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This study presents the use of two superimposed transparent acrylic plates as a load cell for strain and force measurement. The gap between the plates behaves like an interferometer. When a monochromatic light beam is incident upon the gap, it interacts with the two air-acrylic interfaces, causing constructive and destructive interference. This phenomenon results in the formation of an interference pattern. Interferometers are devices used for high-precision measurements. In this work, the strain and force applied to an aluminum bar were precisely measured using two acrylic plates fixed to the bar. The experiments showed that the proposed method has a measurement range of 0–60 μ ε and a resolution of 0.27 μ ε. It is demonstrated that the proposed method offers a low-cost strain measurement technique with a wider measurement range compared to fiber optic sensors [ABSTRACT FROM AUTHOR]

Fiber-optic sensors, such as fiber Bragg grating (FBG) sensors and fiber-optic interferometers, have excellent sensing capabilities for industrial, chemical, and biomedical engineering applications. This paper used machine learning to enhance the number of fiber-optic sensing placement points and promote the cost-effectiveness and diversity of fiber-optic sensing applications. In this paper, the framework adopted is the FBG cascading an interferometer, and a deep belief network (DBN) is used to demodulate the wavelength of the sampled complex spectrum. As the capacity of the fiber-optic sensor arrangement is optimized, the peak spectra from FBGs undergoing strain or temperature changes may overlap. In addition, overlapping FBG spectra with interferometer spectra results in periodic modulation of the spectral intensity, making the spectral intensity variation more complex as a function of different strains or temperature levels. Therefore, it may not be possible to analyze the sensed results of FBGs with the naked eye, and it would be ideal to use machine learning to demodulate the sensed results of FBGs and the interferometer. Experimental results show that DBN can successfully interpret the wavelengths of individual FBG peaks, and peaks of the interferometer spectrum, from the overlapping spectrum of peak-overlapping FBGs and the interferometer. [ABSTRACT FROM AUTHOR]

The digital correlator is one of the most crucial data processing components of a radio telescope array. With the scale of radio interferometeric array growing, many efforts have been devoted to developing a cost-effective and scalable correlator in the field of radio astronomy. In this paper, a 192-input digital correlator with six CASPER ROACH2 boards and seven GPU servers has been deployed as the digital signal processing system for Tianlai cylinder pathfinder located in Hongliuxia observatory. The correlator consists of 192 input signals (96 dual-polarization), 125-MHz bandwidth, and full-Stokes output. The correlator inherits the advantages of the CASPER system, for example, low cost, high performance, modular scalability, and a heterogeneous computing architecture. With a rapidly deployable ROACH2 digital sampling system, a commercially expandable 10 Gigabit switching network system, and a flexible upgradable GPU computing system, the correlator forms a low-cost and easilyupgradable system, poised to support scalable large-scale interferometeric array in the future. [ABSTRACT FROM AUTHOR]

Wafer quality control is one of the important processes to improve the yield rate of semiconductor products. Profile quality and defects in the wafer are two key factors that should be taken into consideration. In this research, we introduce a method that measures the profile of the upper surface and the thickness of the wafer at the same time using an optical fiber cascaded Fabry-Pérot interferometer working at wavelength of 1550 nm. Therefore, the 3D profile of the wafer can be reconstructed directly. Testing results show that both accuracy and precision of the Fabry-Pérot interferometer are within a nanometer scale. Defects, especially those embedded inside the wafer, will be detected by monitoring the leaky field with treating wafers as slab waveguides. With the leaky field detection, defects on the lower surface of the wafer were successfully detected by monitoring the leaky field above the upper surface of the wafer. Compared with traditional methods such as radiographic testing or computed tomography testing, the proposed methods provide a cost-effective alternative for wafer quality evaluation. [ABSTRACT FROM AUTHOR]

Fiber optic pressure sensors operate on various interferometric principles, such as amplitude modulation and polarization variation. In this study, we have developed and implemented a Fabry-Pérot interferometric sensor employing an innovative technique for membrane fabrication. The sensor utilizes a μ-cavity formed at the terminus of a multimode optical fiber through a chemical etching process. The first reflecting surface is established at the interface (core/air), while the second reflection takes place at the polymeric μ-membrane within polydimethylsiloxane (PDMS), serving as the second interface (PDMS/Air). The μ-cavity exhibits dimensions of up to 63 μm in depth and 83 μm in base diameter, with a membrane thickness of approximately 6 μm. The pressure and temperature sensitivity of the sensor are measured at − 51.8 nm/KPa and 0.3 nm/°C, respectively. The performance of the developed sensor is comprehensively characterized through an analytical study and simulation employing the finite element method COMSOL. [ABSTRACT FROM AUTHOR]

