Bandwidth Performance Research Articles

Ultra-compact silicon nitride dual-polarization mode converter for visible light demonstrated on a thinned 320 nm silicon wafer

A dual-polarization higher-order mode converter is proposed for visible light, which operates within the (400–700) nm range, to enhance data capacity in on-chip visible light communication systems. The proposed structure is optimized at wavelengths of 410 nm, 560 nm, and 660 nm to cover the entire visible spectrum. These three optimized designs, in particular, have an intrinsic property wherein they can be optimized to simultaneously convert both polarized fundamental (TE0) and fundamental (TM0) modes to the second higher-order (TE2) and (TM2) modes, providing significant advantages for hybrid multiplexing systems like PDM-MDM and PDM-WDM schemes. The mode converters are constructed on a silicon nitride waveguide. This waveguide is etched and filled with silicon dioxide material to create two dielectric substrips, followed by an additional rectangle shape etched using the same process into the propagating waveguide. This alteration enhances insertion loss and diminishes crosstalk to the fundamental mode. The devices achieve a broad operating bandwidth of approximately 100 nm while maintaining a compact footprint of only 1µm×1.754µm for the entire device at the center wavelength of 560 nm. Upon optimizing the suggested structure, a TE0-to-TE2 mode converter with a modal conversion efficiency of 94% is designed at the wavelength of 410 nm. The insertion loss is 0.6025 dB, and the crosstalk with the transverse electric fundamental mode TE0 is 35 dB. The reported devices feature a straightforward structure with low insertion loss and minimal crosstalk.

Dual-channel asymmetric absorption-transmission properties based on plasma metastructures-photonic crystals

In this paper, a kind of plasma metastructures-photonic crystals (PMPC) structure is proposed to investigate the absorption and transmission properties of electromagnetic waves (EWs) incident from opposite directions. The results show that the PMPC can achieve a dual-channel asymmetric absorption-transmission (AAT) phenomenon. At an operating bandwidth (OB) of 2.15∼2.85 GHz, EWs are absorbed in the forward incidence and transmitted in the backward case, and a relative bandwidth (RB) with forward absorption above 0.9 is 28.0%. On the contrary, at an OB of 7.07∼7.67 GHz, EWs can be transmitted in the forward propagation and absorbed in the backward case with a RB of 8.1%. Moreover, the effects of parameters such as applied magnetic field, incident angle, and tilt angle on AAT performance are investigated separately. The proposed dual-channel tunable AAT will further extend the application of asymmetric devices in the fields of optical communication and optical transmission.

Electrochemical Switching of Electromagnetism by Hierarchical Disorder Tailored Atomic Scale Polarization.

High-frequency electronic response governs a broad spectrum of electromagnetic applications from radiation protection, and signal compatibility, to energy recovery. Despite various efforts to manage electric conductivity, dynamic control over dielectric polarization for real-time electromagnetic modulation remains a notable challenge. Herein, an electrochemical lithiation-driven hierarchical disordering strategy is demonstrated for actively modulating electromagnetic properties. The controllable formation and diffusion of coherent interfaces and cation vacancies tailor the coupling of atomic electric field and thus the locally polarized domains, which leads to the reversible electromagnetic transparency/absorption switching with a tunable range of -0.8--20.4 dB for the reflection loss and a broad operation bandwidth of 4.6 GHz. Compared to traditional methods of heteroatomic doping, hydrogenation, mechanical deformation, and phase transition, the electrochemical strategy shows a larger regulation scope of dielectric permittivity with the maximum increase ratios of 260% and 1950% for real and imaginary parts, respectively. This enables the construction of various device architectures including the adaptive window and pixelated metasurface. The results offer opportunities to achieve intelligent electromagnetic devices and pave an avenue to rejuvenate various electromagnetic functions of semiconductive oxides.

Polarization-sensitive mechanically-tunable microwave filter using metallic photonic crystals

A tunable, polarization-sensitive microwave filter based on a reconfigurable dual-layered two-dimensional metallic photonic crystal is presented. The filter consists of a metallic plate with periodic holes and metal pillars which are anchored in a substrate material. The diameter of the pillars is smaller than that of the holes and the lateral position of the pillars with respect to the holes is tunable. We study the transmission of the device for linearly polarized electromagnetic radiation, which is polarized parallel and perpendicular to the displacement of the movable membrane, respectively. The tuning range spans from 20.18 GHz to 26.58 GHz for perpendicular polarization and from 20.18 GHz to 18.42 GHz for parallel polarization. The 3 dB operation bandwidth varies between 3.82 GHz and 6.44 GHz for perpendicular polarization and between 3.42 GHz and 3.82 GHz for parallel polarization. Experimental data are in good agreement with finite element method (FEM) simulations. The proposed structure is scalable to other frequency ranges such as terahertz frequencies.

