Elliptical Waveguide Research Articles

CPW fed optically transparent ultrawideband fractal MIMO terahertz antenna with meshed ground plane

Abstract An optically transparent UWB antenna element and its two-element pattern diversity MIMO configurations are presented in this paper. Three iterations of the quarter elliptical coplanar waveguide ground plane, rectangular microstrip feedline, and octagonal annular rings make up the antenna element. By metal meshing the ground planes and loading the radiator with several octagonal slots, the optical transparency is improved. It has a maximal achieved gain of 6.78 dBi and operates with steady radiation characteristics over the frequency spectrum of 4.52–28.64 THz (145.48%). The dimensions of the antenna element are 18 × 20.5 μm2. A metallic stub is positioned between two identical antenna components that are positioned orthogonally to one another to create a two-element pattern diversity MIMO antenna arrangement. The MIMO antenna is 20.5 × 42.5 μm2 in total. Its impedance bandwidth is 23.72 THz for port 2 and 22.68 THz for port 1. Using a rectangular stub results in an intraport isolation of >19 dB. Between the two ports, the planes in the radiation patterns have switched places. The diversity performance characteristics, which are considerably below the permissible limitations, are as follows: ECC > 0.01, CCL < 0.3 b/s/Hz, DG ∼ 10, TARC < 0 dB, MEG ∼ −3 dB, and 1≤VSWR_MIMO≤2. Compared to previously published structures, the suggested antenna structures have the advantages of smaller dimensions, a larger bandwidth, and improved optical transparency.

A Wideband Dual-Circularly Polarized Inverted Quad-Ridged Elliptical Waveguide Horn Antenna

A Wideband Dual-Circularly Polarized Inverted Quad-Ridged Elliptical Waveguide Horn Antenna

Design of millimeter wave broadband polarization reconfigurable horn antenna based on elliptical waveguide polarizer

AbstractA broadband polarized reconfigurable horn antenna for K‐band and Ka‐band is designed using a circular polarizer in the form of an elliptical waveguide and a circular waveguide flange based on a gap structure. The designed noncontact circular waveguide flange with gap structure can switch the antenna excitation signal to different modes of electromagnetic waves by mechanical rotation. When excited by different modes of electromagnetic waves, the designed elliptical waveguide circular polarizer can switch between linear polarization, left‐handed circular polarization, and right‐handed circular polarization. The antenna is analyzed in principle, modeled and simulated, and processed by three‐dimensional printing process. The measured results show that S11 ≤ −15dB, axial ratio ≤ 3 dB, gain ≥14 dBi in 37.8% relative bandwidth range (22.5–33 GHz). The proposed antenna is broadband, multipolar, and reconfigurable, which makes it have broad application prospects in the field of satellite communication and millimeter‐wave communication.

Normalized frequency for noncircular dielectric waveguides

AbstractThis paper points out that the commonly used normalized frequency for noncircular dielectric waveguides, which is based on the semiminor axis, causes the cross‐sectional area to vary with the cross‐sectional shape. Consequently, the shape effects described with the conventional normalized frequency are not due to the shape alone but the combined effects of the shape and area. Our numerical results show that the area effect is greater than the shape effect. An improved definition of normalized frequency based on an equivalent radius is proposed in this paper. Conversion formulas to convert from the conventional normalized frequency to the proposed normalized frequency are provided for elliptical and rectangular waveguides. Our numerical results show that the shape effects described by the proposed normalized frequency are free from the area effect. Consequently, the proposed normalized frequency is more accurate than the conventional normalized frequency in describing the shape effect of noncircular dielectric waveguides.

Analysis of hollow elliptical waveguide with metamaterial cladding

Analysis of hollow elliptical waveguide with metamaterial cladding

An online tunable TE11 dual-circular polarizer applied for modern high-power radar system

Circular polarizers have essential applications in modern radar and communication systems. However, an online tunable wideband dual-circular polarizer with a power capability of more than 150 kW in the Ku band has not been reported yet, and it has recently become a fundamental problem for developing some high-power radar systems. This paper has designed an overmoded waveguide operating in the TE11 mode with a non-contact cutting-off choke to imply a high power capability. A high-precision stepping motor is used to control the rotation of an elliptical waveguide remotely, and then, the left-hand and right-hand circular polarizations can be switched online. The dual-circular polarizer has been fitted on a 150 kW gyro-TWT high-power test system, and the experimental results show a tremendous high-power capability. The microwave leakage caused by the non-contact gap is reduced to less than −35 dB. The polarization bandwidth exceeds 2.5 GHz in the Ku band, and the axial ratio is better than 1.3 dB. This design concept provides a reference for future high-power radar systems.

