Traveling-wave Field Research Articles

Experimental demonstration of a liquid piston Stirling engine with a wet regenerator

In this study, a liquid piston Stirling engine with a water-absorbing wick to keep the regenerator wet (LPSE(wet)) was designed and built. The feasibility of operating the LPSE (wet) at lower temperatures to increase power output compared with that of a liquid piston Stirling engine with a dry regenerator (LPSE (dry)) was experimentally verified. First, the critical temperatures of LPSE (wet) and LPSE (dry) were measured. The experimental results revealed that LPSE (dry) operated at 100 °C, whereas LPSE (wet) operated at 65 °C. Thus, in this study, LPSE (wet) can be operated at a critical temperature 35 °C lower than that of LPSE (dry). The LPSE (wet) could be operated continuously for 900 min, demonstrating the effectiveness of the water-absorbing wick mechanism for long-duration operation. Next, the specific acoustic impedance distribution, the phase difference between the pressure and the cross-sectional mean velocity distribution, and the acoustic power distribution inside the device were measured for LPSE (dry) and LPSE (wet) during each operation. The results confirmed that both LPSE (dry) and LPSE (wet) realized a traveling wave field in which the phase difference between the pressure and cross-sectional mean velocity was close to zero and the specific acoustic impedance more than 30 times the characteristic impedance of a sound wave propagating in free space, which are required to obtain high thermal efficiency, near the regenerator position. The ratio of acoustic power before and after the regenerator was 1.18 (at a hot end temperature of 130 °C) for LPSE (dry) and 1.54 (at a hot end temperature of 90 °C) for LPSE (wet). Under the same conditions, the acoustic power of LPSE (wet) was 10 times or above that of LPSE (dry). These results confirmed that LPSE (wet) designed in this study could operate at lower temperatures and exhibit higher-power output than LPSE(dry).

Non-contact rotation of a small object using a combination of ultrasound standing and traveling waves

Noncontact transportation and separation techniques using airborne ultrasound are attractive for use in industrial fields in which micrometer- to millimeter-sized objects can be levitated, rotated, and transported in the air using acoustic standing-wave and traveling-wave fields. This paper discusses a method to rotate a small object in the air without physical contact using ultrasound. The experimental system comprises a vibrating disk with four bolt-clamped Langevin-type ultrasound transducers and two semicircular reflectors. The flexural vibration of the disk generates an acoustic standing wave between them, and a small object can be levitated at the nodal position. An acoustic traveling wave was generated in the horizontal direction in an asymmetric acoustic field by inclining one of the two reflectors, which induced rotation of the object in the clockwise or counterclockwise direction. The acoustic intensity in the circumferential direction acting on the object was then calculated, and the directions of rotation predicted by the calculations corresponded with the experimental results. Higher input currents produced higher rotation speeds; the rotation speed reached a maximum value of 6.8 ± 0.9 rps at an input current of 1.1 App.

Improved experimental scheme for the generation of pair coherent state in traveling-wave optical fields

Abstract Pair coherent state (PCS) is a two-mode non-Gaussian state recently generated within spatially confined superconducting cavities. Under typical conditions, it is unsuitable for performing global quantum missions in open space. Several methods have been proposed to generate this state with the capability to propagate unrestrictedly. However, these methods employed an excessive amount of unnecessary physical resources or relied on coherent displacement within the low regime. This paper presents a novel experimental approach to generate this state, specifically designed for facilitating long-distance quantum information processing and communication tasks. The method involves the utilization of two weak cross-Kerr nonlinear media, two balanced beam splitters, and an on/off photodetector. Furthermore, the input comprises three CSs with high amplitudes. These physical resources are potentially accessible within existing technology. The analysis of success probability and fidelity demonstrates that the PCS can be successfully generated with a high coherent parameter amplitude, even in scenarios where the photodetector efficiency is low, provided that the coherent amplitudes are sufficiently high.

Efficient control of high-precision three-dimensional atom localization via probe absorption in a five-level phase-coherent atomic system

We propose a new scheme for high-precision three-dimensional (3D) atom localization by observing the spatially modulated absorption of a weak probe field operating in a partially closed-loop dependent five-level atomic system. Different spatial structures of localization patterns are presented by controlling the Rabi frequency, detuning, and field-induced collective phase-coherence with a variety of superposed standing wave field configurations. Our results highlight that 100% detection probability of atom is possible in the present model in many ways with high precision measurement of spatial absorption. It has been shown that, in the presence of standing wave fields, position information of the atom with maximum detection probability can be efficiently controlled by employing the travelling-wave field in the system. In the present work, we note that the maximum detection probability of the atom is attainable with the limit of spatial resolution better than λ/50. The efficacy of the present model is to find its application in atom nanolithography and atom-imaging having importance in quantum information processing.