Extending the spectral operation of multimode and polarization-independent power splitters through subwavelength nanotechnology

Power splitters play a crucial role in virtually all photonic circuits, enabling precise control of on-chip signal distribution. However, state-of-the-art solutions typically present trade-offs in terms of loss, bandwidth, and fabrication robustness, especially when targeting multimode operation. Here, we present a novel multimode 3-dB power splitter based on a symmetric Y-junction assisted by two regions of subwavelength grating metamaterials with different geometries. The proposed device demonstrates high-performance for multimode and dual-polarization operation with relaxed fabrication tolerances by leveraging the additional degrees of freedom offered by two distinct geometries of subwavelength metamaterials to control mode evolution. Our design achieves, to the best of our knowledge, the widest operational bandwidth reported to date for a nanophotonic multimode silicon power splitter. Simulations for a standard 220-nm-thick silicon-on-insulator platform predict minimal excess loss (< 0.2 dB) for the fundamental and the first-order transverse-electric modes over an ultra-broad 700 nm bandwidth (1300 – 2000 nm). For the fundamental transverse–magnetic mode, losses are less than 0.3 dB in the 1300 – 1800 nm range. Experimental measurements validate these predictions in the 1430 – 1630 nm wavelength range, demonstrating losses < 0.4 dB for all three modes, even in the presence of fabrication deviations of up to ± 10 nm. We believe that this device is suitable for the implementation of advanced photonic applications requiring high–-performance distribution of optical signals, such as programmable photonics, multi-target spectroscopy and quantum key distribution.

Achromatic Full Stokes Polarimetry Metasurface for Full-Color Polarization Imaging in the Visible Range.

Metasurfaces provide an ultrathin platform for compact, real-time polarimetry. However, their applications in polychromatic scenes are restricted by narrow operating bandwidths that causes spectral information loss. Here, we demonstrate full-color polarization imaging using an achromatic polarimeter consisting of four polarization-dependent metalenses. Leveraging an intelligent design scheme, we achieve effective arbitrary phase compensation and multiobjective matching with a limited database. This system provides broadband achromaticity across wavelengths from 450 to 650 nm, resulting in a relative bandwidth of approximately 0.364 for full Stokes imaging. Experimental reconstruction errors for wavelengths of 450, 550, and 650 nm are 7.5%, 5.9%, and 3.8%, respectively. Performance is evaluated based on both achromatic bandwidth and crosstalk, with our design achieving three times the performance of the current state-of-the-art. The full-color, full-polarization imaging capability of the device is further validated with a customized object. The proposed scheme advances polarization imaging for practical applications.

A compact coupling-fed omnidirectional wideband filtering antenna with high selectivity

ABSTRACT This paper presents a compact coupling-fed omnidirectional wideband filtering antenna with high selectivity for modern wireless communication systems. The antenna integrates a coupling-fed driven patch with a symmetrical printed Г-shaped dipole, facilitating wideband performance and high selectivity through multiple coupling paths. Coupling-fed structure introduces radiation nulls (RNs), achieving an operating bandwidth of 54.5% for |S11| ≤ −10 dB and out-of-band suppression of −9 dB without requiring additional circuits. Simulations and experiments validate the antenna’s performance, demonstrating multiple resonant frequencies and consistent omnidirectional radiation patterns. Compared to traditional designs, it offers superior bandwidth and selectivity, making it suitable for integration into planar RF circuits in applications such as Wi-Fi 6, 5 G, and radar systems.

Ultra‐wide Band Antipodal Vivaldi Antenna Using Metasurface Lens for Gain and Front‐To‐Back Ratio (FBR) Improvement

AbstractThis paper addresses the limited gain of conventional Antipodal Vivaldi Antenna (AVA) at higher frequencies. We propose a novel Metamaterial Lens Vivaldi Antenna (MLVA) design that overcomes this limitation by integrating an exponentially tapered antenna lens and a strategically placed Near Zero Refractive Index (NRZI) metamaterial lattice. The MLVA achieves exceptional wideband performance with a −3 dB gain bandwidth exceeding 148.6% from 3.7 to 25 GHz. The result demonstrates a peak realized gain of 11.8 dBi at 11.2 GHz, compared to 9.1 dBi conventional AVA, especially beyond 5 GHz. The compact MLVA design measures only 120 × 78 × 1.524 mm3 (1.48 × 0.96 × 0.0188λ03) λ0 where free‐space wavelength is the lowest frequency and is fabricated on RO4350 B substrate with a 50‐Ω SMA connector. Key features of the design include exponential flaring, and trapezoidal lens geometries chosen for their inherent ability to effectively collimate and direct the spherical wavefront. The incorporation of a dielectric lens and metasurface further enhances gain and Front‐to‐Back Ratio (FBR) by directing the majority of energy in the end‐fire direction. Experimental results validate the effectiveness of the proposed design, confirming simulation predictions. These outstanding characteristics make the MLVA a promising candidate for diverse wireless communication and radar applications demanding high data rates across a broad frequency range.

