TE Modes Research Articles

Three peak metamaterial broadband absorbing materials based on ZnSe-Cr-InAs stacked disk arrays.

Metamaterial absorbers show great potential in many scientific and technological applications by virtue of their sub-wavelength and easy-to-adjust structure, with bandwidth as an important standard to measure the performance of the absorbers. In this study, our team designed a new broadband absorber, which consists of an indium arsenide (InAs) disk at the top, a zinc selenide (ZnSe)-chromium (Cr) stacked disk in the middle and a metal film at the bottom. Simulation results show that the absorber has remarkable absorptivity properties in the mid-long infrared band. In a wavelength range of 5.71-16.01 μm, the average absorptivity is higher than 90%. In the band of 5.86-15.49 μm, the absorptivity is higher than 95%. By simulating the electromagnetic field diagram at each resonant frequency, the reason for high broadband absorptivity is obtained. We also constructed Poynting vector diagrams to further elucidate this phenomenon. Next, we analyzed the influence of different materials and structural parameters on absorptivity properties and tested spectral response at different polarization angles and oblique incidence of the light source in the TM and TE modes. When the source is normally incident, the absorber shows polarization insensitivity. When the angle is 40°, absorptivity is still high, indicating that the absorber also possesses angle insensitivity. The broadband absorber proposed by us has good prospects in infrared detection and thermal radiators.

Determination of temperature profile inside a PV module operating under specific conditions using a model coupling internal heating to optical absorption

In this study, the complex dynamics behind heat transfer within photovoltaic (PV) solar modules under spectral solar illumination are investigated. A new model coupling internal heating to optical absorption is derived from equations governing light-matter interaction throughout PV module multilayered structure. Reflection and transmission at each interface between two neighboring layers inside a PV module as well as absorption in each layer are taken into account. Dielectric properties of each interface are used to calculate its wavelength dependent reflectance and transmittance according TE and TM light polarization modes. Optical properties of each layer are utilized to determine its absorption coefficient and internal source of warming. Effects of incidence angle and light polarization modes on internal heat function are also analyzed. Heat equation is then solved in steady state limiting case and Temperature profiles inside a PV module under STC and NOCT conditions are determined.

Design of silicon slab waveguides based all‐optical logic gates

AbstractLogic gates are an indispensable part of digital circuits, and therefore such devices with fast operating speeds and simple designs are vital for all kinds of electronic applications. This paper proposes simple Y‐shaped designs of all‐optical AND, OR, and NOT logic gates in two dimensions that are operational in both TE and TM modes. These gates are designed using silicon slab waveguides, which makes them relatively easy to fabricate. The logic gates are designed, analyzed, and optimized at 1.55 µm using the finite difference time domain method. The truth tables of the proposed all‐optical logic gates are realized for every input case. The propagation delay time is determined to be of the order of femtoseconds (10−15 s), which is very fast compared to the response time of the currently reported all‐optical logic gates (10−9 ‐ 10−12 s).

ПОШИРЕННЯ ТЕРАГЕРЦОВИХ ВИХРОВИХ ЛАЗЕРНИХ ПУЧКІВ У ВІЛЬНОМУ ПРОСТОРІ

Subject and Purpose. Currently, numerous ideas and different methods have been in growth for generating vortex beams — areas of the circular motion of the electromagnetic wave energy flow around the so-called phase singularity points caused by a violation of the wave front topological structure. The purpose of this work is to obtain analytical expressions describing the nonparaxial diffraction of wave modes of the waveguide resonator of a terahertz laser during the wave mode interaction with a spiral phase plate. The resulting vortex beams are examined for their physical features in free space propagation. Methods and Methodology. The Rayleigh-Sommerfeld vector theory is adopted to consider the propagation of vortex laser beams generated by wave modes of the quasi-optical waveguide cavity when interacting with a spiral phase plate in different diffraction zones. Results. For the first time, analytical expressions have been obtained to describe the nonparaxial diffraction of wave modes of the waveguide resonator of a terahertz laser, when resonator modes interact with a spiral phase plate at different topological charges, n. The physical features of the resulting vortex beams were studied in their free space propagation. It has been shown that a spiral phase plate modifies the structure of the linearly polarized EH₁₁ mode so that the original (n=0) intensity profile with the maximum energy at the center turns at n=1 and 2 into a ring-like donut shape with an energy hole in the center. The azimuthally polarized TE₀₁ mode has originally (n=0) a ring-shaped intensity. At n=1, this configuration changes to have the maximum intensity in the center. At n=2, it becomes annular again. In the process, the spherical phase front of the beam of the linearly polarized EH₁₁ mode becomes spiral and have one singularity point on the axis, whereas the phase structure of the azimuthally polarized TE₀₁ mode gains a region with two phase singularity points off the axis. Conclusions. The results of the study can effectively facilitate information transfer in high-speed THz communication systems. They can provide a real platform to perform tasks related to tomography, exploring properties of materials, detecting astrophysical sources, which makes them very promising in modern technologies.

