Search Results (97)

This article presents a comprehensive modeling and simulation framework for a capacitive MEMS accelerometer integrated with a sigma-delta analog-to-digital converter (ADC), with a focus on applications in wearable health and motion monitoring devices. The accelerometer used in the system is connected to a smartphone equipped with dedicated software and will be used to assess the risk of falling, which is crucial for patients with balance disorders. The authors designed the accelerometer with special attention paid to the specification required in a system, where the acceleration is ±2 g and the frequency is 100 Hz. They investigated the sensor’s behavior in the DC, AC, and time domains, capturing both the mechanical response of the proof mass and the resulting changes in output capacitance due to external acceleration. A key component of the simulation is the implementation of a second-order sigma-delta modulator designed to digitize the small capacitance variations generated by the sensor. The Simulink model includes the complete signal path from analog input to quantization, filtering, decimation, and digital-to-analog reconstruction. By combining MEMS+ modeling with MATLAB-based system-level simulations, the workflow offers a fast and flexible alternative to traditional finite element methods and facilitates early-stage design optimization for MEMS sensor systems intended for real-world deployment. Full article

Terahertz (THz) frequencies, spanning from 0.1 to 1 THz, are poised to play a pivotal role in the development of future 6G wireless communication systems. These systems aim to utilize photonic technologies to enable ultra-high data rates—on the order of terabits per second—while maintaining low latency and high efficiency. In this work, we present a novel photonic method for generating sub-THz vector signals within the THz band, employing a semiconductor optical amplifier (SOA) and phase modulator (PM) to create an optical frequency comb, combined with in-phase and quadrature (IQ) modulation techniques. We demonstrate, both through simulation and experimental setup, the generation and successful transmission of a 0.1 THz vector. The process involves driving the PM with a 12.5 GHz radio frequency signal to produce the optical comb; then, heterodyne beating in a uni-traveling carrier photodiode (UTC-PD) generates the 0.1 THz radio frequency signal. This signal is transmitted over distances of up to 30 km using single-mode fiber. The resulting 0.1 THz electrical vector signal, modulated with quadrature phase shift keying (QPSK), achieves a bit error ratio (BER) below the hard-decision forward error correction (HD-FEC) threshold of ${3.8 \times 10}^{-3}$. To the best of our knowledge, this is the first experimental demonstration of a 0.1 THz photonic vector THz wave based on an SOA and a simple PM-driven optical frequency comb. Full article

By leveraging the high sensitivity of acousto-optic modulators to microwave signals, their integration into RFID systems can significantly improve the detection of faint microwave signals. Traditional acousto-optic modulators, which use bidirectional uniform comb transducers (IDTs), suffer from a 50% microwave signal loss due to the diffraction efficiency being less than 50%, complicating the accurate identification of already weak signals. This paper presents a solution to the 50% loss issue by replacing the IDT with a floating electrode unidirectional transducer (FEUDT), a key structure in detecting microwave signals. The resulting samples exhibited an optical waveguide insertion loss of 8.73 dB, a mode field diameter of 6.48 $\mathsf{\mu }$m, an operating frequency of 141.2 MHz, and a diffraction efficiency of 61.72%, and required only 0.57 W of driving power. Comparative empirical tests with traditional transducers under identical conditions demonstrated that the FEUDT-based acousto-optic modulator surpassed the 50% diffraction efficiency limit of conventional modulators, which facilitated the detection of weak microwave signals. Full article

We observed tunable characteristics of optical frequency combs (OFCs) generated from InGaAs/GaAs double quantum wells (DQWs) asymmetric waveguide two-section mode-locked lasers (TS-MLLs). This involves an asymmetric waveguide mode-locked semiconductor laser (AWML-SL) operating at a center wavelength of net modal gain of approximately 1.06 µm, which indicates a stable pulse shape, with the power-current(P-I) characteristic curve revealing a small difference between forward and reverse drive currents in the gain region. Under different operating conditions, the laser exhibits the characteristics of OFCs. And the pulse interval in the timing and the peak interval in the frequency domain show a periodic alternating change trend with the increase in the gain current. This tunable characteristic is reported for the first time. The study demonstrates the feasibility of generating tunable optical combs using a monolithic integrated two-section mode-locked semiconductor laser (MI-TS-MLL). This has important reference value for the application of OFCs generated from MI-TS-MLLs or integrated optical chips. Full article