The ground‐based, high‐frequency radars of the Super Dual Auroral Radar Network (SuperDARN) observe backscatter from ionospheric field‐aligned plasma irregularities and features on the Earth's surface out to ranges of several thousand kilometers via over‐the‐horizon propagation of transmitted radio waves. Interferometric techniques can be applied to the received signals at the primary and secondary antenna arrays to measure the vertical angle of arrival, or elevation angle, for more accurate geolocation of SuperDARN observations. However, the calibration of SuperDARN interferometer measurements remains challenging for several reasons, including a 2π phase ambiguity when solving for the time delay correction factor needed to account for differences in the electrical path lengths between signals received at the two antenna arrays. We present a new technique using multi‐frequency ionospheric and ground backscatter observations for the calibration of SuperDARN interferometer data, and demonstrate its application to both historical and recent data. Key Points: Calibration of Super Dual Auroral Radar Network (SuperDARN) interferometer angle of arrival data remains an outstanding challengeAnalysis of data at multiple frequencies can overcome the inherent 2π measurement ambiguity in the time delay correction factor (tdiff)Example applications are shown for historical and contemporary multi‐frequency SuperDARN observations [ABSTRACT FROM AUTHOR]

To obtain wide coverage and frequent wave observations, low-cost methods to observe significant wave heights and wave periods from moving vessels were developed by using Global Navigation Satellite System (GNSS) interferometric reflectometry. Because GNSS signals reflected from the sea surface are always delayed respect to those received directly from the satellite, and this delay depends on the distance between the antenna and the sea surface, the amplitude of the received GNSS signals, in which the direct and reflected signals are mixed, shows interferometric variations in the presence of ocean waves. High sampling rate observations of the GNSS signal amplitude can be used to determine the significant wave period and wave height by referring to a look-up table estimated from simulated received GNSS signals based on a realistic wave spectrum. The methods were applied to actual 20-Hz GNSS observations on a ferryboat and qualitatively good estimations of both significant wave heights and wave periods were obtained. Because the look-up tables can be further modified using in situ wave observations, these estimations can be quantitatively improved in the future. [ABSTRACT FROM AUTHOR]

NICE—Noise Interactive Catalogue Explorer—is a web service developed for rapid-qualitative glitch analysis in gravitational wave data. Glitches are transient noise events that can smother the gravitational wave signal in data recorded by gravitational wave interferometer detectors. NICE provides interactive graphical tools to support detector noise characterization activities, in particular, the analysis of glitches from past and current observing runs, passing from glitch population visualization to individual glitch characterization. The NICE back-end API consists of a multi-database structure that brings order to glitch metadata generated by external detector characterization tools so that such information can be easily requested by gravitational wave scientists. Another novelty introduced by NICE is the interactive front-end infrastructure focused on glitch instrumental and environmental origin investigation, which uses labels determined by their time–frequency morphology. The NICE domain is intended for integration with the Advanced Virgo, Advanced LIGO, and KAGRA characterization pipelines and it will interface with systematic classification activities related to the transient noise sources present in the Virgo detector. [ABSTRACT FROM AUTHOR]

In this research, a micromirror driven by electromagnetic force is designed and fabricated. The micromirror features a microfabricated L-shaped spring for large deflection and a bulk permanent magnet with a size of 1 × 1 × 1.5 mm3 mounted on the micromirror for generating electromagnetic actuation force. The device has a footprint of approximately 10 × 10 mm2. The design of the micromirror is based on Castigliano's theorem, theoretic spring constant evaluation, and finite element analysis, which are applied to estimate the deflection. The fabricated micromirror can be actuated at the resonance frequency in the atmosphere. The piston vibration at a fundamental frequency of 26.6 Hz is desirable for Michelson interferometers. An 830 µm stroke is achieved by applying 1 Vpp at the resonance frequency, and a 4.44° tilting angle is observed. Overall, the large stroke of the fabricated micromirror implies that the electromagnetic micromirror is promising for high-resolution interferometer applications. [ABSTRACT FROM AUTHOR]

This paper aims to present data recorded by a three-axial Fiber-Optic Rotational Seismograph (FORS). The laboratory and field tests showed a high correlation coefficient above 99% between two seismographs signals during the external disturbance, with an amplitude ranging from 0.5 mrad/s to 1.2 rad/s. This is achieved by ensuring a 100 ns time synchronization in the systems. At the same time, the Allan Variance analysis was applied to determine the basic parameters of random errors of the presented seismographs. The performed analysis indicates the angular random walk of 35–45 nrad/s/√Hz and a bias instability below 50 nrad/s. FORS offers the widest dynamic range available, at 170 dB, which is crucial during rotational seismology exploration due to its wide range of interest from seismology to engineering applications. Finally, a field research is also presented during an explosion in a closed limestone quarry in the border area.

