Slot Waveguide Research Articles

Nonvolatile multilevel adjustable optical switch based on plasmonic slot waveguide and GST segmented structure

Optical computing has gradually demonstrated its efficiency in handling increasingly complex computational demands, attracting widespread attention. Optical switches can effectively control and modulate optical signals, providing flexibility and efficiency for optical computing systems. However, traditional optical switches face performance issues such as power consumption, switching speed, and compactness, severely limiting the implementation of large-scale photonic integrated circuits and optical neural networks. This paper proposes an innovative design structure for a non-volatile multi-level adjustable optical switch by combining a plasmonic slot waveguide with segmented phase-change materials. Modulation of waveguide light transmission is achieved by adjusting the phase state of Ge2Sb2Te5(GST). At a wavelength of 1550 nm, a low insertion loss of 0.5dB has been achieved, with approximately an 85% difference in optical transmittance between amorphous state (aGST) and crystalline state (cGST). The high transmittance difference contributes to achieving a wide range of weight variations and supports precise weight updates. Based on this design, we successfully implemented a handwritten digit recognition task with an accuracy of 95%, laying the foundation for future more efficient memory computing neural morphic networks.

A P/X Dual-Band Co-Aperture Array with Dual-Polarized Antenna Based on Forest Biomass Measurement Applications

In this paper, a co-aperture dual-polarized antenna array is proposed. The frequency band covers the P-band (0.4–0.7 GHz) and the X-band (9.3–9.9 GHz). The P-band array is designed in the form of an all-metal Vivaldi, while minimizing the impact of the P-band antenna array structure on the X-band electrical performance. The final profile design for the dual-band antenna structure is only 0.12 λ0 (λ0 corresponds to the wavelength of 0.4 GHz). The X-band design adopts the miniaturized waveguide slot structure, which can be well embedded in the P-band array structure. In order to verify the feasibility of the scheme, prototype processing and testing were carried out, and the test results are consistent with the simulation results. The active VSWRs of the overall design are less than 2.0. Additionally, the dual-band antenna array has favorable radiation performance in each frequency band. It can be used in forest biomass measurements and other interferometric applications.

Ultra-low loss compact active TM mode pass polarizer using phase change material in silicon waveguide

An active low-loss transverse magnetic (TM) pass polarizer, based on the phase change material (Ge2Sb2Te5), is proposed. The proposed polarizer is based on silicon-on-insulator technology that consists of a silicon waveguide that incorporates a thin layer of Si3N4 placed in-between GST. Enhancing the interaction between light and GST is achieved by strategically placing a double-layer GST adjacent to the slot waveguide. The polarizer’s tunability, on the other hand, depends on the shift in the refractive index (RI) of GST as it transitions between its crystalline and amorphous phases. By optimizing the structure, the polarizer exhibits negligible loss for both modes in the amorphous phase, and with the change of phase to crystalline, the loss of TE mode is more than 8 dB. In contrast, the loss of TM is less than 0.05 dB with a high ER of 21.82 dB, propagation length of 79.89 µm and Figure of merit reaches up to 108 at 1550 nm. Due to the combination of these performance parameters, the suggested active TM pass polarizer is an appealing and effective device for various photonic applications. In addition, the fabrication technique of the proposed active TM pass polarizer is explained.

Design of the Monopulse Feeding Network for a Slotted Waveguide Array on an Annular Disk

Design of a monopulse feeding network including a compact power distribution network and a monopulse comparator for a dual polarization slotted waveguide array fabricated on an annular disk is presented in this paper. As the slotted waveguide array is arranged on an annular disk, the feeding network is more complicated than that of a regular array such as a rectangular array. The design details of some key waveguide components, such as the compact assembly of H-plane T-junctions and E-plane elbows used to connect power distribution networks and radiation waveguides, are provided. Quasiplanar magic tees are designed and used to construct the compact sum and difference comparator. The antenna system contains two comparators, which are used to generate sum and difference beams for horizontal polarization and vertical polarization, respectively. Finally, the monopulse slotted waveguide array antenna is divided into two modules, a comparator module and an antenna module (including power distribution network), and fabricated with the layered processing and bonding process. The comparator module is measured using a network analyzer to verify its amplitude-frequency characteristics and phase-frequency characteristics. Screwing the comparator module and the antenna module together, a monopulse slotted waveguide array antenna is obtained, and the sum beam and difference beam characteristics of the antenna are measured in a microwave chamber and presented.

