Search Results (255)

This study presents a photonic integrated optical sensor based on a dual-polarization microring resonator with angular gratings on a silicon-on-insulator (SOI) waveguide, enabling simultaneous and precise refractive index (RI) and temperature measurements. Due to the distinct energy distributions for transverse electric ($\mathit{TE}$) and transverse magnetic ($\mathit{TM}$) modes in SOI waveguides, these modes show distinct sensitivity responses to the variation in ambient RI and temperature. Simultaneous measurements of both temperature and RI are enabled by exciting both these transverse modes in the microring resonator structure. Furthermore, incorporating angular gratings into the microring resonator’s inner sidewall extends the temperature measurement range by mitigating free spectral range limitations. This work presents a novel approach to dual-polarization microring resonators with angular gratings, offering an enhanced temperature measurement range and detection limit in optical sensing applications requiring an extended temperature range. The proposed structure is able to yield a simulated temperature measurement range of approximately 35 nm with a detection limit as low as $2.99\times {10}^{-5}$. The achieved temperature sensitivity is 334 pm/°C and RI sensitivity is 13.33 nm/RIU for the ${\mathit{TE}}_0$ mode, while the ${\mathit{TM}}_0$ mode exhibits a temperature sensitivity of 260 pm/°C and an RI sensitivity of 76.66 nm/RIU. Full article

This paper presents the first demonstration and comparison of two identical oscillator circuits employing piezoelectric zinc oxide (ZnO) microelectromechanical systems (MEMS) resonators, implemented on conventional printed-circuit-board (PCB) and three-dimensional (3D)-printed acrylonitrile butadiene styrene (ABS) substrates. Both oscillators operate simultaneously at dual frequencies (260 MHz and 437 MHz) without the need for additional circuitry. The MEMS resonators, fabricated on silicon-on-insulator (SOI) wafers, exhibit high-quality factors (Q), ensuring superior phase noise performance. Experimental results indicate that the oscillator packaged using 3D-printed chip-carrier assembly achieves a 2–3 dB improvement in phase noise compared to the PCB-based oscillator, attributed to the ABS substrate’s lower dielectric loss and reduced parasitic effects at radio frequency (RF). Specifically, phase noise values between −84 and −77 dBc/Hz at 1 kHz offset and a noise floor of −163 dBc/Hz at far-from-carrier offset were achieved. Additionally, the 3D-printed ABS-based oscillator delivers notably higher output power (4.575 dBm at 260 MHz and 0.147 dBm at 437 MHz). To facilitate modular characterization, advanced packaging techniques leveraging precise 3D-printed encapsulation with sub-100 μm lateral interconnects were employed. These ensured robust packaging integrity without compromising oscillator performance. Furthermore, a comparison between two transistor technologies—a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) and an enhancement-mode pseudomorphic high-electron-mobility transistor (E-pHEMT)—demonstrated that SiGe HBT transistors provide superior phase noise characteristics at close-to-carrier offset frequencies, with a significant 11 dB improvement observed at 1 kHz offset. These results highlight the promising potential of 3D-printed chip-carrier packaging techniques in high-performance MEMS oscillator applications. Full article

In this work, we report the formation of multiple mode-locking states in an Erbium/Ytterbium co-doped fiber laser, such as domain-wall (DW) dark pulses, high-order dark harmonic pulses, dissipative soliton resonance (DSR) pulses, and dual-wavelength h-shaped pulses. By increasing the pump power and adjusting the quarter-wave retarder (QWR) plates, we experimentally achieve 310th-order harmonic dark pulses. DSR pulses emerge at a pump power of 1.01 W and remain stable up to 9.07 W, reaching a maximum pulse width of 676 ns and a pulse energy of 1.608 µJ, while Dual-wavelength h-shaped pulses have a threshold of 1.42 W and maintain stability up to 9.07 W. Using a monochromator, we confirm that these h-shaped pulses result from the superposition of a soliton-like pulse and a DSR-like pulse, emitting at different wavelengths but locked in time. The fundamental repetition rate for dark pulsing, DSR, and h-shaped pulses is 321.34 kHz. This study provides new insights into complex pulse dynamics in fiber lasers and demonstrates the versatile emission regimes achievable through precise pump and polarization control. Full article

