Parametric Conversion Research Articles

Terahertz parametric upconversion detection based on KTiOAsO4 crystal

Terahertz parametric upconversion detection based on KTiOAsO4 crystal

Analysis of Global Design Standards to Assess Different Levels of Structural Seismic Protection

ABSTRACT This research undertakes a thorough examination of the significant social and economic losses resulting from earthquakes throughout time, as well as the considerable destruction inflicted upon physical structures. Using the reinforced concrete frame structure as an illustration, it highlights several types of column damage that might potentially happen to the structure during seismic events. As cross-border projects become more frequent, it is crucial to have precise specification comparisons and parameter conversions as a reference for engineering projects happening worldwide. This article will now analyze and contrast the seismic building designs of China, the United States, Indonesia, and Australia. These nations are selected based on their susceptibility to earthquakes, with China, the United States, and Indonesia being earthquake-prone, while Australia has infrequent seismic activity. An assessment of each country’s standards is undertaken, specifically parameters in relation to seismic defence standards, seismic protection levels, method of determining shear wave velocity, method of determining site subsoil and the implementation of the seismic design response spectrum. An evaluation was made after analyzing each parameter based on the requirements in the standards, and a recommendation for the most practical and reasonable method from one of the countries for each parameter was provided. Overall, seismic standards from China were deemed the most thorough and considerate standard, which not only encompassed a broader range for each parameter but was also deemed the most technical and considerate in terms of parameter derivation.

DEVELOPMENT OF ADJUSTABLE TAPERED AEROSTATIC BEARINGS FOR NON-CONTACT DIRECT MACHINE DRIVES

The article is devoted to making adjustable conical air bearings. Its application in different machines allows increase load capacity and reliability, speed extension, reduce mass, overall dimensions and air consumption, secure stable rotary motion in speed wide range due to adjustment of static and dynamic characteristics of direct drives. Mathematical models of single-support and multi-support systems have been designed for study of its characteristics and efficiency of suggested improvements. Function relations between structural, functional, geometric parameters of conical aerostatic systems have been theoretically determined for adjustable air gap that allows change load capacity and dynamic characteristics of non-contact direct drives. Method of parametric conversion of conical bearings to radial and thrust bearings has been suggested. It gives analytical solution of non-contact drive static characteristics. Analytical stability criterion of rotor of single-support system has been determined. Working capacity conditions have been analytically obtained from mass and inertial properties, parameters and characteristics of air-bearing direct drive. Adjustable conical air-bearing pneumatic spindle has been manufactured. Experimental set-up and experimental technique have been designed for validation theoretical results. Design procedure of air-bearing non-contact drives has been engineered. Algorithm of numerical experiment of static characteristics and dynamic properties has been engineered for design decision verification.

An acoustic metamaterial with space-time modulated densitya).

Space-time modulation opens the door for unprecedented wave behavior control, such as nonreciprocal wave manipulation. Here is proposed a one-dimensional space-time modulated membrane system aiming to realize a kind of acoustic metamaterial with space-time modulated effective density. Three different approaches, namely, the effective medium method, transfer matrix method, and time-domain simulation, are applied to analyze the acoustic response of the system under a monochromatic incidence. Results show that the proposed metamaterial can support two different nonreciprocal acoustic functionalities, namely, unidirectional parametric amplification and parametric frequency conversion, when different modulation profiles are enforced.

Conversion, prediction, and application of strength and stiffness parameters for grouted reconstructed rock mass

Ultrasonic detection has emerged as a rapid method for acquiring rock mass sound velocity and converting it into an elastic modulus parameter, a pivotal technique for investigating the in-situ mechanical properties of rock masses. Despite its significance, accurately deducing rock mass strength from elastic modulus remains a formidable challenge and a pressing issue in the realm of protorock parameter research. This study introduces an innovative artificial intelligence-driven methodology for transforming elastic modulus and strength parameters specific to coal measures through rigorous data analysis and experimental validation. By integrating two illustrative engineering cases, we explore the complexities of water inrush and floor heave issues encountered in tunnels traversing fault zones. The novel strength parameter calculation approach is benchmarked against previous studies, highlighting its superior advantages in terms of effectiveness and applicability. In essence, this research offers a comprehensive framework and practical workflow for translating in-situ acoustic parameter-derived elastic modulus into rock mass strength, serving as a valuable resource for future endeavors in mine water control research.