NICE—Noise Interactive Catalogue Explorer—is a web service developed for rapid-qualitative glitch analysis in gravitational wave data. Glitches are transient noise events that can smother the gravitational wave signal in data recorded by gravitational wave interferometer detectors. NICE provides interactive graphical tools to support detector noise characterization activities, in particular, the analysis of glitches from past and current observing runs, passing from glitch population visualization to individual glitch characterization. The NICE back-end API consists of a multi-database structure that brings order to glitch metadata generated by external detector characterization tools so that such information can be easily requested by gravitational wave scientists. Another novelty introduced by NICE is the interactive front-end infrastructure focused on glitch instrumental and environmental origin investigation, which uses labels determined by their time–frequency morphology. The NICE domain is intended for integration with the Advanced Virgo, Advanced LIGO, and KAGRA characterization pipelines and it will interface with systematic classification activities related to the transient noise sources present in the Virgo detector.

A calibration system was designed to evaluate the accuracy of linear optical encoders at the micron level in a fast and economical manner. The system uses a commercial interferometer and motor stage as the calibrator and moving platform. Error analysis is necessary to prove the effectiveness and identify areas for optimization. A fixture was designed for the scale and interferometer target to meet the Abbe principle. A five-degree-of-freedom manual stage was utilized to adjust the reading head in optimal or suboptimal working conditions, such as working distance, offset, and angular misalignment. The results indicate that the calibration system has an accuracy of ±2.2 μm. The geometric errors of the calibration system, including mounting errors and non-ideal motions, are analyzed in detail. The system could be an inexpensive solution for encoder manufacturers and customers to calibrate a linear optical encoder or test its performance.

This paper proposes a dynamic phase comparison algorithm for planar direction finding on a high-speed moving satellite radio receiver, treating the moving antenna as equivalent to single-baseline array antennas. Based on a phase interferometer algorithm, this algorithm adjusts the baseline length according to the frequency measurement module and the satellite's high-speed motion to avoid phase ambiguity indirectly. By integrating the traditional amplitude comparison algorithm based on orthogonal dipole antennas, a dynamic fusion direction-finding method is proposed. Simulations demonstrate that this approach method not only covers a broader range of direction finding but also achieves higher accuracy, providing valuable insights for acquiring three-dimensional plasmagrams with space-borne plasma imagers. [ABSTRACT FROM AUTHOR]

Phase shift plays a vital role in the analysis of interference and manipulation of polarization behavior in interferometric techniques. The Sagnac interferometer (SI) is initially studied due to its ability to withstand external environmental factors, including noise, temperature, and other interferences. However, the real impact of these factors is not demonstrated. To address this, comparative studies are conducted involving both mathematical theories, simulations, and physical experiments of Sagnac and Mach-Zehnder interferometers (MZI), both utilizing a phase shift. The purpose is to explore the SI advantages over the MZI in a series of experiments with both interferometers to validate the superior configuration. Numerical simulations of the total electric field are performed at the output of these interferometers. By adjusting the orientation of a half-wave plate from 45 and 135 degrees at a step of 90 degrees, the interference fringe pattern and respective signal are generated. These simulation parameters are then implemented experimentally, and the results from both approaches are carefully analyzed and compared. It is shown that the light reflection through the SI setup makes it more tolerant to noise compared to the MZI. Consequently, these results confirm that the image intensity and pixel level of the SI are higher than that of the MZI, potentially leading to greater brightness for the simplified image analysis. [ABSTRACT FROM AUTHOR]

A calibration system was designed to evaluate the accuracy of linear optical encoders at the micron level in a fast and economical manner. The system uses a commercial interferometer and motor stage as the calibrator and moving platform. Error analysis is necessary to prove the effectiveness and identify areas for optimization. A fixture was designed for the scale and interferometer target to meet the Abbe principle. A five-degree-of-freedom manual stage was utilized to adjust the reading head in optimal or suboptimal working conditions, such as working distance, offset, and angular misalignment. The results indicate that the calibration system has an accuracy of ±2.2 μm. The geometric errors of the calibration system, including mounting errors and non-ideal motions, are analyzed in detail. The system could be an inexpensive solution for encoder manufacturers and customers to calibrate a linear optical encoder or test its performance. [ABSTRACT FROM AUTHOR]

