Hundreds Of kHz Research Articles

Four ribbons of double-layer graphene suspending masses for NEMS applications

Graphene ribbons with a suspended proof mass for nanomechanical systems have been rarely studied. Here, we report three types of nanomechanical devices consisting of graphene ribbons (two ribbons, four ribbons-cross and four ribbons-parallel) with suspended Si proof masses and studied their mechanical properties. The resonance frequencies and built-in stresses of three types of devices ranged from tens of kHz to hundreds of kHz, and from 82.61 MPa to 545.73 MPa, respectively, both of which decrease with the increase of the size of proof mass. The devices with four graphene ribbons featured higher resonance frequencies and spring constants, but lower built-in stresses than two ribbon devices under otherwise identical conditions. The Young’s modulus and fracture strain of double-layer graphene were measured to be 0.34 TPa and 1.13% respectively, by using the experimental data and finite element analysis (FEA) simulations. Our studies would lay the foundation for understanding of mechanical properties of graphene ribbons with a suspended proof mass and their potential applications in nanoelectromechanical systems.

Multi-Wavelength Narrow-Spacing Laser Frequency Stabilization Technology Based on Fabry-Perot Etalon

Classical frequency-stabilized lasers have achieved high-frequency stability and reproducibility; however, their extensive wavelength spacing limits their utility in various scenarios. This study introduces a novel frequency-stabilized laser scheme that integrates a Fabry-Perot etalon (FPE) with digital control technology and wavelength modulation techniques. The FPE, characterized by multiple transmission peaks at minimal frequency intervals, provides stable frequency references for different lasers, thereby enhancing the system’s flexibility and adaptability. An error signal is derived from the first-order differentiation of the FPE’s transmission curve. A 180° phase difference was observed in the feedback output signal when the laser’s central frequency diverged from the reference, determining that the direction of the frequency control was accordingly determined.Employing feedback control, the laser’s output frequency is stabilized at the transmission peak frequency of the FPE. Experimental results demonstrate that this stabilization scheme effectively locks the laser’s output wavelength to different transmission peak frequencies of the FPE, achieving 25 GHz wavelength spacing. The frequency stability is improved by two orders of magnitude on a second-level timescale, maintained within hundreds of kHz, equating to a frequency stability level of 10−10.

A Step‐by‐Step Approach for Replacing Si‐IGBTs With SiC‐MOSFETs Modules in Industrial Power Converters

ABSTRACTThis work presents a step‐by‐step approach for replacing Si‐IGBTs with SiC‐MOSFETs modules in a 9‐kW commercial double‐conversion UPS. Incremental modifications are applied to the original system, considering variations in switching frequency and evaluating its influence on losses and total volume. Through the use of Si‐IGBT transistors and redesigning the system, the volume and losses are analyzed for switching frequencies between 10 and 17 kHz. The IGBT showed limitations around 17 kHz, with high losses due to tail current. With SiC‐MOSFETs, the switching frequency is increased, resulting in smaller filter volumes. The SiC module allowed operation at frequencies in the tens and hundreds of kHz, with relatively low switching losses, which significantly reduced the volume of filters and heat transfer systems. These technological advancements resulted in reductions of up to 78% in the total volume and improved efficiency, enabling operation at lower temperatures and potentially increasing the lifetime of components.

Cpa-free Yb:YAG thin-disk regenerative amplifier laser with hundreds of watts, hundreds of kHz, and hundreds of picoseconds