Parametrically controlled microwave-photonic interface for the fluxonium

Converting quantum information from stationary qubits to traveling photons enables both fast qubit initialization and efficient generation of flying qubits for redistribution of quantum information. This conversion can be performed using cavity-sideband transitions. In the fluxonium, however, direct cavity-sideband transitions are forbidden due to parity symmetry. Here we circumvent this parity selection rule by using a three-wave mixing element to couple the fluxonium to a resonator. We experimentally demonstrate a scheme for interfacing the fluxonium with traveling photons through microwave-induced parametric conversion. We perform fast reset on the fluxonium qubit, initializing it with >95% ground-state population. We then implement controlled release and temporal shaping of a flying photon, useful for quantum state transfer and remote entanglement. The simplicity and flexibility of our demonstrated scheme enables fluxonium-based remote entanglement architectures. Published by the American Physical Society 2024

A multiscale model for efficiently simulating laser powder bed fusion process with detailed microstructure and mechanical performance results

Numerical simulation is regarded as an important method for studying the mechanisms of additive manufacturing (AM), especially in building a multiscale simulation model. However, the conversion of physical phenomena and parameters across scales is complex, and the number of simulation elements often changes extremely, leading to an inherent conflict between simulation accuracy and efficiency. Therefore, this work introduces a model that balances the need for detailed grain morphology and overall simulation efficiency, to investigate the relationship between process parameters, microstructure, and mechanical performance during Inconel 718 laser powder bed fusion (L-PBF) process. The cellular automata - finite element method (CA-FEM) was used to simulate the melt pool forming and predict the microstructure evolution. Based on the CA result, the tensile process was simulated through crystal plasticity-finite element method (CP-FEM). Specially, the CA-FEM model was simplified and sliced layer-by-layer to reduce simulation time and data storage, supporting parallel computation. The prediction time for the microstructure growth of millions of elements was less than 1.5 h. The CP-FEM model was simplified by reasonably reducing elements in the representative volume element (RVE) model, improving the simulation efficiency by 73 %. The simulation results were validated through EBSD observation and tensile tests, showing good agreement with experimental results, with the final simulation error for mechanical performance not exceeding 10 %. The effects of process parameters on microstructure and mechanical performance were comprehensively discussed. This model supports the optimization of L-PBF process parameters for Ni-based alloys and provides a reference for improving the efficiency of multiscale simulations for other AM processes and materials.

High-efficiency mid-infrared CW-seeded optical parametric generation in PPLN waveguide.

Mid-infrared optical sources have been extensively used in a variety of applications, including gas sensing and metrology, by exploiting the fingerprint fundamental vibrational absorption bands of molecules in this spectral region. Parametric frequency conversion techniques, such as optical parametric generation (OPG) and optical parametric oscillator (OPO), represent common methodologies for mid-infrared generation. Notably, continuous-wave (CW)-seeded OPG exhibits superior stability and performance compared to conventional OPG. Here, we present a simple method for mid-infrared source generation based on femtosecond OPG in periodically poled lithium niobate (PPLN) waveguides. In addition to its robustness and simplicity, mid-infrared CW-seeded OPG features a high quantum conversion efficiency of 46.5% and a low threshold. The phase of CW-seeded OPG was passively referenced to the CW laser, making it suitable for dual-comb applications. This system shows great promise in the miniaturization of mid-infrared combs and will be applied to non-laboratory applications, including open-path atmospheric gas sensing and portable environmental monitoring.