Highly efficient superradiant oscillator with front-extraction output in TE11 mode operating at low magnetic field

With a low guiding magnetic field, a highly efficient X-band coaxial superradiant relativistic backward wave oscillator (SR-RBWO) with a front-extraction cavity and a built-in mode converter is proposed in this paper. The coaxial structure is used to reduce the guiding magnetic field of the intense relativistic electron beam. To decrease the transmission loss of microwave power in the slow wave structure (SWS), a front-extraction cavity is introduced. The inner conductor of the coaxial SWS is hollowed out as the output waveguide, and then, the microwave is extracted by the front-extraction cavity and enters the hollow waveguide rather than re-enter the SWS to output. With this improvement, the power conversion factor K can be increased by 0.44 even more. Making use of the feature of longer SWSs of SR-RBWOs, a built-in mode converter is designed, which can convert the circular TM01 mode propagating in the output waveguide into the circular TE11 radiation mode that can be radiated into free space directly. Therefore, the length of the radiation system can be reduced significantly, which is beneficial to the miniaturization of the entire high-power microwave system. Particle-in-cell simulation demonstrates that with a diode voltage of 180 kV and a guiding magnetic field of 0.37 T, the output SR pulse with an average power of 1.00 GW corresponding to power conversion factor K = 1.8 can be obtained.

Tunable asymmetric square split ring resonator based triple band metamaterial absorber for wireless communication system

This article presents a triple band square split ring with double circular split ring resonator incident angle-insensitive perfect metamaterial absorber. The MMA unit cell was manufactured using a FR4 substrate that had dimensions of 8 mm by 8 mm. With the flexibility of on-design adjusting of the highest absorption frequencies, the suggested MA displays peak absorption of 99.67 %, 99.85 %, and 99.97 % at 2.52 GHz, 6.99 GHz, and 9.28 GHz, correspondingly. The tuning metallic two circular split rings and square split ring resonator provide the possibility of frequency modification throughout three distinct frequency ranges: the first frequency range extends from 2.45 GHz to 2.53 GHz, the second frequency range extends from 6.91 GHz to 7 GHz, and the third frequency range extends from 8.85 GHz to 10.32 GHz. Furthermore, the suggested MA displays near-zero absorption at an oblique incidence angle of up to 45° for both the TE as well as TM modes. The unit cell demonstrates single negative properties, such as an effective medium ratio (EMR) of 14.88 and a quality factor (Q factor) that is more than 30 for both the TM mode as well as the TE mode. An equivalent circuit successfully demonstrated its performance capability, which indicated that it would create an MMA of good quality when using ADS software. A comparison between the measured results of the suggested MMA and the simulated one reveals that there is a significant amount of a similarity between both of them. Because of its easy design within small dimension, wide angular stability, strong absorption, good EMR, and flexibility to frequency tuning is suitable for a wide range of wireless communication system, especially satellite applications like electromagnetic interference reduction, radar systems, imaging, and stealth technology.

Ultra-broadband on-chip mode size converter based on metasurface and taper on lithium-niobate-on-insulator platform

Mode size converter enables to match two waveguides with different mode sizes. It has already become an indispensable component in modern integrated photonics. Here, we propose a strategy for implementing an on-chip mode size converter consisted of a gradient geometry metasurface and two cascaded waveguide tapers on the lithium-niobate-on-insulator platform. The metasurface, which is formed by a series of length-graded silica nanostrips embedded into LN waveguide, functions as focusing of incident wave and exaltation of conversion efficiency. A mode size converter that enables to match a fundamental TE00 mode in a 10-μm-wide waveguide with that in a 0.8-μm-wide one was simulated to verify the feasibility of the strategy. We show that the device is not only compact with a length of 22.9 μm, but also shows an ultra-broad operation band as much as 1150 nm (from 1100 to 2250 nm), over which the conversion efficiency keeps >90 %. In addition, we show that the device has a good robustness to fabrication deviations. The strategy proposed here can be flexibly extended to other waveguide cross-section sizes and other guided modes.