Vortex beam induced spatial modulation of quantum-optical effects in a coherent atomic medium

We have studied two-dimensional absorption, gain, and corresponding refractive index profiles in a ladder-type three-level atomic system interacting with three coherent fields. One is a weak probe field considered as a plane wave, while the other two are the control fields taken as two Laguerre–Gaussian doughnut beams. Position dependence of two vortex beams induces the spatially modulated coherence at the condition of resonance, which enables us to obtain space-dependent absorption, transparency, gain without inversion (GWI), and refractive index enhancement in the present scheme. The azimuthal modulation of coherence effects is attributed to the presence of optical angular momentum of the vortex beams. Under the influence of an additional travelling wave field with the presence of two vortex beams, the present model leads us to obtain an ultra-large enhancement of refractive index at the resonant detuning of the fields. This phenomenon makes the atom-field system to play the equivalent role of a high-refractive-index prism. The role of near dipole–dipole (NDD) interaction on the modulation of position-dependent coherence effects has also been investigated. It has been shown that, without any inclusion of the travelling wave field in the system, the phenomenon of resonant enhancement of refractive index may also occur in the presence of NDD effect. The new way of generating spatially controlled GWI and nonlinear refractive index enhancement is specific to the present model. This work seems to be useful for finding its applications in spatially modulated coherence controlled electromagnetically induced transparency-based quantum devices like quantum optical memory, switches, and quantum logic gates, where the refractive index switching phenomenon is a prerequisite.

Nonreciprocal Dissipation Engineering via Strong Coupling with a Continuum of Modes

Optical nonreciprocity plays a key role in almost every optical system, directing light flow and protecting optical components from backscattered light. Controllable forms of on-chip nonreciprocity are needed for the robust operation of increasingly sophisticated photonic integrated circuits (PICs) in the context of classical and quantum computation, networking, communications, and sensing. However, it has been challenging to achieve wideband, low-loss optical nonreciprocity on-chip. In this paper, we demonstrate strong coupling and Rabi-like energy exchange between photonic bands, possessing a continuum of modes, to unlock nonreciprocity and frequency translation over wide optical bandwidths in silicon. Using a traveling-wave phonon field to drive indirect interband photonic transitions, we demonstrate band hybridization that enables an intriguing form of nonreciprocal dissipation engineering. Using the converted mode to create a nonreciprocal dissipation channel, we demonstrate a frequency-neutral, low-loss (less than 1 dB) isolator with high nonreciprocal contrast (more than 14 dB) and broad operating bandwidth (more than 59 GHz). Additionally, through the implementation of complete interband conversion, we demonstrate a high extinction (more than 55 dB) optical frequency translation operation with near-unity efficiency. Published by the American Physical Society 2024

RETRACTED: Impact of High-Frequency Traveling-Wave Magnetic Fields on Low-Conductivity Liquids: Investigation and Potential Applications in the Chemical Industry.

High-frequency traveling-wave magnetic fields refer to alternating magnetic fields that propagate through space in a wave-like manner at high frequencies. These magnetic fields are characterized by their ability to generate driving forces and induce currents in conductive materials, such as liquids or metals. This article investigates the application and approaches of a unique form of high-frequency traveling-wave magnetic fields to low-conductivity liquids with conductivity ranging from 1 to 102 S/m. Experiments were conducted using four representative electrolytic solutions commonly employed in the chemical industry: sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium chloride (NaCl), and ionic liquid ([Bmim]BF4). The investigation focuses on the impact of high-frequency magnetic fields on these solutions at the optimal operating point of the system, considering the effects of Joule heating. The findings reveal that the high-frequency traveling magnetic field exerts a significant volumetric force on all four low-conductivity liquids. This technology, characterized by its non-contact and pollution-free nature, high efficiency, large driving volume, and rapid driving speeds (up to several centimeters per second), also provides uniform velocity distribution and notable thermal effects. It holds considerable promise for applications in the chemical industry, metallurgy, and other sectors where enhanced three-phase transfer processes are essential.