All-optical platform for ultrasound transmission matrix measurements

Piezoelectric ultrasound transducers are constrained by size, bandwidth, and angular response, limiting their ability to fully characterize the acoustic properties of objects. In this study, we introduce a novel modular all-optical platform for ultrasound generation and detection to overcome these limitations, demonstrating wideband operation (&amp;gt;50 MHz), omnidirectional response, and high signal fidelity. Ultrasound generation is performed via the optoacoustic effect by illuminating an optically absorbing coating with spatially modulated pulsed light, and ultrasound detection is carried out using a silicon-photonic acoustic detector. By illuminating patterns that span a basis and scanning the detector, the full transmission matrix is measured, consisting of the acoustic waveforms for all the transmitter–receiver pairs in the measurement geometry. Our method is experimentally demonstrated in transmission mode for beam steering, beam focusing, and imaging, achieving excellent agreement with the theory.

A 28 GHz balun‐first LNA with db‐linear 32 db gain range for 5 G applications

AbstractThis letter presents a 28 GHz balun‐first low noise amplifier (LNA) featuring a wide dB‐linear variable gain range. The architecture of LNA includes three‐stage cascode amplifiers. An integrated balun at the input stage provides RF ESD protection and converts a single‐ended signal to a differential one (S‐to‐D). A transformer‐based dual‐resonant matching network is designed and analyzed to achieve wideband performance. To realize a continuous dB‐linear variable gain range and consistent input/output matching, gain control is implemented in the second stage using a 5‐bit digital‐to‐analog converter (DAC) for a 32 dB gain range. The DAC can generate a nonlinear analog voltage to control the gate of the common‐gate transistor in the second cascode stage, inversely compensating for the nonlinear gain variations of the cascode amplifier. The LNA is fabricated in 65‐nm CMOS process with a core size of 0.154 mm². Measurement results exhibit a maximum gain of 33.5 dB and a minimum noise figure (NF) of 3.65 dB with a 3‐dB bandwidth of 23–29.5 GHz. The measured variable gain range is approximately 32 dB across 32 different gain states, with a linear gain step of ~1 dB per state and an IP1dB ranging from −6.5 dBm to −35.25 dBm. The power consumption is 35.4–48 mW from a 1.2 V supply voltage.

A novel output window for dual-band gyrotron amplifier

Abstract As a high-frequency, high-power, and high-bandwidth microwave source, the gyrotron amplifier has good application prospects in the aerospace field. The microwave window is of great significance for the high-frequency characteristics, power capacity, lifespan, and reliability of the gyrotron amplifier. This paper introduces a novel double-disk sapphire output window, which has excellent mechanical strength, high-temperature resistance, and high power capacity. The transmission coefficient S21 of TE01 mode is greater than −1 dB in 8.29 GHz∼9.73 GHz, and the S21 of TE02 mode is greater than −1 dB in 16.33 GHz −17.8 GHz, which can ensure wide bandwidth operation of high microwave transmission in X and Ku bands. It solves the problem of using one port to achieve microwave output in two bands for dual-band gyrotron amplifiers.

Gain enhancement of compact CPW‐Fed ultra‐wideband antenna using an FSS reflector

AbstractIn this paper, an enhancement gain of compact CPW‐Fed antenna using a single layer frequency selective surfaces (FSSs) reflector for ultra‐wideband (UWB) applications is presented. A hexagonal CPW‐Fed antenna with a size of 30 × 30 mm2 is realized to provide a UWB bandwidth operation. In this study, a novel design of an FSS unit cell with reduction and a small size of 8 × 8 mm2 is proposed. It allows one to achieve a UWB band‐stop response between 3 and 11.5 GHz. The FSS reflector has 7 × 7 units with a total size of 56 × 56 mm2. This reflector is placed below the antenna at a distance of 20 mm. The main objective of this contribution is to improve the gain level of the antenna, where the proposed antenna achieves an improvement of realized gain of 6.2 dBi with increasing from 2.2 to 8.4 dBi. The antenna became more directive after the integration of the FSS reflector with a directional radiation pattern. The numerical and experimental results are in good concordance with the simulated one. This study is performed in terms of voltage standing wave ratio, radiation pattern, realized gain, and radiation efficiency.