Angular dependence of photonic band gap and omni-directional reflection in one-dimensional photonic crystal applied to a thermophotovoltaic device

In this work, we present a theoretical study and a numerical simulation on omnidirectional reflection in one-dimensional photonic crystal structures for a thermophotovoltaic device. The optical properties are determined using the transfer matrix method. The results show that the angular dependence of photonic bandgaps depends on refractive index contrast and, polarization. However, for both TE and TM polarization, a reflectivity peak with 100% reflectivity is observed. The Te/SiO2 structure is the one with the largest bandwidth of omnidirectional photonic band gap compared with the TiO2/SiO2 and Si/SiO2 structures. The results also show that by designing a giant birefringent optical the Brewster’s angle allows angle the control at any angle for both TE and TM mode.

Mode-Independent Optical Switch Based on Graphene-Polymer Hybrid Waveguides

Mode-division multiplexing (MDM) is a promising multiplexing technique to further improve the transmission capacity of optical communication and on-chip optical interconnection systems. Furthermore, the multimode optical switch is of great importance in the MDM system, since it makes the MDM system more flexible by directly switching multiple spatial signals simultaneously. In this paper, we proposed a mode-independent optical switch based on the graphene–polymer hybrid waveguide platform that could process the TE11, TE12, TE21 and TE22 modes in a few-mode waveguide. The presented switch is independent of the four guided modes, optimizing the buried position of graphene capacitors in the polymer waveguide to regulate the coplanar interaction between the graphene capacitors and spatial modes. The TE11, TE12, TE21 and TE22 modes can be regulated simultaneously by changing the chemical potential of graphene capacitors in a straight waveguide. Our presented switch can enable the independent management of the spatial modes to be more flexible and efficient and has wide application in the MDM transmission systems.

High-performance TM-pass polarizer based on anti-symmetric Bragg gratings.

We present an all-silicon transverse-magnetic-pass (TM-pass) polarizer based on anti-symmetric Bragg gratings. We obtain wide operation bandwidth and high polarization extinction ratio (PER) by maximizing the coupling between the forward TE0 mode and the backward TE1 mode through the reduction of the bridge element width. In the meantime, low insertion loss (IL) is acquired with long tapered structures and the exclusion of the center grating part. Experimental results indicate IL below 0.74 dB and PER over 40 dB covering the wavelength ranges of 1275-1360 nm and 1500-1523 nm, while the average IL within these ranges is as low as 0.27 dB. Additionally, simulation results suggest that the performance can be further improved by introducing chirp in the period of Bragg gratings, thus achieving IL < 0.11 dB and PER > 60 dB over a wide range of 280 nm (1290-1570 nm).

SLOW ELECTROMAGNETIC WAVES IN PLANAR THREE-COMPONENT WAVEGUIDE STRUCTURE WITH MU-NEGATIVE METAMATERIAL

This work is devoted to study of the dispersive properties of the slow electromagnetic waves that propagate along the planar waveguide structure that consists of semi-bounded plasma region, metamaterial slab and semibounded region of ordinary dielectric. It is studied the case when all media are homogeneous and isotropic. The dispersion properties, the phase and group velocities, as well as the electromagnetic field spatial structure of the eigen TE modes are studied in the frequency range where the metamaterial possess negative permeability.

Ultra-compact power splitting higher-order mode pass filter based on inverse design method

Higher-order mode pass filters and power splitters are indispensable components in mode division multiplexing (MDM) systems. In this work, we report a higher-order mode pass filter based on a 1 × 2 multimode interference (MMI), which can simultaneously perform power splitting. Our device is based on a direct-binary-search (DBS) algorithm, and blocked input TE0 mode while splits TE1 mode into two output waveguides with a 50:50 ratio. The final optimized device has an ultra-compact footprint of 2.88 × 2.4 μm2, while maintaining insertion loss <3.50 dB for TE1 mode and transmission extinction ratio between TE1 and TE0 mode >18.6 dB are achieved over the bandwidth of 1500 nm–1600 nm. The compact footprint and high performance of our optimized device make it a critical element for integration with other devices in future MDM systems.