Land subsidence, whether in its gradual down-settling form, creeping ground fracturing, or sudden sinkholes, is considered one of Iran's most catastrophic environmental challenges. The present study employed interferometric synthetic-aperture radar (InSAR) to detect land displacement in Garmsar City. The output maps reveal significant subsidence at 30 cm year−1 rates. According to the correlated subsidence map and piezometer data, groundwater harvesting for urban, industrial, and agricultural uses is primarily responsible for subsidence. High dependence on underground water resources and the absence of surface water resources in Iran's central regions have led to a radical decline in groundwater heads. For this target, 17 frames of images during 2015–2019 with a small temporal-perpendicular baseline were allocated and analyzed using the small baseline subset (SBAS). After removing unnecessary phases and noise, phase shift due to land deformation was extracted and converted to surface displacement. The InSAR analysis revealed a maximum of 37 cm and at least 33 cm subsidence for the Garmsar plain, and the average annual subsidence is estimated to be 36 cm, which is very close to the subsidence rate of the Tehran and Varamin plains. High-subsidence areas were generally located in the northern part of the Garmsar Plain, and subsidence rates decreased in the Southeast. The temporal and regional relationships between groundwater data and subsidence suggest that the general pattern of subsidence in the Garmsar Plain is caused by groundwater overexploitation, leading to widespread surface deformation. Since Garmsar is close to the capital, water resources are under pressure. By managing water resources in this area, this phenomenon will be reduced. [ABSTRACT FROM AUTHOR]

The possibility of increasing the resolution of X-ray phase-contrast imaging with a device based on a triple Laue-case interferometer is considered. To address one of the drawbacks of this scheme—the distortion of the interference pattern during diffraction of the object wave on the interferometer analyzer—it is proposed to replace the analyzer with two crystalline blocks of equal thickness. These blocks act as a diffraction lens, suppressing the mentioned distortions. Numerical simulations demonstrate that the low coherence of the initial radiation increases the quality of phase-contrast imaging using this method. [ABSTRACT FROM AUTHOR]

The digital correlator is one of the most crucial data processing components of a radio telescope array. With the scale of radio interferometeric array growing, many efforts have been devoted to developing a cost-effective and scalable correlator in the field of radio astronomy. In this paper, a 192-input digital correlator with six CASPER ROACH2 boards and seven GPU servers has been deployed as the digital signal processing system for Tianlai cylinder pathfinder located in Hongliuxia observatory. The correlator consists of 192 input signals (96 dual-polarization), 125-MHz bandwidth, and full-Stokes output. The correlator inherits the advantages of the CASPER system, for example, low cost, high performance, modular scalability, and a heterogeneous computing architecture. With a rapidly deployable ROACH2 digital sampling system, a commercially expandable 10 Gigabit switching network system, and a flexible upgradable GPU computing system, the correlator forms a low-cost and easily-upgradable system, poised to support scalable large-scale interferometeric array in the future.

The traditional method of joint calibration of fixed baseline interferometer with multiple errors requires more than three calibration emitters to achieve real-time calibration of the interferometer in orbit, but the performance of the traditional method will be reduced or even failed when the number of calibration emitters is insufficient. For the situation that the number of calibration emitters is insufficient, a single or double emitters calibration method for fixed baseline interferometer is proposed. Under the condition of relative motion between the interferometer and the calibration emitters, a set of phase differences of calibration signals is obtained firstly by multiple measurements, and a set of equations about the systematic errors of the interferometer is listed by using the obtained phase differences, finally the systematic errors are solved by the Penrose inverse matrix assisted iterative least squares method. The simulation results verify the feasibility of the proposed method. On this basis, the influence of the emitter selection on the positioning performance of the interferometer after calibration is analyzed qualitatively by means of numerical simulation, decomposing the parameters of the emitter selection. The analysis results show that the calibration emitter located near the sub-star in the single emitter case or two calibration emitters located far apart both can make the interferometer obtain better positioning performance after calibration.

Integrated photonic sensors have gained significant attention for biosensing applications. An especially potent design is the polarimetric waveguide interferometer, which utilizes polarization diversity for effective self-referencing. However, its implementations are held back by the need for bulky free-space optics or unreliable waveguide junctions for polarization handling. To overcome these limitations, we propose a novel concept for a compact photonic system that employs edge couplers to excite both polarizations from an optical fiber and an in-line polarizer to obtain the phase information in the fiber-based readout. Additionally, we improve the waveguide design methodology to minimize the limit of detection through balancing sensitivity with optical loss. To this end, we create a unified perturbative approach based on atomic force microscopy and ellipsometry data to model sensitivity, surface-roughness-induced scattering, absorption, and radiation. We then incorporate the coupling efficiency into a figure of merit for the combined system. Thus, we optimize the geometry of a strip waveguide on a CMOS-foundry-sourced silicon nitride platform for biosensing. Through exhaustive screening of the design space, we discover that polarization diversity simultaneously leverages high sensitivity and low overlap with sidewall roughness. Further, we present designs that eliminate the phase signal from two major noise sources: thermal and bulk refractive index fluctuations. Finally, we provide design recommendations and achieve a 5.2-fold improvement over a comparable bimodal waveguide interferometer. Thus, our aim is to design a robust, compact, sensitive, and cost-effective polarimetric waveguide interferometer through an efficient concept and an optimized design.