Способ повышения помехозащищённости пожарного извещателя пламени

Introduction. Increasing the safety of objects for various purposes requires constant improvement of fire detection means for their most effective use in specific conditions. The main objective of research and development in this area is to improve detectors that provide early fire detection with high noise immunity during operation. To a large extent, this is achieved by using a combination of the various associated factors that can be detected and the principles of detector design. Goals and objectives. The purpose of the article is to substantiate the possibility of increasing the noise immunity of a fire detector using a new combination of associated factors and methods for their detection. Methods. System analysis methods and fire detection methods using various physical principles were used. Results and discussion. Based on an analysis of the physical principles of fire detection, it is shown that light and ultrasonic detection methods are similar in characteristics for detecting typical fires TP1, TP4-TP6, which have significant burning intensity and strong heat flows. In addition, devices that respond to light (electromagnetic) radiation from a flame and reflection of ultrasonic waves are of interest as potentially the fastest ones. The fire detector proposes a combination of a passive light channel operating in the ultraviolet frequency band and an active ultrasonic surface channel using a traveling wave field. The structural diagram of a combined fire detector designed to detect open fires is considered. Possible technical characteristics and application features of the proposed detector are presented. Conclusions. The presented principle of forming a combined fire detector can be used in practice, ensuring increased stability of operation during operation under conditions of natural and man-made interference, accompanied by electromagnetic radiation. An additional advantage of such a detector is the preservation of high performance, which is necessary to solve the problem of early fire detection by a fire alarm system while ensuring fire protection of objects. Key words: facility safety; fire alarm; fire factors; flame detector; combined detector.

Phase holograms for the three-dimensional patterning of microparticles in a traveling wave field

Acoustic fields can generate radiation forces that can align particles in patterns. Forces from standing waves pattern particles in three dimensions (3-D) at either nodal or anti-nodal regions. These patterns can be utilized to form 3-D microstructures for applications in tissue engineering or fabrication of layered materials. However, standing waves require more than one transducer or a reflector, which can complicate implementation. Here, we developed a method to suspend and align microspheres using a traveling wave from a single transducer. Acoustic fields were shaped to align polyethylene microspheres mimicking tissue cells in parallel planes along the axis of the transducer. A Bessel-like beam was developed using diffraction theory and an iterative angular spectrum approach were used to design phase holograms to shape pressure fields. Gor’kov potential was used to calculate radiation forces while minimizing the axial forces to create a stable trap. The resulting pressure fields and particle patterns matched predictions with a similarity index >0.92, where 1 is a perfect match. The transverse radiation force was ten times each microsphere’s weight and comparable to the standing wave radiation forces. Next steps are in vivo implementation of cell patterning for tissue engineering. [Work supported by NIH K25-DK132416 and P01-DK043881.]

Synthetical performance analysis of phase-change thermoacoustic regenerators and stacks

Introducing a phase-change component to thermoacoustic regenerators or stacks increases the complexity of the thermoacoustic conversion process, and currently the analysis of relevant influencing factors is still limited. This paper introduces a comprehensive analysis method for wet regenerators or stacks by deriving normalized parameters, including acoustic power, efficiency, and temperature gradient. The analysis encompasses various influencing factors and impedance phases, revealing that the mass diffusion process enhances performance and lowers the onset threshold. Optimized wet regenerators with a traveling-wave field exhibit an efficiency 0.239 higher than that of dry regenerators, and their acoustic power surpasses dry regenerators by a maximum factor of 41.8. Additionally, the required length ranges and hydraulic radius for onset become more extensive. Furthermore, the onset temperature gradient decreases greatly, in a standing-wave system, wet stacks achieve a minimum temperature gradient 0.27 times that of dry stacks. The mass diffusion process augments the degree of reversibility in wet regenerators. Optimized wet regenerators tend to achieve high performance with smaller radius and impedance phases closer to 0° compared to the dry ones. This research offers valuable insights for designing, analyzing, and optimizing wet thermoacoustic regenerators or stacks.

Effect of traveling-wave magnetic field on dendrite growth of high-strength steel slab: Industrial trials and numerical simulation

Effect of traveling-wave magnetic field on dendrite growth of high-strength steel slab: Industrial trials and numerical simulation

Insulating traveling-wave electrophoresis.