This paper introduces a CPA-free Yb:YAG thin-disk regenerative amplifier laser system. The seed pulse is generated by a passive mode-locked picosecond oscillator based on a semiconductor saturable absorber mirror, with a center wavelength of 1030.7 nm, a pulse width of 7.7 ps, and a repetition frequency of 26.3 MHz. After stretched and pre-amplified by an all-fiber front stage, the seed with a pulse width of 201.3 ps and a pulse energy of 15.2 nJ was obtained, then injected into the thin-disk regenerative amplifier. Yb:YAG crystal was chosen as the material for the thin-disk, with 100 μm thickness, 9 mm diameter and 7 at.% doping rate. In order to increase the one-way round-trip gain of the thin-disk regenerative amplifier, a symmetrical dual-pass resonant cavity was designed to double the number of passing through the crystal on a round trip in the regenerative resonant cavity to reduce the times of cycles, intra-cavity loss and improve optical efficiency. We used a 969 nm fiber-coupled semiconductor laser as the pump source to pump the Yb:YAG thin-disk crystal. With zero-phonon line pumping technology, the quantum loss and thermal effect were reduced. In the end, we obtained a regenerative amplification output with an average power of 104.5 W, a repetition frequency of 200 kHz, a pulse width of 143.9 ps, and a spectrum width of 0.39 nm. The amplified pulse had quite good beam quality with Mx2 = 1.09 and My2 = 1.14.

A laser ultrasound system to non-invasively measure compression waves in granular ice mixes

Accurate knowledge of snow mechanical properties, including Young's modulus, shear modulus, Poisson's ratio, and density, is critical to many areas of snow science and to snow-related engineering problems. To facilitate the assessment of these properties, an innovative non-contacting laser ultrasound system (LUS) has been developed. This system acquires ultrasound waveform data at frequencies ranging from tens to hundreds of kHz in a controlled cold-lab environment. Two different LUS devices were compared in this study to determine which recorded more robust ultrasound in granular ice mix samples. We validated the ultrasound observations with poro-elastic traveltime modeling based on physical and empirical constitutive relationships, comparison to and replication of previous studies, and the use of other accredited snow property measurement systems, i.e., the SnowMicroPen. For ice mixes, we determined that the PSV-400 Scanning Vibrometer (Polytec GmbH) produces higher quality ultrasonic wavefield observations (i.e. has a better signal-to-noise ratio) than the VibroFlex Fiber Vibrometer (Polytec GmbH) in the lab conditions tested here. Using the PSV-400, we then demonstrated the utility of this new LUS to study the relationship between snow compression-wave speed and density during snow compaction experiments.

Real-Time Frequency Adaptive Tracking Control of the WPT System Based on Apparent Power Detection

In wireless power transfer (WPT) systems, inverters are used to achieve high-frequency conversion of DC/AC, and their conversion efficiency and working frequency are key factors affecting the system’s power transfer efficiency. In practical applications, many hardware issues, such as power transistor shutdown and loss, are the main reasons that affect the inverter conversion efficiency. On the other hand, the working frequency of WPT systems ranges from hundreds of kHz to a few MHz, and traditional voltage and current phasor estimation requires a very high sampling rate which is difficult to achieve. To overcome these limitations, this paper introduces a phase-shifting full bridge inverter using a zero-voltage switching (ZVS) soft switching technology to optimize the conversion efficiency of the inverter. Meanwhile, apparent power is introduced to detect the operating frequency and phase angle. Combined with an FPGA soft switching control strategy, this approach allows for the quick adjustment of the driving pulse of MOS transistors, as well as the voltage and current at the transmitting end, to a completely symmetrical state in real-time, effectively suppressing frequency offset and achieving efficient frequency tracking control and maximum efficiency tracking (MET) control of the WPT system. Through simulation and experiments, the ZVS soft switching technology has been achieved with the inverter control strategy, leading to improved conversion efficiency. The frequency offset that can be corrected can reach 0.1 Hz using the apparent power detection method, and the maximum transfer efficiency of the WPT system can reach 91%.

Ultrasonically induced nanofatigue monitoring during nanoindentation

The ultrasonic nanoindentation tip integrated into a nanoindenter operates at hundreds of kHz, inducing millions of load cycles within seconds at the localized mechanical contact point. Then operating on brittle submicron thick films such as SiC, the resulting accumulated nanofatigue exhibits different contact fracture modes. During the process of quasi-static loading with ultrasonic excitation, the ultrasonic nanoindentation tip monitors associated acoustic waveforms, which can provide additional insights into the nanofatigue process dynamics via advanced acoustic waveform analysis and deep learning classifications.