Nanomaterials in Nanophotonics Structure for Performing All-Optical 2 × 1 Multiplexer Based on Elliptical IMI-Plasmonic Waveguides

In this study, an all-optical multiplexer (Mux) based on elliptical insulator-metal-insulator (IMI) plasmonic waveguides is designed. The area of the proposed structure is very small (400 nm × 400 nm) which operates at a wavelength of 1,550 nm. The developed device utilizes constructive and destructive interferences between the input signals and the selector signal. This structure is less complex and has lower loss compared to the previous works. Transmission (T), contrast ratio (CR), modulation depth (MD), insertion loss (IL), and contrast loss (CL) are the five parameters that describe the performance of the plasmonic Mux. The transmission threshold between logic 0 and logic 1 is 0.5. Moreover, the maximum transmission efficiency of the device is 163%. Moreover, based on the MD value of 95.09%, the dimensions of the proposed structure are excellent and optimal. The proposed plasmonic Mux structure contributes substantially to developing an all-optical arithmetic logic unit (ALU) and all-optical signal processing nanocircuits. The finite element method (FEM) simulates the proposed plasmonic multiplexer with COMSOL Multiphysics 5.4 software.

Analysis and Application of the Electromagnetic Wave Propagation, Fields, and Dispersion Relation in an Elliptical Chiro Plasma Waveguide Immersed in Magnetized Plasma

AbstractThis research proposes and investigates an elliptical waveguide filled with chiro plasma as its core and magnetized plasma as its clad region. The clad region is in the constant infinite magnetic field, and its direction is the same as the wave propagation in the chiro plasma elliptical waveguide. The electromagnetic wave propagation in the considered waveguide is studied. The expressions for electromagnetic field components in the chiro plasma core and magnetized plasma cladding are derived. The dispersion relations for the hybrid modes are calculated considering appropriate boundary conditions at the chiro plasma and magnetized plasma interface. The behavior of the energy flux and the dispersion curves are numerically and graphically studied. It is seen that the magnitude of the power density decreases with the increase of the cyclotron frequency and it increases with the increase of the plasma frequency and supports power flow in the backward direction for the considered mode. Furthermore, it is shown higher values of the chirality parameter cause the magnitude of the power flux to increase in the backward direction.

Vortex solitons in large-scale waveguide arrays with adjustable discrete rotational symmetry

We consider vortex solitons in large-scale arrays composed of N elliptical waveguides placed on a ring, which can be fabricated using fs-laser writing technique in transparent nonlinear dielectrics. By introducing variable twist angles between longer axes of neighboring elliptical waveguides on a ring, we create circular arrays with adjustable discrete rotational symmetry ranging from CN to C1, when the number of waveguides N on the ring remains fixed. This allows to consider the impact of discrete rotational symmetry on the properties of available vortex solitons without changing the number of guiding channels in the structure, and to predict how exactly splitting of higher-order phase singularities into sets of charge-1 singularities occurs in vortex states, when they are forbidden by the discrete rotational symmetry of the structure that imposes the restrictions on the maximal possible vortex charge. It is found that separation between split charge-1 phase singularities in such higher-order vortex states increases with increase of the order of solution. We also study linear spectra of such arrays and show how variation of their discrete rotational symmetry affects linear eigenmodes, whose combinations can give rise to vortex modes. We also show that variation of discrete rotational symmetry in arrays with fixed number of guiding channels N has strong impact on stability of vortex solitons. Thus, only higher-charge vortex solitons are stable in such large-scale arrays and the number of stable states typically decreases with decrease of the order of discrete rotational symmetry of the structure at fixed N.

1.55-μm Sidewall Grating DFB Lasers Integrated With a Waveguide Crossing for an Optical Beam Forming Network

By using asymmetric twin-waveguide technology, a 1.55-μm sidewall grating distributed feedback laser monolithically integrated with a passive waveguide crossing was for the first time demonstrated for an optical beam forming network, which needs only one metalorganic vapor-phase epitaxy step. The distributed feedback laser with uncoated facets presents a side-mode suppression ratio of >44 dB and a low 3-dB linewidth of 68 kHz. An elliptical parabolic taper waveguide crossing had a theoretical crosstalk suppression ratio of 40 dB, while the measured cross-talk suppression ratio was at least 20 dB.