Powerful Electronic Systems for Conversion of Parameters of Electrical Energy with Nonlinear Pulse-Width Regulation of the Output Voltage

Powerful Electronic Systems for Conversion of Parameters of Electrical Energy with Nonlinear Pulse-Width Regulation of the Output Voltage

Compact 2-μm Hundred Hertz optical parametric oscillator Based on KTP crystal

A 100 Hz compact 2 μm optical parametric oscillator (OPO) based on a type II non-critically phase-matched KTiOPO4 crystal (KTP) was reported. The monolithic KTP crystal was pumped with a passively Q-switched 1064 nm Nd:YAG laser. At a repetition rate of 100 Hz and a single pulse energy of 5.8 mJ of pump light, a 2128-nm laser output was achieved with a maximum of 1.17 mJ of parametric light at the degenerate point, with a parametric light pulse width of approximately 10.5 ns, corresponding to a pump to parametric light conversion efficiency of 20.1 %.

Improving the experimental estimation of the incident angle modifier of evacuated tube solar collectors with heat pipes

This article focuses on the thermal performance testing of evacuated tube solar collectors with heat pipes (ETC-HP) using the ISO 9806:2017 standard test methods: Steady-state testing (SST) and Quasi-dynamic testing (QDT). The main objective of this work is to improve the experimental estimation of the incident angle modifier (IAM) for these types of solar collectors in both test methods. For the QDT method, a novel model for the IAM is presented and validated against SST results. This IAM model, recently developed for flat plate collectors under the SST framework, has demonstrated superior performance compared to other available models. This study marks its first application to ETC-HP technology, showcasing its adaptability across different technologies and test methods. While this work primarily focuses on ETC-HP collectors, the results are applicable to evacuated tubes in general. Thus, the generality of this model and its consistency with the SST method make it suitable for implementation in test standards as a general-purpose model. Regarding the SST method, and aiming to enhance consistency between testing methods, an improved parameter conversion from SST to QDT is also proposed, reducing IAM differences between test methods by 1 to 19 percentage points, with greater improvement at higher incidence angles.

Analysis of strength size effect and failure mechanism of asphalt mixtures based on discrete element method

The purpose of this study is to further investigate the strength size effect and failure mechanism of asphalt mixtures and clarify the strength parameter conversion relationship between standard and non-standard size samples. The article established an improved microscopic model for uniaxial compression and indirect tensile testing of asphalt mixtures based on laboratory and discrete element simulation tests. The effects of thickness and gradation on the uniaxial compressive strength (UCS) and indirect tensile strength (ITS) of asphalt mixtures were studied. The loading rates of the UCS and ITS tests were set at 2 mm/min and 50 mm/min, respectively. Additionally, the tensile-compressive stress distribution, crack propagation, and strength contribution rates of different contact types within the sample were investigated during the virtual model loading process. The reliability of the model was validated through laboratory test results. Finally, the strength parameter conversion relationship between standard and non-standard size samples was investigated. The study found that the UCS of asphalt mixtures decreases with increasing thickness, while the ITS increases with increasing thickness, with average reduction and increase rates of 70.69 % and 24.18 %, respectively. The contact fracture ratio and the strength contribution rate of the aggregate-asphalt mortar contacts both exceed 50 %, indicating that the fracture of these contacts is the primary cause of asphalt mixture failure. The use of small-sized samples instead of standard samples in practical applications is promising. These research work outcomes can serve as a theoretical basis for designing asphalt pavement materials and acquiring existing asphalt pavement material parameters.

УЗАГАЛЬНЕННЯ ОСНОВНИХ ПОЛОЖЕНЬ ДЕКОМПОЗИЦІЇ ТРАНСФОРМАТОРНО-КЛЮЧОВИХ ВИКОНАВЧИХ СТРУКТУР РЕГУЛЯТОРІВ НАПРУГИ З ДИСКРЕТНО-РАЗОВИМ КЕРУВАННЯМ НАПІВПРОВІДНИКОВИМИ ЕЛЕМЕНТАМИ

Executive structures of a significant part of voltage regulators in systems of conversion of electricity parameters are based on the integration of semiconductor switch and transforming elements (SE and TE, respectively). In particular, these are transformer-and-switches executive structure (TSES), in which the TE windings are sectioned in a certain way or have intermediate taps with key elements connected to them. Discrete-time control of these KEs makes it possible to realize the operation of TSES in a set of operating states with corresponding voltage transfer coefficients. The purpose of the work was to generalize the main provisions of improving TSES voltage regulators through their decomposition (separation into separate control units) in order to ensure high efficiency of semiconductor devices and reduce their losses. The peculiarities of the decomposition of TSES during the regulation of alternating and rectified current voltage are analyzed. Expedient depths of decomposition are determined. It has been proven the operation of reformatting sec-tions in control units, subject to compliance with the optimal laws of sectioning of the winding, ensures the necessary efficiency of the use of SE. Recommendations are given on the areas of implementation of rectified current voltage regulators. References 7, tables 3, figures 3.