Integrating 2D Materials and Plasmonics on Lithium Niobate Platforms for Pulsed Laser Operation at the Nanoscale

AbstractThe current need for coherent light sources for integrated (nano)photonics motivates the search for novel laser designs emitting at technologically relevant wavelengths with high‐frequency stability and low power consumption. Here, a new monolithic architecture that integrates monolayer MoS2 and chains of silver nanoparticles on a rare‐earth (Nd3+) doped LiNbO3 platform is developed to demonstrate Q‐switched lasing operation at the nanoscale. The localized surface plasmons provided by the nanoparticle chains spatially confine the gain generated by Nd3+ ions at subwavelength scales, and large‐area monolayer MoS2 acts as saturable absorber. As a result, an ultra‐compact coherent pulsed light source delivering stable train pulses with repetition rates of hundreds of kHz and pulse duration of 1 µs is demonstrated without the need of any voltage‐driven optical modulation. Moreover, the monolithic integration of the different elements is achieved without sophisticated processing, and it is compatible with LiNbO3‐based photonics. The results highlight the robustness of the approach, which can be extended to other 2D materials and solid‐state gain media. Potential applications in communications, quantum computing, or ultra‐sensitive sensing can benefit from the synergy of the materials involved in this approach, which provides a wealth of opportunities for light control at reduced scales.

Design and simulation of an accelerometer based on NV center spin–strain coupling

The nitrogen-vacancy (NV) center quantum systems have emerged as versatile tools in the field of precision measurement because of their high sensitivity in spin state detection and miniaturization potential as solid-state platforms. In this paper, an acceleration sensing scheme based on NV spin–strain coupling is proposed, which can effectively eliminate the influence of the stray noise field introduced by traditional mechanical schemes. Through the finite element simulation, it is found that the measurement bandwidth of this ensemble NV spin system ranges from 3 kHz to hundreds of kHz with structure optimization. The required power is at the sub-μW level, corresponding to a noise-limited sensitivity of 6.7×10−5g/Hz . Compared with other types of accelerometers, this micro-sized diamond sensor proposed here has low power consumption, exquisite sensitivity, and integration potential. This research opens a fresh perspective to realize an accelerometer with appealing comprehensive performance applied in biomechanics and inertial measurement fields.

Fabrication of Fe-Based Nanocrystalline Powder-Pressed Magnetic Core and Application to Planar Reactor for Hundreds of kHz or Beyond

In this study, to decrease coercivity and iron loss for the Fe-Si-B-Nb-Cu-C nanocrystalline powder-pressed magnetic core for hundreds kHz or beyond, a post annealing after pressing the Fe-Si-B-Nb-Cu-C amorphous powder was executed for nanocrytallization and release of the residual strain induced through the pressing the powder. In addition, novel fabrication procedure for obtaining the small coercivity powdered magnetic core was proposed. It was found that the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core exhibited a saturation magnetization of 0.91 T, coercvity of 123 A/m, relative permeability of 32.5 and iron losses of 105 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 100kHz, 50mT and 2194 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 1MHz, 50mT. From the iron loss break-down for the fabricated Fe-Si-B-Nb-Cu-C nanocrystalline powdered magnetic core, its hysteresis and eddy current losses were smaller than those of Fe-Si-B-C-Cr powder-pressed magnetic core. In addition, a planar reactor was fabricated using the powder-pressed magnetic core, which had a size of 47×44×16 mm, DC coil resistance of 7.3mΩ, inductance of 12.1 μH, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -factor of about 127 at 1MHz and inductance drop of 4.1% at a superimposed DC current of 30A.