In this paper, a printed hybrid-mode antenna for dual-band circular polarization (CP) is proposed. In the proposed antenna, one T-shaped element is fed by a coplanar waveguide and one L-shaped element is loaded to the ground plane. The relationship between the antenna’s geometric parameters and the circular polarization characteristic (axial ratio) is examined through electric current distribution and radiation field components. In addition, the antenna’s resonant modes are investigated through characteristic mode analysis (CMA). Through parametric studies, the range of two frequency ratios is explored, revealing that the antenna operates as a dual-band single-sense CP antenna, even in ranges where the two frequency ratios (the ratio of high frequency to low frequency) are smaller compared to antennas in other studies. The proposed antenna has a frequency ratio of less than 1.5 between the two frequencies and can be flexibly designed. The proposed antenna is designed for the 2.5 GHz band and 3.5 GHz band. The measured bandwidths of 10 dB impedance with a 3 dB axial ratio are 2.35–2.52 GHz and 3.36–3.71 GHz, respectively. Full article

In this paper, we implement a compact switchable bandpass filter on a 50 Ω microstrip line. The proposed structure consists of an input/output stage with one end terminated at 50 Ω, a C-shaped-open loop resonator, and two L-shaped-open loop resonators. The proposed filter operates in four different modes depending on the on/off combination of the five PIN diodes. Each mode includes a dual-band pass filter (DB-BPF) designed for the 1.4 GHz and 5.1 GHz bands, another DB-BPF covering the 2.4 GHz and 4.2 GHz bands, a wideband BPF with a bandwidth ranging from 2 to 4.5 GHz, and an all-pass filter (APF) that allows all frequencies to pass through. The proposed structure is extremely compact because it is implemented on a 50 Ω line without any additional space. Full article

Terahertz (THz) biosensing faces critical challenges in balancing high sensitivity and broadband spectral coverage, particularly under miniaturized device constraints. Conventional quasi-bound states in the continuum (QBIC) metasurfaces achieve high quality factor (Q) but suffer from narrow bandwidth, while angle-scanning strategies for broadband detection require complex large-angle illumination. Here, we propose a symmetry-engineered, all-dielectric metasurface that leverages multipolar interference coupling to overcome this limitation. By introducing angular perturbation, the metasurface transforms the original magnetic dipole (MD)-dominated QBIC resonance into hybridized, multipolar modes. It arises from the interference coupling between MD, toroidal dipole (TD), and magnetic quadrupole (MQ). This mechanism induces dual counter-directional, frequency-shifted, resonance branches within angular variations below 16°, achieving simultaneous 0.42 THz broadband coverage and high Q of 499. Furthermore, a derived analytical model based on Maxwell equations and mode coupling theory rigorously validates the linear relationship between frequency splitting interval and incident angle with the Relative Root Mean Square Error (RRMSE) of 1.4% and the coefficient of determination ($R^2$) of 0.99. This work establishes a paradigm for miniaturized THz biosensors, advancing applications in practical molecular diagnostics and multi-analyte screening. Full article

This study proposes the development of a dual-wavelength optical fiber sensor (DWOFS) that integrates two optical fiber structures in a multimode transmission line to measure the refractive index and temperature of a liquid concurrently. One structure is based on a refractive index sensor that utilizes surface plasmon resonance, comprising a 5 mm long single-mode fiber (SMF) section coated with chromium/gold (Cr/Au) films. The secondary structure employs a multimode interferometer with a 29 mm long no-core fiber (NCF) section covered with a thick layer of polydimethylsiloxane (PDMS) to measure temperature. The measurements obtained reveal two distinct drops in the transmission spectrum at approximately 600 nm and 1550 nm, respectively, enabling precise measurement of the two parameters. The sensor demonstrates a high degree of sensitivity to both refractive index and temperature, spanning the visible ($2770.30\mathrm{n}\mathrm{m}/\mathrm{R}\mathrm{I}\mathrm{U}$) and infrared $(-0.178\mathrm{n}\mathrm{m}/°\mathrm{C}$) regions of the spectra, respectively. Furthermore, the thermo-optical coefficient for water $({-0.9928\times 10}^{-4}\mathrm{R}\mathrm{I}\mathrm{U}/°\mathrm{C})$ was estimated. The proposed sensor offers a compact solution for the simultaneous measurement of refractive index and temperature in liquid samples for a variety of applications, including biological, environmental, and healthcare research. Full article