The Atacama Large Millimeter/submillimeter Array (ALMA) is a general purpose telescope that performs a broad program of astrophysical observations. Beginning in late 2016, solar observations with ALMA became available, thereby opening a new window onto solar physics. Since then, the number of solar observing capabilities has increased substantially but polarimetric observations, a community priority, have not been available. Weakly circularly polarized emission is expected from the chromosphere where magnetic fields are strong. Hence, maps of Stokes V provide critical new constraints on the longitudinal component of the chromospheric magnetic field. Between 2019 and 2022, an ALMA solar development effort dedicated to making solar polarimetry at millimeter wavelengths a reality was carried out. Here, we discuss the development effort to enable solar polarimetry in the 3 mm band (ALMA Band 3) in detail and present a number of results that emerge from the development program. These include tests that validate polarization calibration, including evaluation of instrumental polarization: both antenna-based "leakage" terms and off-axis effects (termed "beam squint" for Stokes V). We also present test polarimetric observations of a magnetized source on the Sun, the following sunspot in a solar active region, which shows a significant Stokes V signature in line with expectations. Finally, we provide some cautions and guidance to users contemplating the use of polarization observations with ALMA. [ABSTRACT FROM AUTHOR]

At the large-scale Krot facility (Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences), a new device was developed for laboratory simulations of the effects of the interaction of ultrawideband electromagnetic pulses with the partially ionized atmosphere and ionosphere: the "gigantic" coaxial line with a length of 10 m and diameter of 1.4 m that is filled by the decaying plasma of the inductive discharge. Two radiofrequency methods of wave diagnostics used in the device are described, the cutoff method and the wave interferometer, which can be used to determine the electron density of the plasma in the line in a wide range of values, Ne = 107–1011 cm–3. The measurement results are compared with the values obtained by the contact diagnostic, a probe with a microwave resonator. The interferometric method is implemented taking into account the nonuniform distribution of plasma density both along and across the transmission line, which, in the working range of pulsed and continuous diagnostic signals, is an oversized waveguide. The specific features of application and the limitations of the contact (probe) and contactless (wave) methods of diagnostics are discussed, taking into account the nonuniform plasma distribution in the coaxial line and the specific features of its construction. [ABSTRACT FROM AUTHOR]

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present the results on the impact of defocusing on the interference patterns obtained using three-block X-ray interferometers. Three types of defocused interferometers are constructed, manufactured, and tested: without a thick analyzer block, with a thick analyzer block, and with a separate thick block (magnifier). Fine structures in the interference patterns obtained from the three-block defocused interferometers are observed in cases where the interferometer analyzer block is thick or a magnifier (fourth thick block) is applied. Theoretical calculations show that the presence of defocusing, resulting from the overlap of beams on the input surface of the interferometer analyzer, forms an interference pattern in the form of parallel stripes (lines) lying in the scattering plane. The coordinates of the maxima of the interference fringes (lines) and the period of the fringes are calculated in cases with and without a thick crystal and the magnification factor. Experimental evidence shows that a thick crystal (magnifying crystal) does not introduce new information into the interference pattern but only increases its dimensions in the scattering plane. [ABSTRACT FROM AUTHOR]

Dynamic optical interferometric measurement method directly uses the liquid level as the reference surface, which immerses the tested object in liquid, and the interferograms are generated based on the optical path difference between the surfaces of the liquid and the object. The phase shift is realized by adjusting the incident angle of the laser with a rotation reflector. A generalized inhomogeneous phase shift algorithm is developed to suppress the micro-vibration of the liquid surface by the iterative least squares method combined with a confidence matrix. The high performance of the proposed method has been well verified in simulation and experiment. [ABSTRACT FROM AUTHOR]