We propose and demonstrate a microwave photonic system to generate multiband and multi-format microwave waveforms based on an actively mode-locked optoelectronic oscillator (AML-OEO) using a dual-polarization dual-drive Mach–Zehnder modulator (DPol-DDMZM). In the proposed system, the upper DDMZM is injected by two baseband single-chirped signals, and the lower DDMZM is biased to realize single-sideband (SSB) modulation using a 90° hybrid coupler. The lower DDMZM is also used to construct an AML-OEO loop, which outputs microwave frequency comb signals. By setting the phase difference in the applied two single-chirped signals, multiband up-, down-, and dual-chirped microwave signals are successfully generated. Furthermore, the tunability of the system can be realized by adjusting the frequency and power of the injection signal in the AML-OEO loop, the passband of the electrical filter, and the chirp rate of the single-chirped signal. The proposed scheme is theoretically analyzed and experimentally verified. Full article

Molecular spectroscopy, with a legacy spanning over a century, has profoundly enriched our understanding of the microscopic world, driving major advancements across science and engineering. Over time, this field has steadily advanced, incorporating innovations such as lasers and digital computers to reach new levels of precision and sensitivity. Over the past decade, the integration of high-speed embedded electronic systems and advanced light sources has ushered molecular spectroscopy into a new era, characterized by extensive parallelism and enhanced sensitivity. This review delves into two pioneering technologies that embody recent advancements in molecular spectroscopy: Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectroscopy and optical frequency comb (OFC) spectroscopy. We provide an overview of the fundamental principles behind these methods, examine their most impactful applications across diverse fields, and discuss their potential to drive future developments in molecular spectroscopy. By highlighting these technologies, we aim to underscore the transformative impact of integrating high-speed digital electronics and advanced light sources with molecular spectroscopy, enabling extensive parallelism and paving the way for groundbreaking discoveries and innovations in this rapidly evolving field. Full article

The MEMS scanning micromirror requires angle sensors to provide real-time angle feedback during operation, ensuring a stable and accurate deflection of the micromirror. This paper proposes a method for integrating piezoresistive sensors on the torsion axis of electrostatic MEMS micromirrors to detect the deflection angle. The design uses a multi-layer bonding process to realize a vertical comb-driven structure. The device structure is designed as a double-layer structure, in which the top layer is the ground layer and integrates with piezoresistive sensor. This approach avoids crosstalk between the applied drive voltage and the piezoresistive sensor. This design also optimizes the sensor’s size, improving sensitivity. A MEMS two-dimensional (2D) scanning micromirror with a 1 mm mirror diameter was designed and fabricated. The test results indicated that, in a vacuum environment, the torsional resonance frequencies of the micromirror’s fast axis and slow axis were 17.68 kHz and 2.225 kHz, respectively. When driving voltages of 33 V and 40 V were applied to the fast axis and slow axis of the micromirror, the corresponding optical scanning angles were 55° and 45°, respectively. The piezoresistive sensor effectively detects the micromirror’s deflection state, and optimizing the sensor’s size achieved a sensitivity of 13.87 mV/V/°. The output voltage of the piezoresistive sensor shows a good linear relationship with the micromirror’s deflection angle, enabling closed-loop feedback control of the electrostatic MEMS micromirror. Full article

