derived and used to study the spectral anomalies of pulsed Bessel beams in the far field. Numerical results are given to illustrate the dependence of the anomalous spectral behavior on the pulse parameters, aperture parameter and dispersive properties of the medium. It is shown that, near phase singularities, anomalous spectral behavior may take place. The potential applications of spectral anomalies of ultrashort pulsed beams in information encoding and information transmission are considered.