Traveling-wave electrophoresis (TWE) is a method for transporting charged colloidal particles used in many microfluidic techniques for particle manipulation and fractionation. This method exploits the traveling-wave components of the electric field generated by an array of electrodes subjected to ac voltages with a phase delay between neighboring electrodes. In this article, we propose an alternative way of generating traveling-wave electric fields in microchannels. We apply a rotating electric field around a cylindrical insulating micropillar and the resulting traveling-wave modes induce particle drift around the cylinder. We term this phenomenon insulating traveling-wave electrophoresis (i-TWE) to distinguish it from standard TWE performed with arrays of microelectrodes. We characterized the particle drift experimentally and show a quantitative comparison of the particle velocity with theoretical predictions. Excellent agreement is found when the influence of electro-osmosis on the channel walls is also considered.

Sustainable irrigation of pipeline fluid flow rate regulation based on traveling wave magnetic field

To adjust the flow rate of liquid in the pipeline in real-time in the process of crop drip irrigation, to achieve sustainable agricultural irrigation. This paper designs and develops a kind of liquid speed-regulating device for drip irrigation based on traveling wave magnetic field. This paper aims to use the electromagnetic driving force generated by the traveling wave magnetic field to realize the soft control of liquid flow rate in drip irrigation pipelines. First of all, the structure of the combined traveling wave magnetic field generator was designed. COMSOL physical field simulation software was used to build the traveling wave magnetic field simulation model, and the magnetic field distribution diagram and the variation curve of the magnetic field intensity were generated in the time domain. Then, through the analysis of the simulation model, the harmonic interference of a single row and combined traveling-wave magnetic field generator is compared, and the optimal spacing between the traveling-wave magnetic field generator units is determined. Finally, the water-fertilizer fusion liquid used in the process of agricultural irrigation was selected and the liquid speed regulation experiment was carried out. The experimental results show that the combined liquid speed regulating device can effectively reduce the number of traveling wave field harmonics, compared with the single wave field generator at the same power, the magnetic field intensity is increased by 33.9 %. When the excitation current is 2 A and the initial flow rate is 0.5 m/s, the device can increase the flow rate of water-fertilizer fusion liquid for agricultural drip irrigation by 2.27 % and decrease by 2.13 %, which can meet the real-time and effective speed regulation requirements of water-fertilizer fusion liquid in the process of agricultural drip irrigation.

Measurements of velocity-selective resonances from adiabatic rapid passage

The authors measure the velocity dependence of applied optical forces on a metastable He atom beam. The optical force implemented using adiabatic rapid passage shows unexpected, equally spaced peaks in velocity space. Such resonances may result from coherence established by atomic motion in traveling-wave laser fields.

Doppler-free spectroscopy of an atomic beam probed in traveling-wave fields

The authors propose and demonstrate a method for precision spectroscopy of atoms in a beam using two sequential rather than simultaneous laser pulses, thereby overcoming systematic challenges associated with standing-wave beams that plague other methods. Their results show that this method can effectively suppress the first-order Doppler effect and reduce systematic uncertainty.

Key Space Enhancement in Chaotic Secure Communication Utilizing Monolithically Integrated Multi-Section Semiconductor Lasers

Chaotic secure communication schemes encounter a conflict of key space enhancement between the consistency and complexity of chaotic transceivers. In this paper, we propose a monolithically integrated multi-section semiconductor laser (MIMSL), used as a compact chaotic transceiver with an enhanced key space. The MIMSL consists of a distributed feedback (DFB) laser section, a semiconductor optical amplifier (SOA) section, two phase (P) sections and a passive optical waveguide. We simulate the dynamics of the MIMSL by applying the time-dependent coupled-wave equations for traveling-wave optical fields. Further, we numerically demonstrate a security enhancement of the unidirectional chaotic communication scheme using the MIMSL transceivers with independent high-speed modulation in the phase sections of the MIMSL. The security of our scheme depends not only on the difficulty of identifying the MIMSL structural parameters and the bias current of each section, but also on the phase shifts in two phase sections providing the additional dimension of security key space. Final simulation results show that a total of 248 key spaces can be achieved with a data rate of 2.5 Gb/s and an injection strength of 0.36.