Background/Objectives: Populations in Mediterranean countries are abandoning the traditional Mediterranean diet (MD) and lifestyle, shifting towards unhealthier habits due to profound cultural and socioeconomic changes. The SWITCHtoHEALTHY project aims to demonstrate the effectiveness of a multi-component nutritional intervention to improve the adherence of families to the MD in three Mediterranean countries, thus prompting a dietary behavior change. Methods: A parallel, randomized, single-blinded, and controlled multicentric nutritional intervention study will be conducted over 3 months in 480 families with children and adolescents aged 3–17 years from Spain, Morocco, and Turkey. The multi-component intervention will combine digital interactive tools, hands-on educational materials, and easy-to-eat healthy snacks developed for this study. Through the developed SWITCHtoHEALTHY app, families will receive personalized weekly meal plans, which also consider what children eat at school. The engagement of all family members will be prompted by using a life simulation game. In addition, a set of activities and educational materials for adolescents based on a learning-through-playing approach will be codesigned. Innovative and sustainable plant-based snacks will be developed and introduced into the children’s dietary plan as healthy alternatives for between meals. By using a full-factorial design, families will be randomized into eight groups (one control and seven interventions) to test the independent and combined effects of each component (application and/or educational materials and/or snacks). The impact of the intervention on diet quality, economy, and the environment, as well as on classical anthropometric parameters and vital signs, will be assessed in three different visits. The COM-B behavioral model will be used to assess essential factors driving the behavior change. The main outcome will be adherence to the MD assessed through MEDAS in adults and KIDMED in children and adolescents. Conclusions: SWITCHtoHEALTHY will provide new insights into the use of sustained models for inducing dietary and lifestyle behavior changes in the family setting. It will facilitate generating, boosting, and maintaining the switch to a healthier MD dietary pattern across the Mediterranean area. Registered Trial, National Institutes of Health, ClinicalTrials.gov (NCT06057324). Full article

Combing through Chinese energy-related policy texts and exploring the development path of energy restructuring are significant steps towards a better understanding of the history of energy restructuring in the process of building a moderately prosperous society in all aspects. To explore the various paths driving the transformation of China’s energy structure, the energy policies promulgated at the national level from 2001 to 2020 in China were systematically compiled. Based on the policy tool perspective, a theoretical framework for influencing China’s energy structure transition was proposed in three dimensions: objectives, tools, and intensity. A total of 39 national energy policy texts were analyzed using a fuzzy set qualitative comparative analysis method. The results show that (1) the consistency levels of individual preconditions were all below 0.9, which does not constitute a necessary condition for the transformation of China’s energy structure; (2) the sufficiency analysis identified three paths of China’s energy structure transformation, which can be described as models driven by “multiple objectives + information”, “single objective + information”, and “single objective”; (3) energy restructuring is a goal-oriented process; the clarity and certainty of the efficient and green objectives of energy policies have a facilitating effect on energy restructuring, and the support of information technology provides an important guarantee for energy restructuring; (4) compared with European and American countries, it was found that China’s energy policy tools were characterized by an emphasis on macro-planning, insufficient connectivity, and marked tendencies in practice. Full article

We present the generation of attosecond gamma rays via inverse Compton scattering within the framework of laser wakefield acceleration through 2D Particle-In-Cell simulations. Utilizing the near-threshold ionization injection mechanism, an attosecond micro-bunched electron beam characterized by a comb-like current density profile can be achieved with a linearly polarized laser at an intensity of a₀ = 1.5. The micro-bunched beam provides a beam energy of approximately 300 MeV and achieves a minimum relative energy spread of about 1.64% after undergoing 2 mm of acceleration. In the inverse Compton scattering scheme, these attosecond electron micro-bunches interact with the reflected driving laser pulse, resulting in the attosecond gamma-ray radiation exhibiting similar structures. Individual spatial-separated gamma-ray pulses exhibit a length of approximately 260–300 as, with a critical energy of 2.0 ± 0.2 MeV. The separated attosecond gamma-ray source owns a peak brilliance of ~10²² photons s⁻¹ mm⁻² mrad⁻² 0.1% BW. This brilliance is competitive in a laboratory for multi-MeV γ-ray sources with a laser intensity of I = 5 $\times$ 10¹⁸ W/cm². Such attosecond gamma-ray radiation offers promising applications requiring ultrashort X-ray/gamma ray sources. Full article