Electromagnetic wave propagation in a chiroplasma-filled elliptical waveguide, bounded by a perfect electromagnetic conductor.

This work presents electromagnetic wave propagation in the elliptical waveguides filled with chiroplasma core and an outer perfect electromagnetic conductor boundary. The electromagnetic fields were theoretically examined. The hybrid modes' dispersion relations and power flux density were calculated considering appropriate boundary conditions, and their behaviors were numerically and graphically studied. The effects of the plasma frequency, the cyclotron frequency, the chirality parameter, and the perfect electromagnetic conductor admittance parameter were investigated for the cutoff frequency. Different modes were considered, and the dispersion relation was plotted and studied for each case. It was shown that the cutoff frequency changes with the change of various parameters such as the plasma and cyclotron frequencies, the chirality parameter, and the perfect electromagnetic conductor admittance parameter. In addition, it was shown that for the considered mode, when the plasma or cyclotron frequencies increase, the values of correspond cutoff frequencies have higher or lower values, respectively. Higher values of the perfect electromagnetic conductor admittance parameter or the chirality admittance parameter yield lower or higher cutoff frequencies of the modes, respectively.

An elliptical beam-tunnel sine waveguide slow wave structure for G-band elliptical beam traveling wave tube

In order to improve the performance of sine waveguide (SW) traveling wave tube (TWT), an elliptical beam-tunnel sine waveguide (EBTSW) slow wave structure (SWS) is proposed. EBTSW-SWS not only has high interaction impedance in a relatively wide frequency band but also has an elliptical beam-tunnel. The simulation results of high-frequency characteristics show that, under the same dispersion, the passband of EBTSW-SWS increases by 30% compared to the SW-SWS, and the average interaction impedance of EBTSW-SWS is higher than that of SW-SWS in almost the whole passband. Moreover, the particle-in-cell (PIC) simulation results reveal that under the operating voltage of 20.8 kV and beam current of 150 mA, EBTSW-TWT can provide more than 70 W of saturated output power in the frequency range of 200-260 GHz, reaching the maximum power of 151 W at 220 GHz with the maximum electronic efficiency of 4.85%.

Ultra-deep Subwavelength Confinement Palladium-Based Elliptical Cylinder Plasmonic Waveguide in the Near-Infrared Range

Ultra-deep Subwavelength Confinement Palladium-Based Elliptical Cylinder Plasmonic Waveguide in the Near-Infrared Range

Topological Bound Modes With Orbital Angular Momentum in Optical Waveguide Arrays

Coupled optical waveguide arrays, in which the wave tunnelling dynamics resembles that of electrons in crystals, have been utilized as a versatile tool to demonstrate topological phenomena. So far, the study of topological phases in waveguide arrays mostly focused on the supermodes constituted by the fundamental modes of single waveguide while the high-order modes with orbital angular momentum (OAM) are rarely considered. Here the topological bound modes are investigated in a zigzag chain composed of evanescently coupled waveguides that support OAM modes. We show the topological propagation is aroused by OAM without discovering any bound modes generated by fundamental modes. The reason lies in the coupling of OAM modes between adjacent waveguides naturally gives rise to synthetical gauge fields, significantly different from fundamental modes. Furthermore, we study the coupling mechanism of elliptical waveguides and show the orientation angle of ellipses serves as gauge fields as well, which provides an additional degree of freedom to control topological bound modes.

Non-Hermitian coupling of orbital angular momentum modes in optical waveguides

We investigate the optical coupling of orbital angular momentum (OAM) modes in a multimode waveguide assisted by a lossy single-mode waveguide. By utilizing coupled mode theory, we show that the coupling coefficients between two OAM modes with opposite rotation directions become imaginary-valued in cylinder waveguides, which further gives rise to polarization-locked wave dynamics. Any injections with different polarizations finally evolve into linear polarization (LP) modes, as the output modes are synthetized by antisymmetric supermodes of two OAM modes. In addition, non-Hermitian asymmetric couplings are induced in elliptical waveguides, which stem from the interaction between synthetical gauge fields and dissipation. By increasing the ellipticity of waveguides, the degree of asymmetric coupling increases, and the system experiences a phase transition, which can be reflected from propagation characteristics of OAM modes. The study provides a promising approach for controlling modal coupling of OAM modes and may find potential applications in OAM generation and polarization conversion.