Glyoxal (CHOCHO) is a trace gas in the atmosphere, often used as an indicator of biogenic emissions. It is frequently compared to formaldehyde concentrations, which serve as indicators of anthropogenic emissions, to gain insights into the characteristics of the environmental source. This study employed broadband cavity-enhanced absorption spectroscopy to detect gaseous CHOCHO, methylglyoxal, and NO2. Two different detection methods are compared. Spectrograph and CCD Detection: This approach involves coupling the system to a spectrograph with a charge-coupled device (CCD) detector. It achieved a 1 min 1-σ detection limit of 2.5 × 108 molecules/cm3, or 10 parts per trillion (ppt). Methylglyoxal and NO2 achieved 1 min 1-σ detection limits of 34 ppt and 22 ppt, respectively. Interferometer and PMT Detection: In this method, an interferometer is used in conjunction with a photomultiplier tube (PMT) detector. It resulted in a 2 min 1-σ detection limit of 1.5 × 1010 molecules/cm3, or 600 ppt. The NO2 2 min 1-σ detection limit was determined to be 900 ppt. Concentrations of methylglyoxal were difficult to determine using this method, as they appeared to be below the detection limit of the instrument. This study discusses the advantages and limitations of each of these detection methods. [ABSTRACT FROM AUTHOR]

Physical and mathematical numerical models have been developed to predict the effective acoustic properties of sound-absorbing honeycomb structures at sound pressure levels of 100 and 130 dB with normal sound wave incidence. The sound absorption coefficients and patterns of acoustic interactions of cells installed at the end of a cylindrical duct with normal sound wave incidence on them were studied by numerical mathematical and physical modeling. The sound absorption efficiency of single and groups of resonators of various shapes and sizes is estimated, and unique combinations of cells in groups are identified, taking into account their acoustic interactions. Representative samples of fragments of sound-absorbing structures were 3D-printed; laboratory tests of the samples were carried out with an interferometer with a normal sound wave incidence on the cells at a sound pressure level of 130 dB. [ABSTRACT FROM AUTHOR]

Three interferometers (the Sagnac sensor, the linear polarization interferometer, and the reflecting polarization interferometer) incorporated with the bow tie fiber are proposed to detect the seawater temperature. Bow tie fiber, a kind of polarization maintaining fiber, has stress induced birefringence. The three interferometers are categorized as transmission and reflection types to analyze the sensing principles. Related experiments are performed to explore the influence of the wavelength and length of the bow tie fiber on the sensitivity and free spectral range (FSR). The sensitivity and FSR both increase with the wavelength increasing. The sensitivity fluctuates in a small range and FSR decreases with the length increasing. The reflecting polarization interferometer has the bigger sensitivity of −1.19nm/°C than the other two. And it has the advantages of easy fabrication, simple operation, and good stability, so it is applicable in real ocean exploration. Our work can provide a reference to researchers who do oceanographic research. [ABSTRACT FROM AUTHOR]

Fiber-optic sensors, such as fiber Bragg grating (FBG) sensors and fiber-optic interferometers, have excellent sensing capabilities for industrial, chemical, and biomedical engineering applications. This paper used machine learning to enhance the number of fiber-optic sensing placement points and promote the cost-effectiveness and diversity of fiber-optic sensing applications. In this paper, the framework adopted is the FBG cascading an interferometer, and a deep belief network (DBN) is used to demodulate the wavelength of the sampled complex spectrum. As the capacity of the fiber-optic sensor arrangement is optimized, the peak spectra from FBGs undergoing strain or temperature changes may overlap. In addition, overlapping FBG spectra with interferometer spectra results in periodic modulation of the spectral intensity, making the spectral intensity variation more complex as a function of different strains or temperature levels. Therefore, it may not be possible to analyze the sensed results of FBGs with the naked eye, and it would be ideal to use machine learning to demodulate the sensed results of FBGs and the interferometer. Experimental results show that DBN can successfully interpret the wavelengths of individual FBG peaks, and peaks of the interferometer spectrum, from the overlapping spectrum of peak-overlapping FBGs and the interferometer.

Abstract Three interferometers (the Sagnac sensor, the linear polarization interferometer, and the reflecting polarization interferometer) incorporated with the bow tie fiber are proposed to detect the seawater temperature. Bow tie fiber, a kind of polarization maintaining fiber, has stress induced birefringence. The three interferometers are categorized as transmission and reflection types to analyze the sensing principles. Related experiments are performed to explore the influence of the wavelength and length of the bow tie fiber on the sensitivity and free spectral range (FSR). The sensitivity and FSR both increase with the wavelength increasing. The sensitivity fluctuates in a small range and FSR decreases with the length increasing. The reflecting polarization interferometer has the bigger sensitivity of −1.19nm/°C than the other two. And it has the advantages of easy fabrication, simple operation, and good stability, so it is applicable in real ocean exploration. Our work can provide a reference to researchers who do oceanographic research.