ANN-based estimation of dispersion characteristics of slotted photonic crystal waveguides

ANN-based estimation of dispersion characteristics of slotted photonic crystal waveguides

Planar slotted waveguide antenna array for monopulse radar

In monopulse radar, along with mirror and lens antennas, slotted waveguide antenna arrays (SWA) are often used, especially in those cases when it is required to have a flat non-protruding shape and compact dimensions. The design and manufacturing of such antennas have specialties associated with the use of non-standard feeding systems of radiating waveguides, which are considered in this paper as the example of creation of a flat SWA intended for use in a monopulse search and tracking radar. The aim of the article is calculating and modeling a slotted waveguide antenna array based on a hollow metal waveguide with a given level of side lobes and main lobe width of the radiation pattern. The developed SWA contains a radiating and feeding part. The radiating part, with 24 linear resonant waveguide-slot antennas with longitudinal slots on the wide wall of the waveguide, is divided into two subarrays to realize the monopulse mode. Each subarray is fed from the feeding waveguide through slanted slots cut in the wide wall of the waveguide. The antenna design calculation has been carried out in the MathCad, and the modeling has been performed in CAD Ansys HFSS. The energy method has been used to calculate the coordinates of the longitudinal slots on the wide wall of the radiating waveguide as well as the inclined slots on the wide wall of the feeding one. The calculated radiation patterns of the developed antenna array in the E- and H-planes in sum and difference modes have been shown. The paper outlines the methodology for designing a monopulse antenna system using a SWA. The system forms a beam directed perpendicular to the antenna plane. During the design process, the slotted waveguide antenna array based on a hollow waveguide has been modeled and researched to obtain the required characteristics specified in the technical requirements. The proposed approach can be applied to practical antenna design for monopulse radars.

Efficiency enhancement of a circularly polarised slotted waveguide antenna array for Sub-THz applications

Efficiency enhancement of a circularly polarised slotted waveguide antenna array for Sub-THz applications

Generation of OAM beams with quasi omnidirectional pattern using simple slotted waveguide array

Theory and design aspects of the Slotted Waveguide Antenna (SWA) array for the simultaneous generation of Orbital Angular Momentum (OAM) modes are proposed in this paper. The proposed method is a novel approach to OAM generation that uses a simple feeding scheme and has better performance, especially in terms of mode purity. Due to its all-metallic structure, the high-power OAM beams with first-order modes (+1&-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ +1 \\, \\& \\,-1$$\\end{document}) can be generated simultaneously along the propagation axis but in opposite directions, which improves the coverage and makes the proposed SWA be used in applications like radar target detection by mounting it on a mechanically rotating platform. The proposed theory is verified by the electromagnetic (EM) simulations, followed by the experimental verification done on the laboratory prototype. The near-field characteristics of the proposed antenna confirm the generation of first-order OAM beams with high mode purity. The far-field characteristics show the high gain and quasi-omnidirectional radiation pattern. Transmission of high-power OAM beams with good far-field characteristics makes the proposed antenna mitigate the issues of long-range OAM communication to a certain extent. However, the proposed antenna can be served well in strategic applications where the mostly high-power microwave is involved.

Research into the Impact of Phase Shifter Failures on the Characteristics of Slotted Waveguide Array Antenna

Introduction. Currently, the impact of phase shifter (PS) failures on the characteristics of phased antenna arrays, slotted waveguide array antenna (SWAA) in particular, represents a significant problem. A review of publications shows that insufficient attention has been paid to PS failures.Aim. To investigate the characteristics of a SWAA in the event of PS failures, when their phase takes a value equal to zero instead of the required value.Materials and methods. The methods of statistical modeling methods were used to study the impact of failures on SWA characteristics. Calculations were carried using the Mathcad 15 software package.Results. An algorithm for statistical modeling of the impact of PS failures on SWAA characteristics is proposed. A relationship that connects the radiation pattern with the volume of the statistical sample and the number of failed PSs is given. The malfunctions of emitters from 5 to 35 out of 50 elements were studied. Changes in the following characteristics were obtained: standard deviation – from 0.064 to 0.18, radiation pattern width – from 8 to 18 %, the level of side lobes – from 13 to 59 %, radiation power – from 0.9 to 0.3.Conclusion. The results obtained can be used in radio-electronic systems with antenna arrays at the stage of their development. Future work will address PS failures with phases being established randomly and with random values, as well as the case of PS failures where power does not pass into the emitter. Another important direction concerns compensation of distortions resulting from failures of antenna elements.

Matched dielectric slot waveguide as an all-dielectric terahertz magnetic dipole.