To address the inherent contradiction between low-profile design and high gain in traditional omnidirectional antennas, as well as the narrow bandwidth constraints of ENZ antennas, this study presents a dual-mode ENZ-FP collaborative resonant antenna array design utilizing a substrate-integrated waveguide (SIW). Through systematic analysis of ENZ media’s quasi-static field distribution, we innovatively integrated it with Fabry–Perot (F–P) resonance, achieving unprecedented dual-band omnidirectional radiation at 5.18 GHz and 5.72 GHz within a single ENZ antenna configuration for the first time. The directivity of both frequencies reached 12.0 dBi, with a remarkably low profile of only 0.018λ. We then extended this design to an ENZ-FP dual-mode beam-scanning array. By incorporating phase control technology, we achieved wide-angle scanning despite low-profile constraints. The measured 3 dB beam coverage angles at the dual frequencies were ±63° and ±65°, respectively. Moreover, by loading the impedance matching network, the −10 dB impedance bandwidth of the antenna array was further extended to 2.4% and 2.7%, respectively, thus overcoming the narrowband limitations of the ENZ antenna and enhancing practical applicability. The antennas were manufactured using PCB (Printed Circuit Board) technology, offering high integration and cost efficiency. This provides a new paradigm for UAV (Unmanned Aerial Vehicle) communication and radar detection systems featuring multi-band operation, a low-profile design, and flexible beam control capabilities. Full article

A circularly polarized (CP) textile antenna is investigated for concurrent on- and off-body wireless communications in the 2.38 GHz medical body area network and 5.8 GHz industrial, scientific, and medical bands in the wireless body area network. The proposed scheme consists of a square microstrip patch antenna (MPA), in which four shorting pins are employed to tune the two resonate modes of TM₁₀ and TM₀₀. Notably, the slant corners on MPA are cut symmetrically to realize unidirectional CP radiation, enabling off-body communication. Moreover, four rotating L-shaped parasite elements are loaded to excite the horizontal polarization mode (TM_hp), which is combined with the TM₀₀ mode to implement CP omnidirectional radiation along the human body. For verification, a proof-of-concept prototype with the dimensions of 45 mm × 45 mm × 2 mm was fabricated and characterized. The measured −10 dB impedance bandwidths of 2.5% and 6.7%, the 3 dB AR bandwidths of 2.5% and 2.7%, and the maximum realized gains of −2.8 and 6.8 dBic are achieved in dual bands, respectively. The experimental tests, such as human body loading, structural deformation, and humidity variation, were carried out. In addition, the wireless communication capability was measured and the radiation safety is evaluated. These performances show that the proposed antenna is an appropriate choice for multifunctional wearable applications. Full article

Dual-mode sensors are currently facing difficulties in achieving independent sensing of parameters as well as low sensitivity. In this paper, we propose a dual-mode sensor using the finite element method (FEM) based on a coupled silver–PDMS–gold (SPG) cavity. We coupled a square ring resonant cavity with a double-ring resonant cavity structure, thus identifying a unique resonant cavity structure. The square ring resonator is made of silver and a double-ring resonant cavity filled with PDMS. Our proposed SPG cavity can independently achieve temperature and refractive index sensing. The SPG cavity enables us to obtain the highest biosensing sensitivity of about 1030 nm/RIU and the highest temperature sensitivity of about 216 pm/K. In addition, SPG cavities have excellent tolerances for geometric parameters. Our results provide new methodologies for metasurface design for dual-mode sensing. Full article

This study presents a novel method for dynamically tuning singular states in one-dimensional (1D) photonic lattices (PLs) using air-slit-based structural modifications. Singular states, arising from symmetry-breaking-induced resonance radiation, generate diverse spectral features through interactions between resonance modes and background radiation. By strategically incorporating air slits to break symmetry in 1D PLs, we demonstrated effective control of resonance positions, enabling dual functionalities including narrowband band pass and notch filtering. These singular states originate from asymmetric guided-mode resonances (aGMRs), which can be interpreted by analytical modeling of the equivalent slab waveguide. Moreover, the introduction of multiple air slits significantly enhances spectral tunability by inducing multiple folding behaviors in the resonance bands. This approach allows for effective manipulation of optical properties through simple adjustments of air-slit displacements. This work provides great potential for designing multifunctional photonic devices with advanced metamaterial technologies. Full article