Visual Perception and Multimodal Control: A Novel Approach to Designing an Intelligent Badminton Serving Device

Addressing the current issue of limited control methods for badminton serving devices, this paper proposes a vision-based multimodal control system and method for badminton serving. The system integrates computer vision recognition technology with traditional control methods for badminton serving devices. By installing vision capture devices on the serving device, the system identifies various human body postures. Based on the content of posture information, corresponding control signals are sent to adjust parameters such as launch angle and speed, enabling multiple modes of serving. Firstly, the hardware design for the badminton serving device is presented, including the design of the actuator module through 3D modeling. Simultaneously, an embedded development board circuit is designed to meet the requirements of multimodal control. Secondly, in the aspect of visual perception for human body recognition, an improved BlazePose candidate region posture recognition algorithm is proposed based on existing posture recognition algorithms. Furthermore, mappings between posture information and hand information are established to facilitate parameter conversion for the serving device under different postures. Finally, extensive experiments validate the feasibility and stability of the developed system and method.

Topologically Protected Parametric Wavelength Conversion in a Valley Hall Insulator

AbstractNonlinear phenomena are investigated in a topological photonic valley Hall insulator (VHI) using a Kagome system designed to have localized topological boundary state (TBS) at telecommunications wavelengths. Valley Hall topologically protected nonlinear phenomena are demonstrated. Similar transmission properties and parametric wavelength conversion of up to −12 dB are experimentally achieved using sub‐milliwatt average powers in a zigzag interface without back‐scattering, compared with a straight interface. Furthermore, a 7 dB slow light enhancement is observed in the conversion efficiency near the red edge in the transmission band of the boundary state, demonstrating how slow light‐induced backscattering may be circumvented by leveraging the topologically protected boundary state. A Kerr‐induced delocalization of the valley Hall topological state (VHTS) is further experimentally observed, which can be harnessed to control the properties of topological edge states.

Impact of pump-phase noise in PPLN-based optical parametric amplifier and wavelength converter for digital coherent transmission

Wideband signal amplification and optical signal processing with a high gain using an optical parametric amplifier based on a periodically poled LiNbO3 (PPLN) waveguide is attractive for constructing wideband optical fiber networks. We experimentally investigate the transfer characteristics of the phase noise of a pump laser in χ(2)-based optical parametric amplification and wavelength conversion on the basis of second-harmonic-generation and differential-frequency-generation processes. We also evaluate the effect of the transferred phase noise on signal quality in dispersion-unmanaged digital coherent fiber transmission systems. We show that the phase noise is transferred only to the wavelength-converted idler and does not affect the amplified signal even by using a pump laser with a MHz-order linewidth. We also show that the phase noise transferred to the idler light can have a similar impact on signal quality as equalization-enhanced phase noise (EEPN) in digital coherent transmission. The signal penalty including EEPN was evaluated with several pump lasers and at symbol rates of 32, 64, and 96 Gbaud. We also propose a method of using correlated pump lights between a wavelength converter pair to cancel out the transfer of phase noise.

Investigating the effects of sum-frequency conversions and surface impedance uniformity in traveling wave superconducting parametric amplifiers

Traveling wave parametric amplifiers (TWPAs) offer the most promising solution for high gain, broadband, and quantum noise limited amplification at microwave frequencies. Experimental realization of TWPAs has proved challenging with often major discrepancies between the theoretically predicted and the measured gain performance of the devices. Here, we extend the conventional modeling techniques to account for spatial variation in the surface impedance of the thin film and the parametric sum-frequency conversions effect, which subsequently results in accurate reproduction of experimental device behavior. We further show that such an analysis may be critical to ensure fabricated TWPAs can operate as designed.