ABSTRACTAttosecond photoelectron spectroscopy has opened up for studying light–matter interaction on ultrafast time scales. It is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline based on a Mach-Zehnder interferometer. The active stabilization keeps the interferometer ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning range of [Formula: see text] fs. A tunable femtosecond laser source to drive high-order harmonic generation allows for precisely addressing atomic and molecular resonances. Furthermore, the interferometer includes a spectral shaper in 4f-geometry in the probe arm as well as a tunable bandpass filter in the pump arm, which offer additional high flexibility in terms of tunability as well as narrowband or polychromatic probe pulses. We demonstrate the capabilities of the beamline via experiments using several variants of the RABBIT (reconstruction of attosecond beating by two photon transitions) technique. In this setup, the temporal-spectral resolution of photoelectron spectroscopy can reach a new level of accuracy and precision.

The magnification effect provided by gravitational lensing overcomes the limitations of current observation instruments, allowing researchers to study faint objects at high redshift (z ≈ 4). Over the last decades, the sample of strong lenses has been mostly confined to optical bands. With the advent of (sub)millimeter wide field extragalactic surveys, about 200 strong lenses have been discovered in (sub)millimeter bands. Observations with high resolution and sensitivity from ALMA, NOEMA, and SMA, coupled with the flux boost from strong lensing, provide new windows to study galaxies at high redshift. Many works have investigated topics such as star formation, interstellar medium, and dynamic properties. The main objective of this paper is to review the current research status of galaxy-galaxy lensing in (sub)millimeter bands from the perspectives of observation samples, modeling methods, and scientific applications. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We propose a method for determining the collimation ratio of a coherent X-ray beam using a planar multilens interferometer. The method is based on the analysis of Talbot images, which are periodic patterns of interference fringes formed by the interferometer at corresponding distances. The high sensitivity of the position and period of the interference fringes to the shape of the X-ray beam wavefront enables determination of its collimation degree and evaluation of the coherence properties of the radiation. The effectiveness of the proposed approach is experimentally demonstrated at the ID15B beamline of the European Synchrotron Radiation Facility (ESRF) synchrotron radiation source. A theoretical study is carried out, and the corresponding results of computer simulation are presented. The experimental data obtained correspond fully to the theoretical estimates. [ABSTRACT FROM AUTHOR]

This paper reports an experimental system implemented to a Double Aperture Common Path Interferometer (DACPI) which automatically captures interferograms at the moment in which the system presents a minimum of mechanical vibrations. This is determined by m x n matrix analysis of a region of interest of the interferogram in question seeking to capture more stable images which will have an impact on an improvement for their subsequent analysis when the system does not have an optimum mechanical isolation. Experimental and comparative results with a non-optimized system are presented. [ABSTRACT FROM AUTHOR]

Abstract This article presents a direction‐finding method based on phase difference measurement for wide‐ranging applications of electronic intelligence. By including three processing steps of rotating, re‐scaling, and rounding of phase plane, the proposed method is able to obtain the actual phase shift of the longest baseline from the ambiguous phase differences measured from incoming signals with low computational cost. The method's performance is analysed and evaluated in terms of angle of arrival (AOA) estimation accuracy and probability of unambiguity by several interferometers of long baselines designed by multiple antenna elements. Consequently, an optimised array configuration of four antenna elements is taken into account to obtain high AOA estimation accuracy via several productive simulations and intensively validated with device measurement in the practical environment. Regarding the simulation of angle estimation accuracy, the proposed method remarkably outperforms two other existing methods, including second‐order difference array and correlative interferometers. In the experimental measurement, high AOA determination performance is achieved with the transmitter located around 35.5 m far from an antenna array and the small average angle estimation error of 1.86° at the direction of 20°. For various directions from −60° to 60° with the steps of 5°, the results satisfy the actual directions of the transmitter with a standard deviation of less than 0.5°.

Miniaturized, specific, rapid response and economical biosensors are finding applications in biotechnology, environmental studies, agriculture, food inspection and safety, disease diagnosis and medical utilities. Of the many categories of biosensors, optical biosensors have brought about an extra edge in sensing applications due to their selective, rapid and extremely sensitive measurements. Biosensors are analytical tools used to detect specific analytes such as cholesterol, urea, etc. having biomolecules such as nucleic acids, proteins, carbohydrates as key element for detecting these analytes along with a transducer and a data analysis and visualization tool. In case of optical biosensors the analyte is detected using light with either label based or label free techniques. In this paper some of the marked advances in the last decade in the field of optical biosensors have been reviewed with an emphasis on their fabrication approaches and growing application areas. Along with some of the carefully selected article on new developments in optical biosensors through the last decade, a brief historical review of optical biosensors since the breakthrough in optical biosensors in 1970s has also been presented. Another focus of the current review is the classification of biosensors, typical structures along with emerging developments in optical biosensing that are likely to impact the current decade. Major application areas and emerging applications through the last decade have been outlined to present a clear picture on the versatility of optical biosensors. Finally, the review also considers the challenges and future of emerging optical biosensing technologies in the current decade.