Potentials and Fields of Space-Charge Waves in the Coaxial Elliptical Waveguide Consisting of An Annular Plasma in the Presence of An Axial Magnetic Field

Potentials and Fields of Space-Charge Waves in the Coaxial Elliptical Waveguide Consisting of An Annular Plasma in the Presence of An Axial Magnetic Field

Transient nuclear inversion by x-ray free electron laser in a tapered x-ray waveguide

By restricting the spatial energy transmission of an electromagnetic wave, dielectric waveguides transmit light over long distances at sustained intensity. Waveguides have been used in the microwave and optical range to maintain strong signal intensities in connection with lasers, but guiding of intense short-wavelength radiation such as x-rays has proven more cumbersome. Here we investigate theoretically how tapered x-ray waveguides can focus and guide radiation from x-ray free electron lasers. Elliptical waveguides using a cladding material with high atomic number such as platinum can maintain an x-ray intensity up to three orders of magnitude larger than in free space. This feature can be used to significantly enhance resonant interactions of x-rays, for instance driving nuclear transitions up to transient nuclear population inversion. This could be the first breakthrough in nuclear state population control. Our results anticipate the important role of tapered x-ray waveguides in the emerging field of x-ray quantum optics with nuclear transitions.

Synthesis of Highly Oversized TE₀₁ to TE₁₁ Mode Converter Based on Elliptical Waveguide

Highly oversized mode converters are the critical devices for high power millimeter-wave transmission systems, characterizing high power capacity and low loss. In order to improve the conversion efficiency from TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> to TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode, the mode coupling mechanism of oversized elliptical waveguides is explored, and an optimal ellipticity interval to obtain the high conversion efficiency is deduced by analyzing the mode coupling capacity. Considering that ellipticity can affect the power capacity, breakdown thresholds of different operating modes in elliptical waveguides are studied. Based on the analyses, a synthesis method to design the elliptical mode converter integrating the mode conversion efficiency and the power capacity is proposed. A highly oversized mode converter working in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band is designed, and the simulation results demonstrate that the mode converter achieves the high conversion efficiency over 95% in a relative bandwidth of 19.6%. In order to validate the design, a prototype of the mode converter is fabricated, and the high purity of outputted TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode is verified by the measurement. The oversized mode converter designed by the proposed synthesis method features high efficiency, broad bandwidth, and high power capacity, enabling its full utilization of the potential of gyrotron traveling-wave tubes (gyro-TWTs).

Elliptical and circular annular solid electron beam for excitation of hybrid modes in the plasma combined circular and elliptical waveguides

For two new configurations presented and by considering annular solid electron beam with background plasma the growth rates of the hybrid modes and the dispersion relation of electromagnetic waves propagating are studied. The interaction of elliptical and circular annular solid electron beams with plasma is investigated that it occurs microwave radiation generation dependent of configuration dimensions. The structures are including metallic elliptical(circular) waveguide with elliptical(circular) dielectric cladding and a core having a circular(elliptical) dielectric rod in center that it is surround by circular(elliptical)annular plasma and a circular(elliptical)annular relativistic electron beam is injected in to plasma. The electromagnetic fields components in each of regions in the considered configurations are calculated. By applying the boundary conditions dispersion relation and operating frequency are obtained. Furthermore for another case that it is applied an infinite magnetic field to considered structures,the problem is investigated. Numerical computations are made and results are graphically presented.

Plasmonic sensor realized on metal-insulator-metal waveguide configuration for refractive index detection