Zeptojoule detection of terahertz pulses by parametric frequency upconversion.

We combine parametric frequency upconversion with the single-photon counting technology to achieve terahertz (THz) detection sensitivity down to the zeptojoule (zJ) pulse energy level. Our detection scheme employs a near-infrared ultrafast source, a GaP nonlinear crystal, optical filters, and a single-photon avalanche diode. This configuration is able to resolve 1.4 zJ (1.4 × 10-21 J) THz pulse energy, corresponding to 1.5 photons per pulse, when the signal is averaged within only 1 s (or 50,000 pulses). A single THz pulse can also be detected when its energy is above 1185 zJ. These numbers correspond to the noise-equivalent power and THz-to-NIR photon detection efficiency of 1.3 × 10-16 W/Hz1/2 and 5.8 × 10-2%, respectively. To test our scheme, we perform spectroscopy of the water vapor between 1 and 3.7 THz and obtain results that are in agreement with those acquired with a standard electro-optic sampling (EOS) method. Our technique provides a 0.2 THz spectral resolution offering a fast alternative to EOS THz detection for monitoring specific spectral components in spectroscopy, imaging, and communication applications.

Wide-field mid-infrared hyperspectral imaging beyond video rate

Mid-infrared hyperspectral imaging has become an indispensable tool to spatially resolve chemical information in a wide variety of samples. However, acquiring three-dimensional data cubes is typically time-consuming due to the limited speed of raster scanning or wavelength tuning, which impedes real-time visualization with high spatial definition across broad spectral bands. Here, we devise and implement a high-speed, wide-field mid-infrared hyperspectral imaging system relying on broadband parametric upconversion of high-brightness supercontinuum illumination at the Fourier plane. The upconverted replica is spectrally decomposed by a rapid acousto-optic tunable filter, which records high-definition monochromatic images at a frame rate of 10 kHz based on a megapixel silicon camera. Consequently, the hyperspectral imager allows us to acquire 100 spectral bands over 2600-4085 cm−1 in 10 ms, corresponding to a refreshing rate of 100 Hz. Moreover, the angular dependence of phase matching in the image upconversion is leveraged to realize snapshot operation with spatial multiplexing for multiple spectral channels, which may further boost the spectral imaging rate. The high acquisition rate, wide-field operation, and broadband spectral coverage could open new possibilities for high-throughput characterization of transient processes in material and life sciences.

Over 3.8 W, 3.4 µm picosecond mid-infrared parametric conversion based on a simplified one-to-many scheme

In this paper, we demonstrate a simplified one-to-many scheme for efficient mid-infrared (MIR) parametric conversion. Such a scheme is based on a continuous wave (CW) single longitudinal mode master oscillator power-amplifier (MOPA) fiber system as the signal source and a picosecond pulsed MOPA fiber system, exhibiting multiple longitudinal modes, as the pump source. The signal and pump beams are combined and co-coupled into a piece of 50-mm long 5% MgO-doped PPLN crystal for the parametric conversion. As high as ∼3.82 W average power at a central idler wavelength of ∼3.4 µm is achieved when the launched pump and signal powers are ∼41.73 and ∼11.45 W, respectively. Above some threshold value, the delivered idler power shows a roll-over effect against the signal power and saturation-like effect against the pump power. Consequently, the highest conversion efficiency is observed at such a threshold pump power. To the best of our knowledge, our result represents the highest average power produced from any single-pass parametric conversion source with >3 µm idler wavelength feeding with a CW signal. Moreover, our proposed scheme can simplify the design of parametric conversion system significantly and meanwhile make the system more robust in applications. This is attributed to two main aspects. Firstly, the scheme’s one-to-many feature can reduce wavelength sensitivity remarkably in the realization of quasi-phase-matching. Secondly, for moderate power requirement it does not always require a high peak power synchronized pulsed signal source; a CW one can be an alternative, thereby making the system free from complex time synchronization and the related time jitter.