A Compact and Flexible Monopole Antenna with Controllable Bandwidth

In this paper, a compact antenna with flexible and controllable bandwidth characteristics is proposed. To ensure wide coverage along with an omnidirectional radiation pattern, a monopole structure was utilized as the primary radiating element of the proposed antenna. The monopole was fed using a coplanar waveguide technique to achieve a single-layer design. To alter the operating bandwidth, defined by a reflection coefficient of less than -10 dB, a single stub was directly connected to the feeding transmission line. By controlling the stub's length, matching performance in the high-frequency range was found to undergo significant degradation, indicating that the operating bandwidth could be controlled. Furthermore, for validation, two antenna prototypes were fabricated and measured under different circumstances. In the unbending mode, the design without the stub achieved a wideband of 51.6%, while the other design with the stub exhibited a narrower band of about 19.6%. Additionally, the antennas worked efficiently when operating in bending mode. It is also worth noting that the antenna gain and radiation pattern remained stable across the entire operating bandwidth.

Wideband and Low-Profile Array of Tightly Coupled Dipole Subarrays

This letter introduces a novel wideband, low profile, tightly coupled dipole subarray for wireless communication systems. The proposed subarray, composed of 3 × 3 unit elements, offers a planar structure with high aperture efficiency. The unit element is a bow-tie-shaped tightly coupled dipole antenna covered by a frequency-selective surface for wideband operation. Using power dividers with quarter-wave transformers, the proposed subarray achieved an impressive impedance-matching bandwidth of 28.6–41.6 GHz (37.8%). This wideband performance was maintained in a 4 × 4 array configuration as well. The antenna’s low-profile design (0.08λc) and high aperture efficiency (77.2%) set it apart from existing wideband patch array antennas, making it a promising candidate for future wireless communication applications.

Enhancing C+L-band transmission performance through OSNR flatting and link damage recovery algorithms

The rapid growth of data-intensive services has driven the need for high-capacity optical networks. C+L band optical communication systems have emerged as a potential solution by extending the operational bandwidth. However, the wider spectrum introduces significant stimulated Raman scattering (SRS) effects that impact signal power profile, Kerr nonlinearity, and amplified spontaneous emission (ASE) noise. To address these challenges, this paper proposes an optical power control strategy designed to achieve a flat optical signal-to-noise ratio (OSNR) across all transmitted channels, which is particularly effective in mitigating SRS effects in C+L band systems. Furthermore, a link damage recovery algorithm is developed to ensure system robustness against localized fiber degradations. Extensive simulations are conducted to compare the performance of the proposed strategy with the conventional flat launch power approach under single-span and multi-span transmission scenarios. The results demonstrate that the proposed strategy achieves a higher minimum generalized signal-to-noise ratio (GSNR), exhibits stronger resilience to link damage across a wide range of transmission conditions.

Physical analysis of high refractive index metamaterial-based radiation aggregation engineering of planar dipole antenna for gain enhancement of mm-wave applications

A metamaterial-incorporated high-gain and broadband dipole antenna is proposed for 5G mm-wave applications. The designed high refractive index metamaterial (HRIM) properties are presented in detail with supporting results. The proposed dipole antenna achieved broadband features, and the antenna gain increased significantly by incorporating HRIM in the electromagnetic (EM) wave propagation path. Besides, the EM wave aggregation engineering of utilizing the HRIM on the dipole antenna is analyzed using the electric field, magnetic field, and power flow distributions. Both conventional and HRIM-based dipole antenna (HRIMDA) were fabricated on thin (0.254 mm) Rogers RT5880 substrate material with a low dielectric constant of 2.2, where the noticeable gain enhancement by HRIM is observed. The measured results show the operational bandwidth (BW) from 23 to 38 GHz frequency, and the highest gain of 9.5 dBi is accomplished at 35 GHz frequency. Finally, a four-element MIMO configuration is numerically and experimentally analyzed where the isolation of the two conjugated MIMO elements is < − 20 dB. The MIMO parameters like envelop correlation coefficient (ECC) < 1 × 10–3 and diversity gain (DG) value of > 9.9 were also achieved. Hence, the proposed HRIM base dipole antenna is a potential candidate for 5G mm-wave applications.