Integrated heterodyne laser Doppler vibrometer based on stress-optic frequency shift in silicon nitride

We demonstrate a compact heterodyne Laser Doppler Vibrometer (LDV) based on the realization of optical frequency shift in the silicon nitride photonic integration platform (TriPleX). We theoretically study, and experimentally evaluate two different photonic integrated optical frequency shifters (OFSs), utilizing serrodyne and single-sideband (SSB) modulation. Both OFSs employ stress-optic modulators (SOMs) based on the non-resonant piezoelectrical actuation of lead zirconate titanate (PZT) thin-films, deposited on top of the silicon nitride waveguides with a wafer-scale process. To improve the modulation bandwidth of the SOMs we investigate a novel configuration of the electrodes used for the actuation, where both electrodes are placed on top of the PZT layer. Using this top-top electrode configuration we report frequency shift of 100 kHz and 2.5 MHz, and suppression ratio of the unwanted sidebands of 22.1 dB and 39 dB, using the serrodyne and the SSB OFS, respectively. The best performing SOM structure induces 0.25π peak-to-peak sinusoidal phase-shift with 156 mW power dissipation at 2.5 MHz. We use the SSB-OFS in our compact LDV system to demonstrate vibration measurements in the kHz regime. The system comprises a dual-polarization coherent detector built in the PolyBoard platform, utilizing hybrid integration of InP photodiodes (PDs). High quality LDV performance with measurement of vibration frequencies up to several hundreds of kHz and displacement resolution of 10 pm are supported with our system.

Response of G-NUMEN LaBr3(Ce) Detectors to High Counting Rates

The G-NUMEN array is the future gamma spectrometer of the NUMEN experiment (nuclear matrix element for neutrinoless double beta decay), to be installed around the object point of the MAGNEX magnetic spectrometer at the INFN-LNS laboratory. This project aims to explore double-charge exchange (DCE) reactions in order to obtain crucial information about neutrinoless double beta decay (0νββ). The primary objective of the G-NUMEN array is to detect the gamma rays emitted from the de-excitation of the excited states that are populated via DCE reactions with a good energy resolution and detection efficiency, amidst a background composed of the transitions from competing reaction channels with far higher cross sections. To achieve this, G-NUMEN signals will be processed in coincidence with those generated by the detection of reaction ejectiles by the MAGNEX focal plane detector (FPD). Under the expected experimental conditions, G-NUMEN detectors will operate at high counting rates, of the order of hundreds of kHz per detector, while maintaining excellent energy and timing resolutions. The complete array will consist of over 100 LaBr3(Ce) scintillators. Initial tests were conducted on the first detectors of the array, allowing for the determination of their performance at high rates.

Microcontroller-Based Trapezoidal Slope Compensation Technique for Peak Current Mode Control at MHz Frequencies

Slope compensation is necessary for the peak cur-rent mode control technique to ensure the stability of the power converter. Micro-controllers (μCs) existing in the market implement the slope compensation using built-in digital to analog converters (DACs). DACs exhibit finite transient times, which can be negligible when the μCs are used to control the power converters at switching frequencies in the order of a few hundreds of kHz. However, for high device switching frequency (HDSF) operation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq 1\, \rm{MHz}$</tex-math></inline-formula> ), the DAC transient time becomes significant and can make it difficult, if not impossible, to achieve the conventional ramp slope compensation. Hence, in this paper, a novel concept of ‘trapezoidal’ slope compensation is proposed by considering the transient time of the μC. A detailed analysis is performed to understand the effect of the transient period on the converter stability. The proposed technique is validated with an experimental prototype of 400 W at 1 MHz switching frequency and it is shown to ensure stability of the converter at all operating points within the specification.