Two-dimensional electromagnetically induced grating via phase regulation in a closed-loop four-level atomic system

We proposed a theoretical scheme for two-dimensional (2D) electromagnetically induced grating (EIG) in a closed-loop four-level atomic system driven by a weak probe field, a traveling-wave control field, two orthogonal standing-wave fields and a microwave field. Due to low amplitude modulation accompanied with large phase modulation, EIG can be obtained and the probe energy can be diffracted into first-order and even high-order directions with high efficiency. The results show that the diffraction pattern and efficiency of the EIG could be adjusted effectively by the probe field detuning, the coherent field intensity, the interaction length. Meanwhile, the quantum interference between the amplitude modulation and phase modulation can be manipulated by the relative phase, which can be used to regulate the diffraction pattern and efficiency of the 2D EIG. Our scheme of 2D EIG may be useful in beam splitting and all-optical switching.

Active control of heat transport inside the porous material of a looped-tube dual-acoustic-driver thermoacoustic refrigerator

Compared with passive control approaches, it is more convenient to control the heat transport within the porous material of electrically-driven thermoacoustic refrigerators (TARs) by actively modulating the operating parameters of the acoustic driver(s). This study concentrates on the heat transport within the porous material of a looped-tube TAR driven by two acoustic drivers. Analytical models based on the linear theory are established to describe the acoustic field inside the TAR and the temperature field within the porous material. It is found that the heat transport within the porous material of the looped-tube TAR can be modulated by changing the driving frequency, phase difference and positions of acoustic drivers. The resonance frequencies of the looped-tube TAR are not affected by the phase difference but are influenced by the positions of acoustic drivers. Different from thermally-driven TARs that prefer a traveling-wave acoustic field, electrically-driven TARs should operate at resonance frequencies at which a standing wave dominates, and most of the work input from the acoustic drivers is used to pump heat. To achieve a large temperature difference, the two acoustic drivers should be placed asymmetrically at two sides of the porous material. This study offers a generic theoretical framework to investigate electrically-driven TARs with one or multiple porous materials and acoustic drivers, providing useful guidelines for the development of high-performance TARs as a green technology in low-temperature engineering.

Chirality-switchable acoustic vortex emission via non-Hermitian selective excitation at an exceptional point

Artificial structures provide an efficient method to generate acoustic vortices carrying orbital angular momentum (OAM) essential for applications ranging from object manipulation to acoustic communication. However, their flexibility in terms of chirality control has thus far been limited by the lack of reconfigurability and degrees of freedom like spin–orbit coupling. Here we show that this restriction can be lifted by controlling the individual on–off states of two coherent monopolar sources inside a passive parity-time-symmetric ring cavity at an exceptional point where the counter-propagating waves coalesce into one chiral eigenmode. One of the sources satisfies the chirality-reversal condition, generating a travelling wave field fully decoupled from and opposite to the chiral eigenmode, while the other source is phase-shifted such that the wave generated by the first source can be canceled out, and the remaining sound field circulates in the same direction as the chiral eigenmode. Such non-Hermitian selective excitation enables our experimental realization of acoustic vortex emission with switchable OAM but free of system reconfiguration. Our work offers opportunities for chiral sound manipulation as well as integrated and tunable acoustic OAM devices.

Theoretical performance characteristics of a travelling-wave phase-change thermoacoustic heat pump

Thermoacoustic technology is a promising approach for environmentally-benign, low-cost heat pumping. Herein, we present a theoretical investigation on phase-change thermoacoustic heat pumping employing both an ideal model (a short heat pump in a pure travelling-wave field), as well as a full-size, looped-tube thermoacoustic heat pump. In the analysis of the short heat pump, we identified and assessed the main factors and their influence on the performance of an ideal phase-change travelling-wave heat pump. The results show that, ideally, the cooling power can be significantly increased by up to one order of magnitude, and the COP (coefficient of performance) can also be improved by the incorporation of phase change into the thermoacoustic cycle. Meanwhile, the analysis of the full system provides a more practical view of the enhancement due to phase change. A significant increase of cooling power is observed in the phase-change system with a high concentration of the reactive component, but increased of the COP only occurs under small temperature differences (below 10 K). The main reason for the gap in observed performance between the ideal model and the full system is the deviation, under a large temperature difference, of the acoustic field from the requirements for effective enhancement, as revealed in the ideal model. Our results demonstrate the potential of the phase-change travelling-wave thermoacoustic heat pump for efficient and low-cost heat pumping, especially for small temperature difference applications.