This paper proposes a dynamic phase comparison algorithm for planar direction finding on a high-speed moving satellite radio receiver, treating the moving antenna as equivalent to single-baseline array antennas. Based on a phase interferometer algorithm, this algorithm adjusts the baseline length according to the frequency measurement module and the satellite’s high-speed motion to avoid phase ambiguity indirectly. By integrating the traditional amplitude comparison algorithm based on orthogonal dipole antennas, a dynamic fusion direction-finding method is proposed. Simulations demonstrate that this approach method not only covers a broader range of direction finding but also achieves higher accuracy, providing valuable insights for acquiring three-dimensional plasmagrams with space-borne plasma imagers.

We describe the method for measuring the microwave current modulation amplitude of a diode laser with a vertical cavity. The method is based on comparison of the laser frequency shift upon a change in the constant current component and the shift induced by microwave modulation amplitude. This shift is due to the laser cavity heating. The knowledge of the current modulation amplitude is important for analysis of the laser modulation spectra with account for the dynamics of interaction of the spectral components with one another and with inversion. [ABSTRACT FROM AUTHOR]

In this work, a simulation study proposing a novel method for dual-sensing using surface plasmon resonance (SPR) optical fiber sensors and singlemode-multimode-singlemode (SMS) interferometer sensors was developed. The SPR theory was extended by integrating it with the MMI theory, enabling the simulation of an SPR–SMS sensor capable of sensing two parameters using a single channel. The proposed sensor structure consists of a tapered SMS with the multimode fiber cladding substituted by a gold layer for SPR excitation. The constructive parameters of the SMS structure were optimized, allowing the allocation of each effect's resonance dip to the desired range. The proposed sensor compensates for the cross-sensitivity between two parameters, enabling the sensing of temperature and RI using a single sensor channel. The resulting transmitted spectrum yielded two dips selected for sensing, with sensitivities of 2.680 µm/RIU and - 26.26 pm/K, with R 2 = 0.9937, for the SPR dip in the 540–620 nm range. For the SMS dip near 683 nm, the resulting sensitivities are 22.61 nm/RIU and 6.302 pm/K, with R 2 = 0.9983. [ABSTRACT FROM AUTHOR]

Organic crystals are poised to be a potential alternative to conventional silicon and its derivatives due to their utilization as microscale photonic components like active and passive waveguides, ring‐resonators, modulators, directional couplers, add‐on filters, interferometers (IMs), and reconfigurable circuits. Among these, IMs are important for flexible organic photonic integrated circuits. Here, the design and synthesis of extremely flexible (E)‐1‐(((5‐bromopyridin‐2‐yl)imino)methyl)naphthalen‐2‐ol (BPyIN) crystals are demonstrated. The interactions stabilizing the crystal packing and crystal‐substrate adhesion dictate the elasticity and pseudo‐plasticity, respectively. The extremely flexible BPyIN crystals disclose bending geometry‐dependent optical modes in the fluorescence spectra. This understanding is extended for fabricating a fiber loop mirror (FLM)‐like geometry using a BPyIN single crystal. Mechanophotonics approach facilitates the integration of FLM‐like crystal with a doubly bent waveguide to construct a first‐of‐its‐kind IM. The light propagating path‐length‐dependent optical interference within the IM is established. These proof‐of‐principle experiments illustrate the usefulness of mechanophotonics to fabricate miniature photonic devices beyond the traditional fabrication approach. [ABSTRACT FROM AUTHOR]

This paper proposes a method of using multiple spacecraft flying in formation in an artificially reduced halo orbit around the 2nd Lagrange point in the Sun–Earth system (SEL2) to make interferometric observations. One of the requirements for interferometric observations is to collect baseline vectors between telescopes or antennas. A shape-based approach is introduced to design a formation flight orbit that spirally spreads to satisfy this requirement. In this approach, orbits are designed on the basis of a linear theory. However, the formation orbits based on the linear theory quickly diverge because of the unstable dynamics around the SEL2. Therefore, the state-dependent Riccati equation, which allows for nonlinear control, is applied to orbit maintenance. The control system consists of two components: one for maintaining the reference orbit around the SEL2 and the other for controlling the relative position between the multiple spacecraft. The performance of the developed formation flight system is verified through a numerical simulation, confirming that the position accuracy requirement of the infrared interferometer is satisfied. It is also shown that both controls can be achieved with a low-thrust magnitude by using an electric propulsion system. • Formation flights around the Lagrange points are useful for interferometer. • An artificial halo orbit is designed with a reduced radius and a fixed shape. • Spacecraft formations are designed to collect more baseline vectors. • A nonlinear control is designed using the state-dependent Riccati equation. [ABSTRACT FROM AUTHOR]