A 330-GHz Radial Power Division/Combination Network Based on Circularly Polarized TE11 Mode

To compensate for severe mode interference and machining difficulties above the W-band of the traditional radial power combining scheme, a radial power division/combination network based on circularly polarized (CP) TE11 mode is designed. Firstly, the amplitude and phase distribution of the branches of a radial power divider under the excitation of CP mode are analyzed. The amplitudes of each branch are approximately equal, and the phase increases/decreases with equal differences. Therefore, a radial power divider with 16 branches based on a septum circular polarizer (SCP) is designed. An orthogonal cascade structure (OCS) and a parallel cascade structure (PCS) are proposed, and it is concluded that to obtain higher transmission efficiency, OCS and PCS should be used respectively when the phase or amplitude difference of SCP is worse. Finally, the power divider and a microstrip probe transition structure are cascaded back-to-back by using OCS, and the power division/combination network is obtained. Simulation results show that at 310-360 GHz, the amplitude difference of the branches of the power divider is less than ±0.35 dB; the combining efficiency of the power division/combination network is greater than 90%. This network has the advantages of single-mode operation, simple structure, and high combining efficiency. In addition, this article provides a feasible solution to the problem of depolarization loss caused by the cascade of SCPs.

Operation characteristics of a ten-cavity magnetron with TE11 mode extracted through compact diffraction output

We present the design of a ten-cavity magnetron extracting TE11 mode through compact diffraction output (DO). The effect of the DO length and the depth of the vane on the performance of the ten-cavity magnetron are investigated to design a compact diffraction structure. By adjusting the length of DO and the depth of the tapered cavities to provide a proper Qe, the output power and power conversion efficiency have been improved. Simulation results of the magnetron with compact DO (the length of the DO is about half an operation wavelength) show that the microwave power of 3.0 MW with a high conversion efficiency of 62% at 2.4 GHz is achieved under an applied voltage of 56 kV and a fixed axial magnetic field of 0.24 T. In addition, the length of the anode block is designed longer than the cathode to arrange the permanent magnet, which has been preliminary designed.

Two-Dimensional Magnetotelluric Forward Modeling in Space-wavenumber Mixed Domain

In magnetotelluric exploration, if you want to do 2D or 3D numerical modelling, what you need in the computational and memory requirements are potentially enormous. In order to get efficient and precise forward simulation results, we propose a new 2D numerical modelling method in space-wavenumber mixed domain. This method uses the one-dimensional Fourier transform in the horizontal directions, so the two-dimensional partial differential equations in the spatial domain can be transformed into a set of independent one-dimensional differential equations with different wave numbers. Then we can use the finite different method to solve the one-dimensional equations. In this article, the COMMEMI-2D1 model was used to verify the accuracy of the algorithm. We compare our results with the traditional finite different method in TE mode, indicating that the algorithm improves computational efficiency.

Silicon nano-bridge waveguide assisted polarizing beam splitter

A low-loss and wideband silicon polarizing beam splitter is demonstrated with the assistance of a nano-bridge waveguide. Transverse magnetic light can be coupled to the cross port through the nano-bridge waveguide, while the transverse electric light comes out mainly from the through port. The designed device has a coupling length of 19.6 µm, which can realize an extinction ratio of 32.43 dB for TM mode or 34.23 dB for TE mode at a 1565-nm wavelength. Compared with the conventional three-waveguide coupler structure, the proposed device is based on a resonant tunneling principle, which can help to effectively improve the fabrication tolerance. The device is fabricated with a commercial CMOS processing facility, which can achieve an extinction ratio of 23.07 dB for TM or 23.46 dB for TE mode with a low excess loss, and the extinction ratio of more than 10 dB can be realized in the wavelength range from 1525 to 1610 nm for both modes. The device performance can be further improved, which would facilitate its practical applications in commercial integrated optical circuits.

Holographic silver nanograting formation driven by TE0, TE1, and TE2 mode propagation in an AgCl slab Waveguide: Optical properties and analysis

Holographic silver nanogratings on the surface and within the volume, which have significant potential for data storage applications, are generated in silver chloride (AgCl) waveguides using a single laser beam exposure. This formation process leverages the interference between the polarized incident wave and the TEm modes propagating inside the AgCl waveguide. These plasmonic nanogratings are anisotropic nanostructures, demonstrating intriguing optical traits such as wavelength-specific linear dichroism and birefringence. The observed linear dichroism and birefringence in the holographic silver nanograting can modify the optical rotation and ellipticity of a probe beam traversing this anisotropic medium. Notably, volume holographic nanogratings function as complex nanogratings with a periodicity exceeding that of the incident wavelength. As a result, upon exposure, these complex nanogratings exhibit discernible light diffraction, while the surface holographic nanogratings do not show any diffraction pattern. Additionally, as the AgCl film thickness is increased and more complex nanogratings are formed within the AgCl waveguides, there is a noted reduction in the resulting birefringence.