In this work, a plasmonic sensor established on metal-insulator-metal waveguide configuration is proposed and numerically investigated for biosensing applications. The spectral and sensing characteristics of the device are examined via the two-dimensional finite element method. Sensitivity (Sbulk) and figure of merit (FOM) are two important parameters that are considered to determine the device performance. The Sbulk of the device is considered as a ratio between the change in resonance wavelength and change in the ambient refractive index. Whereas FOM is the ratio of Sbulk to full width at half maximum. The Sbulk and FOM offered by the device are ~825.7 nm/RIU and ~13.14, respectively. This work can provide a guideline for the realization of highly sensitive plasmonic sensing devices. Full Text: PDF ReferencesN.L. Kazanskiy, S.N. Khonina, M.A. Butt, "Plasmonic sensors based on Metal-insulator-metal waveguides for refractive index sensing applications: A brief review", Physica E: Low-dimensional systems and Nanostructures 117, 113798 (2020). CrossRef D. Xiang, W. Li, "MIM plasmonic waveguide splitter with tooth-shaped structures", Journal of Modern Optics 61, 222-226 (2014). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Ultra-short lossless plasmonic power splitter design based on metal–insulator–metal waveguide", Laser Physics 30, 016201 (2020). CrossRef J. Park, S. Lee, B. Lee, "Polarization Singularities in the Metal-Insulator-Metal Surface Plasmon Polariton Waveguide", IEEE Journal of Quantum Electronics 46, 1577-1581 (2010). CrossRef M. T. Hill, M. Marell, E. S. P. Leong, B. Smalbrugge, Y. Zhu, M. Sun, P. J. V. Veldhoven, E. J. Geluk, F. Karouta, Y-S. Oei, R. Notzel, C-Z. Ning, M. K. Smit, "Lasing in metal-insulator-metal sub-wavelength plasmonic waveguides", Optics Express 17, 11107-11112 (2009). CrossRef A. Udupi, S. K. Madhava, "Plasmonic Coupler and Multiplexer/Demultiplexer Based on Nano-Groove-Arrays", Plasmonics 16, 1685-1692 (2021). CrossRef Y-F. C. Chau, C-T. C. Chao, H-P. Chiang, "Ultra-broad bandgap metal-insulator-metal waveguide filter with symmetrical stubs and defects", Results in Physics 17, 103116 (2020). CrossRef H. Bahri, S. Mouetsi, A. Hocini, H.B. Salah, "A high sensitive sensor using MIM waveguide coupled with a rectangular cavity with Fano resonance", Optical and Quantum Electronics 53, 332 (2021). CrossRef S.N. Khonina, N.L. Kazanskiy, M.A. Butt, A. Kazmierczak, R. Piramidowicz, "Plasmonic sensor based on metal-insulator-metal waveguide square ring cavity filled with functional material for the detection of CO2 gas", Optics Express 29, 16584 (2021). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Plasmonics: A Necessity in the Field of Sensing-A Review (Invited)", Fiber and Integrated Optics 40, 14-47 (2021). CrossRef M.A. Butt, A. Kazmierczak, N.L. Kazanskiy, S.N. Khonina, "Metal-Insulator-Metal Waveguide-Based Racetrack Integrated Circular Cavity for Refractive Index Sensing Application", Electronics 10, 1419 (2021). CrossRef N.L. Kazanskiy, S.N. Khonina, M.A. Butt, A. Kazmierczak, R. Piramidowicz, "A Numerical Investigation of a Plasmonic Sensor Based on a Metal-Insulator-Metal Waveguide for Simultaneous Detection of Biological Analytes and Ambient Temperature", Nanomaterials 11, 2551 (2021). CrossRef I. Tathfif, A.A. Yaseer, K.S. Rashid, R.H. Sagor, "Metal-insulator-metal waveguide-based optical pressure sensor embedded with arrays of silver nanorods", Optics Express 29, 32365-32376 (2021). CrossRef P.D. Sia, "Overview of Drude-Lorentz type models and their applications", Nanoscale Syst. Math. Model. Theory Appl. 3, 1-13 (2014) CrossRef M.A. Butt, N.L. Kazanskiy, "Nanoblocks embedded in L-shaped nanocavity of a plasmonic sensor for best sensor performance", Optica Applicata LI, 109-120 (2021). CrossRef S. Khani, M. Hayati, "An ultra-high sensitive plasmonic refractive index sensor using an elliptical resonator and MIM waveguide", Superlattices and Microstructures 156, 106970 (2021). CrossRef F. Chen, J. Li, "Refractive index and temperature sensing based on defect resonator coupled with a MIM waveguide", Modern Physics Letters B 33, 1950017 (2019). CrossRef M. Rahmatiyar, M. Danaie, M. Afsahi, "Employment of cascaded coupled resonators for resolution enhancement in plasmonic refractive index sensors", Optical and Quantum Electronics 52, 153 (2020). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "A multichannel metallic dual nano-wall square split-ring resonator: design analysis and applications", Laser Physics Letters 16, 126201 (2019). CrossRef