We observe that the modal field distribution of a dielectric slot waveguide closely resembles a magnetic dipole antenna. Such an aperture distribution traditionally demands metals, making it ill-suited to high frequencies due to excessive ohmic loss. By terminating a dielectric slot waveguide with a matched free-space interface, a compact all-dielectric radiating magnetic dipole is realized. In this way, we introduce general-purpose dipole antennas, which have long been a mainstay of RF and microwave ranges, into the realm of light wave photonic integrated circuits. The existence of the desired magnetic dipole aperture distribution is experimentally confirmed in the terahertz range, at ∼275 GHz, and good matching is evident in the ∼-25 dB reflection level. This is the electrically smallest radiator to ever be incorporated into an all-dielectric waveguiding platform.

Dielectric Waveguide-Based Sensors with Enhanced Evanescent Field: Unveiling the Dynamic Interaction with the Ambient Medium for Biosensing and Gas-Sensing Applications—A Review

Photonic sensors utilize light–matter interaction to detect physical parameters accurately and efficiently. They exploit the interaction between photons and matter, with light propagating through an optical waveguide, creating an evanescent field beyond its surface. This field interacts with the surrounding medium, enabling the sensitive detection of changes in the refractive index or nearby substances. By modulating light properties like intensity, wavelength, or phase, these sensors detect target substances or environmental changes. Advancements in this technology enhance sensitivity, selectivity, and miniaturization, making photonic sensors invaluable across industries. Their ability to facilitate sensitive, non-intrusive, and remote monitoring fosters the development of smart, connected systems. This overview delves into the material platforms and waveguide structures crucial for developing highly sensitive photonic devices tailored for gas and biosensing applications. It is emphasized that both the material platform and waveguide geometry significantly impact the sensitivity of these devices. For instance, utilizing a slot waveguide geometry on silicon-on-insulator substrates not only enhances sensitivity but also reduces the device’s footprint. This configuration proves particularly promising for applications in biosensing and gas sensing due to its superior performance characteristics.

Optimization and Comparative Analysis of Rectangular and Slot Waveguide based Symmetric Ring and Racetrack Resonators for SoI Photonic Integrated Filters

Optimization and Comparative Analysis of Rectangular and Slot Waveguide based Symmetric Ring and Racetrack Resonators for SoI Photonic Integrated Filters

Model of slot antenna for MPECVD of carbon nanostructure

A model of a slotted waveguide antenna for microwave plasma enhanced chemical vapor deposition (MPECVD) of carbon nanostructures at low pressure is developed. The performance of two slot applicator for the production of dense plasma in the working gas (argon) at a frequency of 2.45 GHz is investigated by EM field simulator. Results show that dimensions of the symmetrical slots (length l ≤ λg/2, width of d = 6-10 mm) and optimized angle (φ=32° with respect to the waveguide central line) have a strong influence on the impedance matching of the waveguide to the dielectric window and plasma column (1.5 < SWR < 2.5), and on the radiation efficiency. The dielectric plate and plasma column density were taken into account in the model in the optimisation of the dimensions of the slots. The mode structure of standing surface waves in the plasma column is investigated at three values of plasma density and results for the radial (n=1) and azimuthal wave numbers (m=3, 4, 5) are in agreement with experimental results.

A new SOI sensor design for detecting cancer using hybrid waveguide with higher sensitivity than both strip and slot waveguides

A new highly accurate optical biomedical sensor is proposed for cancer detection characterized by high sensitivity, small footprint, low cost, and low limit of detection. The sensor is based on double-ring resonators made of silicon on insulator. The type of the waveguide is critical in determining the sensor performance. To compromise the advantages and disadvantages of strip and slot waveguides, a mixed design of both has been introduced in literature at the expense of increased footprint compared to traditional sensors. Indeed, almost 27-fold footprint increase is required to improve the sensitivity by only one third of that of slot waveguide’s sensitivity. In this paper, we introduce a new design that keeps the same footprint of traditional sensors, while achieving high sensitivity. This sensitivity depends on the resonance wavelength shift due to different refractive indices of the biosample. It has the value 109.8 nm/RIU compared to 55.57 nm/RIU and 129.621 nm/RIU for strip and slot waveguides, respectively. The hybrid waveguide quality factor is 537.7 while the quality factors of the strip and the slot waveguides are 627.99 and 380.76, respectively. In addition, the new design achieves the minimum limit of detection (0.0255) when compared to that of traditional designs. Furthermore, a new method of detection is proposed with the same design, providing a higher sensitivity over both traditional waveguide types with a value of 15.3, compared to 13.2 and 11.5 for strip and slot waveguides, respectively. In this method, the sensitivity relies on various values of output transmitted light at the same wavelength due to altering the biocell refractive index. The biosensor output equation is developed. In addition, the relationship between the supermodes and the sensitivity is determined at variance conditions. It is found that there is an inverse relation between them.