Modelling of asymmetric channel plasmonic polariton waveguides

Channel plasmonic polariton (CPP) waveguides are a promising technology for integrated photonics. They offer several advantages over other plasmonic waveguides and are well-suited for various applications. In this research, a new design of asymmetric double-trenched CPP waveguide is suggested and examined. This design consists of two silicon trenches etched into a silicon dioxide substrate layer; with a gold layer sandwiched in between. The trenches are asymmetric, with one trench being wider than the other. This asymmetry creates a spatially varying surface plasmon polariton (SPP) field, which can guide light along the waveguide. The polarization characteristics of this proposed design are analyzed over a specific wavelength range (0.7 - 1.7 µm) to evaluate the mode confinement of the light within the structure. The design performance was optimized by changing the gold layer thickness and the dimensions of the lower trench. Different scenarios are examined to observe TE and TM-polarized modes’ behavior within the groove. A 1867.119 dB/µm suppression level at 0.92 µm wavelength is achieved which offers a small-size component for compact photonic logic gates, enabling the development of next-generation photonic devices.

Double elliptical resonator based quad-band incident angle and polarization angle insensitive metamaterial absorber for wireless applications

In this article, a double elliptical split ring resonator-based quad band metamaterial absorber (MMA) is demonstrated for applications in the microwave range. The resonator is made up of four squares outside split rings and two elliptical split rings positioned in the middle of the structure. The resonating patch is placed over an FR-4 dielectric layer with a thickness of 1.6 mm. The unit cell has an electrical size of 0.103λ0 × 0.103λ0, where λ0 is the wavelength determined at 2.576 GHz. The MMA shows maximum absorption of 99.83% at 2.576 GHz, 99.98% at 5.648 GHz, 99.56% at 8.32 GHz, and 99.15% at 13.456 GHz with TE mode. For TM mode, at 2.576 GHz, 5.632 GHz, 8.304 GHz, and 13.44 GHz, corresponding absorptions are 99.21%, 99.67%, 99.5%, and 99%, respectively. The MMA is polarisation and incidence angle (0° to 90°) insensitivity for both TM and TE modes. The unit cell provides single negative characteristics including an EMR (effective medium ratio) of 9.71 and a Q factor (quality factor) over 25. The proposed MMA provides high harvesting efficiencies of 92.87%, 76.9%, 94.12%, and 90.97% for frequencies of 2.57 GHz, 5.64 GHz, 8.32 GHz, and 13.45 GHz, correspondingly. The equivalent circuit is modeled to understand the resonance behavior of the MMA and the circuit parameters are determined and validated using Advanced Design Systems (ADS) software. The performance of the MMA is examined using the prototype of the array of the unit cells in an experimental setup. The experimental outcome provides a close similarity with simulation outcomes indicating the good performance of the MMA. The metamaterial absorber's high performance makes it suitable for many applications, such as RF energy harvesting applications, image technologies, stealth technologies, and radar systems as well as minimizing electromagnetic interference in satellites.

Dual-passband filter using dual-mode substrate-integrated waveguide resonator

ABSTRACTA novel dual-band bandpass filter (DB-BPF) based on SIW dual-mode resonant cavity is proposed in this study. This resonant cavity works in the degenerate mode TE102 mode and TE201 mode. The two modes of operation are coupled by opening a window between the resonant cavities, and the passband frequency of the DB-BPF is adjusted by controlling two degenerate modes. This filter works at 9 GHz and 9.5 GHz and has a 3-dB fractional bandwidth of 2.2% and 3.5% GHz, respectively, and has three transmission zeros (TZs) which improve out-of-band rejection and isolation between high-passband and low-passband. The return loss in the high-passband and low-passband is below 13 dB; the insertion loss of the high-passband and low-passband is 2.32 dB and 3.16 dB, respectively. The measured results agree well with the simulation results, which proves the feasibility of the design method.