Active friction-regulated inertia impact piezoelectric actuator

In inertia impact piezoelectric actuators, the phenomenon of high-frequency drive-induced back-stepping poses a significant limitation to their overall performance. The ultra-fast response time of the piezoelectric stack enables the resolution of this issue. This paper introduces an inertia impact piezoelectric actuator operating under a novel Dual-Stack Motion Mode (DCMM), diverging from the traditional operation in the Single-Stack Motion Mode (STMM) that involves a solitary piezoelectric stack (PES) for active friction control. A comprehensive description of the actuator's structure and its operational principles under DCMM is provided. By constructing and experimentally evaluating the actuator using a controlled variable approach, a comparative analysis of performance between DCMM and STMM across various scenarios including different inertial mass blocks, driving voltages, frequencies, and load conditions was conducted. The experimental results indicate that DCMM significantly enhances the actuator's output performance, achieving a maximum speed of 1142.79 μm/s and a stable single-step displacement of 0.5 μm. The actuator features a simple yet effective structure and driving mechanism, allowing for multiple driving modes through the assembly of different inertial masses, thereby providing a substantial competitive advantage in output performance. The feasibility of using DCMM to improve actuator performance is corroborated by both theoretical and experimental studies. The ultra-fast response of the piezoelectric stacks expands the operational bandwidth of the actuator, achieving a seamless integration of speed and precision.

Enhanced vibration energy harvesting from coupled pendulums through inertial amplifiers

Abstract Achieving higher power output across a broader frequency spectrum presents a significant challenge for vibration energy harvesters aimed at powering low-powered devices from ambient sources. This study introduces the novel concept of employing inertial amplifiers to couple mistuned pendulum electromagnetic harvesters for enhanced energy harvesting performance. A mathematical model elucidating the inertial amplifier mechanism is developed, and analytical results are compared against conventional uncoupled harvesters. Experimental studies demonstrated up to 1.8 times higher power output and a 2-fold increase in operational frequency bandwidth compared to uncoupled harvesters when employing inertial amplifier coupling. The proposed inertially coupled harvester design offers a powerful solution to significantly improve energy transduction levels and extend the viable frequency range, enabling efficient scavenging of ambient vibrations for powering wireless sensors and low-power electronics.

Wide-angle reflection control with a reflective digital coding metasurface for 5G communication systems

Abstract Metasurfaces have attracted widespread attention in recent years due to their powerful electromagnetic wave manipulation capabilities. This paper proposes and validates a single-polarized, angle-adjustable reflective digital coding metasurface. Each unit cell achieves independent reflection phase control by loading a PIN diode for on-off switching. The unit’s design and coding scheme are carefully optimized to ensure the performance of the proposed reconfigurable metasurface. As a validation, a prototype consisting of 16×16 elements is fabricated and measured, with a control signal provided by a field-programmable gate array controller. Experimental results demonstrate angle control of up to ±60° in the frequency range of 3.4 GHz–3.6 GHz, a peak gain of 24.9 dBi in a single channel, and gain exceeding 10 dBi across a 200 MHz operational bandwidth. Furthermore, the performance is validated in a communication system, yielding positive results. The proposed reflective digital coding metasurface contributes to the advancement of reconfigurable intelligent surfaces and holds promise for widespread adoption in various communication scenarios.

Design of highly efficient filtering power amplifier with a wideband response for sub-6 GHz 5G applications

This paper presents the design of a filtering power amplifier (PA) with extra-high power-efficiency and wide bandwidth. To accomplish this, a novel approach is adopted by utilizing a wideband bandpass filter (BPF) as the output matching network (OMN) for the PA. The BPF compromises two paths, where each path consisting of two identical coupled lines that are interconnected to form a ring structure. The suggested configuration eliminates the need for a conventional OMN by integrating the input port of the filter with the drain node of the transistor, resulting in reduced size and losses and improved amplifier performance. The filter concept is illustrated using coupling matrix synthesis. A proof-of-concept filtering PA has been designed using a commercially available 10 W GaN HEMT. This amplifier was designed to operate in the frequency range of 3.0–5.0 GHz, yielding a fractional bandwidth of 50 %. According to achieved results, the drain efficiency and output power are 43.8–70.5 % and 40.2–41.8 dBm, respectively. As a result, the suggested filtering PA demonstrates significant performance in terms of filter bandwidth response and power amplification. Additionally, the proposed filtering PA has a broad operational bandwidth of 3.0–5.0 GHz, which covers the 5G New Radio (NR) n77 (3.3–4.2 GHz), n78 (3.3–3.8 GHz), and n79 (4.4–5.0 GHz) frequency bands.