A Unified Differential Mode Noise Estimation Method and Filter Size Comparison in Single-Phase Multileg and Multilevel Totem-Pole PFC Converters

Wide band-gap power devices have enabled single-phase totem-pole (TP) power factor correction (PFC) converter designs to be switched at several tens of kHz under hard-switching and hundreds of kHz under soft-switching. It is straight-forward to analyze and compare the volume of boost inductor for TP PFC converters having multi-leg and multi-level configurations operating under continuous-conduction-mode (CCM) and critical-conduction-mode (CrM) at various switching frequencies; however, the impact of topology and switching frequency selections remains unchallenged for generated differential mode (DM) noise. This paper proposes a unified and generalized DM noise estimation method for multi-leg, and multi-level TP PFC converters operated under both CCM and CrM operation modes. The method has been verified with simulation results obtained from various TP PFC topologies, as well as experimental results obtained from single-leg CCM and 4-Level CCM TP PFC converters. The empirically determined boxed sizes of DM filters have been compared among various TP PFC topologies, and the best switching frequency for each topology has been determined with the integration of boost inductor volume comparison.

Telecom single-photon emitters in GaN operating at room temperature: embedment into bullseye antennas

Abstract The ideal single-photon source displaying high brightness and purity, emission on-demand, mature integration, practical communication wavelength (i.e., in the telecom range), and operating at room temperature does not exist yet. In 2018, a new single-photon source was discovered in gallium nitride (GaN) showing high potential thanks to its telecom wavelength emission, record-high brightness, good purity, and operation at room temperature. Despite all these assets, its coupling to photonic structures has not been achieved so far. In this article, we make a first step in this direction. First, we analyze whether stacking faults are indeed a necessary condition for obtaining such emitters in GaN layers. Then, we discuss the challenges associated to a low spatial density and to a spectrally wide distribution of emitters, which necessitate their location to be determined beforehand and the photonic structure resonance to be tuned to their emission wavelength. The design and fabrication of bullseye antennas are thoroughly described. Finally, we fabricate such bullseyes around telecom emitters and demonstrate that the embedded emitters are able to sustain the necessary clean-room process and still operate as single-photon emitters after the fabrication steps, with room-temperature purities up to 99% combined with repetition rates in the order of hundreds of kHz. The findings in this work demonstrate that telecom single-photon emitters in GaN operating at room temperature are well adapted for single-photon applications where brightness and purity are the required figures of merit, but highlight the numerous difficulties that still need to be overcome before they can be exploited in actual quantum photonic applications.

Fast modulation of surface plasmons based on the photothermal effect of nonvolatile solid thin films.

Nonvolatile phase change materials owing to their robust stability and reversibility have shown significant potential in nanophotonic switches and memory devices. However, their performances deteriorate as the thickness decreases below 10 nm due to the local deformation induced by the phase change, which makes them less compatible with plasmonic nanogaps. Here, we address this issue by photothermally modulating the refractive index of germanium antimony telluride (GST) placed in plasmonic nanogaps, which tunes plasmon resonances in the visible region below the melting point of GST, making such optical switching highly reversible at a rate of up to hundreds of ∼kHz. They are also demonstrated to modulate the waveguiding efficiency of propagating surface plasmons, which is based on the photothermal modulation of plasmons with the assistance of GST. Such hybrid nanoplasmonic system with cost-effective fabrication and efficient operation method provides a promising route towards integrated nanophotonic chips.

High Temperature Measurement with Low Cost, VCSEL-Based, Interrogation System Using Femtosecond Bragg Gratings.

In this article, a cost-effective and fast interrogating system for wide temperature measurement with Fiber Bragg Gratings is presented. The system consists of a Vertical Cavity Surface Emitting Laser (VCSEL) with a High Contrast Grating (HCG)-based cavity that allows for the fast tuning of the output wavelength. The work focuses on methods of bypassing the limitations of the used VCSEL laser, especially its relatively narrow tuning range. Moreover, an error analysis is provided by means of the VCSEL temperature instability and its influence on the system performance. A simple proof of concept of the measurement system is shown, where two femtosecond Bragg gratings were used to measure temperature in the range of 25 to 800 °C. In addition, an exemplary simulation of a system with sapphire Bragg gratings is provided, where we propose multiplexation in the wavelength and reflectance domains. The presented concept can be further used to measure a wide range of temperatures with scanning frequencies up to hundreds of kHz.