Local-field engineering in slot waveguide for fabricating on-chip Bragg grating filters with high reflectivity across a flat broadband.

On-chip Bragg gratings with high reflectivities have been found to have widespread applications in filters, resonators, and semiconductor lasers. However, achieving strong Bragg reflections with flat response across a broad bandwidth on the popular 220 nm silicon-on-insulator (SOI) platform still remains a challenge. In this paper, such a high performance device is proposed and fabricated, which is based on a slot waveguide with gratings etched on the inner sidewalls of the slot. By manipulating the local field in the slot region using a chirped and tapered grating-based mode transition, the device achieves a flat response with ultra-high reflection and low transmission for the TE mode across a broad operating bandwidth. Leveraging the ultra-high birefringence of the SOI waveguide, the device functions both as a TE slot waveguide reflector and a TM pass polarizer. Simulation results demonstrate that the device exhibits an ultra-high rejection of more than 50 dB and a reflectivity exceeding 0.99 for the TE mode across a 91 nm wavelength range, while maintaining a high transmittance of larger than 0.98 for the TM mode. Experimental results validate that the device performance is consistent with the simulation results. A fabricated device based on such a gratings exhibits a low insertion loss (<0.8 dB) and high polarization extinction ratio (>30 dB) over 100 nm bandwidth (1484 nm-1584 nm), demonstrating that the performance of the present design is competitive with that of the state-of-the-art SOI Bragg gratings.

A Method for Low Sidelobe Substrate-Integrated Waveguide Slot Antenna Design Applied for Millimeter-Wave Radars

With the development of millimeter-wave radar systems, substrate-integrated waveguide (SIW) slot antennas have been widely used. This paper presents a computational approach for calculating the equivalent normalized admittance of slot in low sidelobe SIW longitudinal slot antennas. In contrast to the existing methods, this method takes into account the impact of the N-slots coupling on the admittance. Through this method, fitting functions for resonant length and conductance are obtained, which describe the relationship between the resonant length, resonant conductance, and offset of slots. Moreover, based on the two fitting functions, a low sidelobe SIW longitudinal slot linear antenna is designed for millimeter-wave radar applications at 77 GHz. This antenna consists of a transition from the standard WR-12 waveguide to the SIW and a set of radiating slots. The simulation results indicate an impedance bandwidth of 4.8% and a gain of 13.2 dBi. The sidelobe level in the H-plane is below −28 dB, which meets the desired specifications and confirms the accuracy of the presented method.

Slot waveguide enhanced asymmetric photonic crystal nanofiber cavity for fiber-coupled single photons

We report a slot waveguide-enhanced asymmetric photonic crystal optical nanofiber (ONF) cavity to realize cavity quantum electrodynamics. We show that the device can strongly enhance the spontaneous emission of a single quantum emitter leading to a Purcell factor as high as 106 and enables single-photon coupling efficiency as high as 86% into fiber-guided modes. The introduction of the slot enhances the Purcell factor by six times as compared to the ONF cavity structure without slot, and the asymmetric cavity design enables unidirectional coupling of single photons. The cavity is designed to minimize the losses leading to a scattering-limited Q-factor and one-pass loss estimated to be 6388 and 1.2%, respectively. This fiber-coupled single-photon device may open advanced possibilities and applications for quantum information processing.

Enabling Wide Bandwidth in Substrate-Integrated Waveguide Slot Antennas by Using Low-Index Metamaterials

Enabling Wide Bandwidth in Substrate-Integrated Waveguide Slot Antennas by Using Low-Index Metamaterials

High gain narrow wall standing wave slotted waveguide antenna with flanges

ABSTRACT In this study, narrow (edge) wall standing wave slotted waveguide antenna design is proposed. This antenna operates at 2.812 GHz in S frequency band. Also, the design equations and slot characterization method are given in this study. This antenna is designed with two flanges to shape the elevation pattern and to increase the antenna gain. This antenna provides low cross polarization without using any polarizer or any other structure. The designed antenna is suitable for high gain and high-power applications. The performance of the proposed design is examined with simulations and verified with measurements.

Self-Calibration Technique and Permittivity Measurement Using a Slotted Rectangular Waveguide

Self-Calibration Technique and Permittivity Measurement Using a Slotted Rectangular Waveguide