The detrimental effects of low-frequency vibrations on the measurement accuracy of commercial high-precision instrumentation demand urgent resolution, particularly for instruments requiring <1 μm positioning stability. Conventional base-mounted active damping systems exhibit limitations in suppressing the structural resonance induced by passive isolators—especially when the environmental vibration intensity surpasses the standard thresholds. Therefore, in this study, we developed an innovative multi-mode control architecture to substantially enhance the vibration-damping capabilities of the DCSMS. The proposed methodology synergistically integrates foundation vibration isolators with embedded passive modules through a dual-stage spring-mass system optimization framework. Experimental validation combining ADAMS–MATLAB multi-physics co-simulation, complemented by a decoupling analytical control model based on the vibrational transmission characteristics of the source propagation path, substantiated the efficacy of the proposed control methodology. Full article

This paper focuses on the development and experimental validation of a single-phase modular multilevel converter (MMC) based on a battery energy storage system (BESS) for residential uninterruptible power supply (UPS) with two-level active SoC balancing control. The configuration and mathematical modeling of the single-phase MMC-BESS are first presented, followed by the details of the control strategies, including dual-loop output voltage and current control in islanded mode, grid-connected control, circulating current control, and two-level active state-of-charge (SoC) balancing control. The design and optimization of the quasi-proportional-resonant (QPR) controllers were investigated by using particle swarm optimization (PSO). Simulation models were built to explore the operating characteristics of the UPS under islanded mode with an RL load and grid-connected mode and assess the control performance. A 500 W experimental prototype was developed and is herein presented, including results under different operating conditions of the MMC-BESS. The experimental results show that for both RL load and grid-connected tests, balancing was achieved. The response time to track the reference value was two grid periods (0.04 s). In the islanded mode test, the THD was 1.37% and 4.59% for the voltage and current, respectively, while in the grid-connected mode test, these values were 1.72% and 4.24% for voltage and current, respectively. Full article

MEMS stiffness-tunable devices, owing to their low resonant frequency and high sensitivity, have been widely adopted in fields such as biological force sensing, vibration sensing, and inertial sensing. However, traditional stress-effect-based stiffness-adjustment methods offer limited tuning range. This paper introduces a novel stiffness-tuning mechanism based on the principle of stiffness compensation, integrating positive stiffness springs with V-shaped negative stiffness springs in a parallel configuration. A self-locking mechanism enables precise control of the mechanical preloading on the negative stiffness structures to realize stiffness adjustment. This design is prototyped by microscale fabrication techniques and is suitable for miniaturization. The experimental results confirm a stiffness reduction of over 90% and demonstrate bistability. These findings highlight the potential of the design for high-sensitivity MEMS accelerometers and dual-mode optical switches with low switching voltage. Full article

Controlling the surface plasmon resonances of metal nanostructures is crucial for advancing numerous high-sensitivity optical (bio)sensing applications. Furthermore, dynamically adjusting these resonances enables real-time tuning of the spectrum of enhanced electromagnetic fields in the near field, thereby regulating the optical interactions between molecules and the metal surface. In this study, we investigate the plasmonic behavior of linear oligomers composed of gold nanospheres using finite-difference time-domain electromagnetic simulations. The extinction spectra of linear arrangements such as dimers, trimers, and quadrumers are obtained for different sphere sizes, interparticle gaps, and polarization of the incident light. In view of (bio)sensing applications based on plasmon-enhanced optical spectroscopy such as surface-enhanced Raman/fluorescence (SERS/SEF), the sensitivity of various coupled plasmon modes to the variation of the interparticle gap is evaluated. The achievement of both red-shifting and blue-shifting plasmon modes offers ways to mechanically control the optical response of the linear oligomers in real-time and design new optical sensing protocols. Based on these findings, both an approach for trapping molecules into SERS hotspots and an approach for dual-mode SERS/SEF using a single excitation wavelength are proposed, contributing to the future development of (bio)sensing protocols. Full article