Free spectral range magnetic tuning of an integrated microcavity

Tunable whispering-gallery-mode (WGM) microcavities are promising devices for reconfigurable photonic applications such as widely tunable integrated lasers and reconfigurable optical filters for optical communication and information processing. Scaling up these devices demands the ability to tune the optical resonances in an integrated manner over a full free spectral range (FSR). Here we propose a high-speed full FSR magnetic tuning scheme of an integrated silicon nitride (Si3N4) double-disk microcavity. By coating a magnetostrictive film on the spokes and the central pad of the Si3N4 cavity, magnetic tuning can be realized using a microcoil integrated on the same chip. An FSR tuning can be achieved by combining magnetostrictive strain with strong optomechanical interactions provided by the double-disk microcavity. We calculate the required magnetic flux density to tune an FSR (BFSR) as a function of several key geometric parameters, including the air gap, radius, width of the spokes and ring of the double-disk cavities, as well as the thickness of the magnetostrictive film. The proposed structure enables a full FSR tuning with a required magnetic flux density of milli-Tesla (mT) level. We also study the dynamic response of the integrated device with an alternating current (AC) magnetic field driving, and find that the tuning speed can reach hundreds of kHz in the air.

Mathematical Expressions Useful for Tunable Properties of Simple Square Wave Generators

This paper compares two electronically controllable solutions of triangular and square wave generators benefiting from a single IC package including all necessary active elements (modular cells fabricated in I3T 0.35 µm ON Semiconductor process operating with ±1.65 V supply voltage). Internal cells are used for construction of building blocks of the generator (integrator and Schmitt trigger/comparator). Proposed solutions have adjustable parameters dependent on the values of DC control voltages and currents. Attention is given to the mathematical expressions for the advantageous tunability of these generators. Theoretical mathematical functions comparing the standard linear formula with special expression for the frequency adjustment are evaluated and compared with experimentally obtained results. Mathematical functions prove that the proposed topologies improve efficiency of tunability and reduce overall complexity of both generators. Features of proposed solutions were verified experimentally. Both single-parameter tunable designs target on the operation in bands from tens to hundreds of kHz (from 13 kHz up to 251 kHz for the driving voltage between 0.05 V and 1.0 V for the first solution; from 12 kHz up to 847 kHz for the driving current between 5 µA and 140 µA for the second solution). A comparison with similar solutions indicates beneficial performance of the proposed solutions in tunability ratio vs. driving parameter ratio and also because simplicity of circuitry is low. The qualitative evaluation and comparison of parameters of both circuits is given and confirms theoretical expectations.

Influence of Heat Accumulation on Morphology Debris Deposition and Wetting of LIPSS on Steel upon High Repetition Rate Femtosecond Pulses Irradiation

The fabrication of laser-induced periodic surface structures (LIPSS) over extended areas at high processing speeds requires the use of high repetition rate femtosecond lasers. It is known that industrially relevant materials such as steel experience heat accumulation when irradiated at repetition rates above some hundreds of kHz, and significant debris redeposition can take place. However, there are few studies on how the laser repetition rate influences both the debris deposition and the final LIPSS morphology. In this work, we present a study of fs laser-induced fabrication of low spatial frequency LIPSS (LSFL), with pulse repetition rates ranging from 10 kHz to 2 MHz on commercially available steel. The morphology of the laser-structured areas as well as the redeposited debris was characterized by scanning electron microscopy (SEM) and µ-Raman spectroscopy. To identify repetition rate ranges where heat accumulation is present during the irradiations, we developed a simple heat accumulation model that solves the heat equation in 1 dimension implementing a Forward differencing in Time and Central differencing in Space (FTCS) scheme. Contact angle measurements with water demonstrated the influence of heat accumulation and debris on the functional wetting behavior. The findings are directly relevant for the processing of metals using high repetition rate femtosecond lasers, enabling the identification of optimum conditions in terms of desired morphology, functionality, and throughput.