This study presents a comprehensive numerical investigation on the generation of a microwave frequency comb (MFC) using a semiconductor laser subjected to periodic-modulated optical injection. To enhance performance, optoelectronic feedback is incorporated through a dual-drive Mach–Zehnder modulator. The results show that the first optoelectronic feedback loop, with a delay time inversely proportional to the modulation frequency, can optimize MFC generation through a mode-locking effect and the second optoelectronic feedback loop with a multiple delay time of the first one can further enhance the performance of the MFC. The comb linewidth appears to decrease with the increase in the second-loop delay time in the power function. These results are consistent with experimental observations reported in the literature. We also explore the impact of the feedback index on comb contrast, the statistical characteristics of the central 128 lines within the MFC, and side peak suppression. The simulation results demonstrate the presence of an optimal feedback index. The study also reveals that linewidth reduction, through increasing the feedback index and delay time, comes at the cost of declining side peak suppression. These findings collectively contribute to a deeper understanding of the factors influencing MFC generation and pave the way for the design and optimization of high-performance MFC systems for various applications. Full article

We are developing a phase-modulating micro mirror-array spatial light modulator to be used for real holography within the EU-funded project REALHOLO, featuring millions of pixels that can be individually positioned in a piston mode at a large frame rate. We found earlier that an electrostatic comb-drive array offers the best performance for the actuators: sufficient yoke forces for fast switching even at low voltages compatible with the CMOS addressing backplane. In our first design, the well-known electrostatic cross-talk issue had already been much smaller than would have been possible for parallel-plate actuators, but it was still larger than the precision requirements for high-image-quality holography. In this paper, we report on our analysis of the crucial regions for the electrostatic cross-talk and ways to reduce it while observing manufacturing constraints as well as avoiding excessively high field strengths that might lead to electrical breakdown. Finally, we present a solution that, in FEM simulations, reduces the remaining cross-talk to well below the required specification limit. This solution can be manufactured without any additional processing steps and suffers only a very small reduction of the yoke forces. Full article

The paper presents the noise analysis of a MEMS and ASIC readout integrated circuit (ROIC) constituting the accelerometer developed in the frame of the InnoReh project, aiming at the development of methods for monitoring patients with imbalance disorders. Several experiments were performed at different temperatures and in different configurations: ROIC alone, ROIC with emulated parasitic capacitances, MEMS and ROIC in separate packages, and MEMS and ROIC in a single package. Many noise/interference sources were considered. The results obtained experimentally were compared to the results of theoretical investigations and were within the same order of magnitude, although in practice, the observed noise was always greater than the theoretical estimation. The paper also includes an in-depth analysis to explain these differences. Moreover, it is argued that, in terms of noise, the MEMS sensing element, and not the ROIC, is the quality-limiting factor. Full article

Guiding mechanisms are among the most elementary components of in-plane micro-electro-mechanical systems (MEMS). Usually, a spring is desired that is compliant in only one direction and stiff in other directions. We introduce triangular springs with a preset tilting angle. The tilting angle lowers the force reaction in the displacement direction and implements a constant-force reaction whereby the maximum selectivity of the tilted triangular spring is shifted to larger displacements. Thus, the tilted triangular springs can increase the lateral stability of comb-drive actuators. We show tilted triangular springs exhibiting constant forces in a deflection range of about 75 µm to 175 µm. Full article

In this paper, we present a novel three-dimensional (3D) coupled configuration of piezoelectric micromachined ultrasound transducers (pMUTs) by combing a curved and an annular diaphragm for transmit performance optimization in biomedical applications. An analytical equivalent circuit model (EQC) is developed with varied excitation methods to incorporate the acoustic–structure coupling of the curved and annular diaphragm-coupled pMUTs (CAC-pMUTs). The model-derived results align well with the reference simulated by the finite element method (FEM). Using this EQC model, we optimize the key design parameters of the CAC-pMUTs in order to improve the output sound pressure, including the width of the annular membrane, the thickness of the passive layer, and the phase difference of the driving voltage. In the anti-phase mode, the designed CAC-pMUTs demonstrate a transmit efficiency 285 times higher than that of single annular pMUTs. This substantial improvement underscores the potential of CAC-pMUTs for large array applications. Full article