Search

Accurate and stable measurement of inertial quantities is essential in geophysics, geodesy, fundamental physics, and inertial navigation. Here, we present an architecture for a compact cold-atom accelerometer-gyroscope based on a magnetically launched atom interferometer. Characterizing the launching technique, we demonstrate 700-parts per million gyroscope scale factor stability over 1 day, while acceleration and rotation rate bias stabilities of 7 × 10-7 meters per second squared and 4 × 10-7 radians per second are reached after 2 days of integration of the cold-atom sensor. Hybridizing it with a classical accelerometer and gyroscope, we correct their drift and bias to achieve respective 100-fold and 3-fold increase on the stability of the hybridized sensor compared to the classical ones. Compared to a state-of-the-art atomic gyroscope, the simplicity and scalability of our launching technique make this architecture easily extendable to a compact full six-axis inertial measurement unit, providing a pathway toward autonomous positioning and orientation using cold-atom sensors. [ABSTRACT FROM AUTHOR]

Temperature fluctuations induced by mountain waves can play a crucial role in the formation of polar stratospheric clouds (PSCs). In particular, the cold phase of the waves can lower local temperatures sufficiently to trigger PSC formation, even when large-scale background temperatures are too high. To provide new quantitative constraints on the relevance of this effect, this study analyzes a decade (2002–2012) of ice PSC detections obtained from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements and ERA5 data in the polar winter lower stratosphere. In the MIPAS observations, we find that approximately 52 % of the Arctic ice PSCs and 26 % of the Antarctic ice PSCs are detected at temperatures above the local Tice. Ice PSCs above Tice are concentrated around mountainous regions and their downwind directions. A backward-trajectory analysis is performed to investigate the temperature history of each ice PSC observation. The cumulative fraction of ice PSCs above Tice increases as the trajectory gets closer to the observation point. The most significant change in the fraction of ice PSCs above Tice occurs within the 6 h preceding the observations. At the observation point, the mean fractions of ice PSCs above Tice , taking into account temperature fluctuations along the backward trajectory, are 33 % in the Arctic and 9 % in the Antarctic. The results provide a quantitative assessment of the occurrence of ice PSCs above Tice in connection with orographic waves. Additionally, the observational statistics presented can be utilized for comparison with chemistry climate simulations. [ABSTRACT FROM AUTHOR]

We propose a new Fourier-transform spectroscopy technique based on the rotational Doppler effect. The technique offers an application for optical vortex frequency combs, where each frequency component carries a unique amount of orbital angular momentum (OAM). Here, we emulate a vortex comb using a tunable single frequency laser and a collection of spiral phase plates, generating up to 11 distinct OAM modes. Unlike in traditional Fourier-transform spectroscopy based on the Michelson interferometer (linear Doppler effect), the spectral resolution of vortex-comb spectroscopy is not limited by the mechanical scan distance of the instrument, but the instrument can be operated continuously without interruptions, leading to fast mode-resolved measurements. [ABSTRACT FROM AUTHOR]

In the past, satellite climatologies of gravity waves (GWs) have initiated progress in their representation in global models. However, these could not provide the phase speed and direction distributions needed for a better understanding of the interaction between GWs and the large-scale winds directly. The ESA Earth Explorer 11 candidate CAIRT could provide such observations. CAIRT would use a limb-imaging Michelson interferometer resolving a wide spectral range, allowing temperature and trace gas mixing ratio measurements. With the proposed instrument design, a vertical resolution of 1 km, along-track sampling of 50 km, and across-track sampling of 25 km in a 400 km wide swath will be achieved. In particular, this allows for the observation of three-dimensional (3D), GW-resolving temperature fields throughout the middle atmosphere. In this work, we present the methodology for the GW analysis of CAIRT observations using a limited-volume 3D sinusoidal fit (S3D) wave analysis technique. We assess the capability of CAIRT to provide high-quality GW fields by the generation of synthetic satellite observations from high-resolution model data and comparison of the synthetic observations to the original model fields. For the assessment, wavelength spectra, phase speed spectra, horizontal distributions, and zonal means of GW momentum flux (GWMF) are considered. The atmospheric events we use to exemplify the capabilities of CAIRT are the 2006 sudden stratospheric warming (SSW) event, the quasi-biennial oscillation (QBO) in the tropics, and the mesospheric preconditioning phase of the 2019 SSW event. Our findings indicate that CAIRT would provide highly reliable observations not only of global-scale GW distributions and drag patterns but also of specific wave events and their associated wave parameters. Even under worse-than-expected noise levels of the instrument, the resulting GW measurements are highly consistent with the original model data. Furthermore, we demonstrate that the estimated GW parameters can be used for ray tracing, which physically extends the horizontal coverage of the observations beyond the orbit tracks. [ABSTRACT FROM AUTHOR]

Raman spectroscopy allows for the unambiguous identification of materials through the inelastic scattering of light. This technique has a great many uses in various aspects of society from academic, scientific, and industry. This paper explores a specific type of Raman spectrometer called a spatial heterodyne Raman spectrometer (SHRSy), which is a variation of an interferometric spectrometer. It utilizes a Michelson interferometer and replaces the mirrors with gratings that transform it from a time-domain spectrometer to a spatial-domain spectrometer, allowing for the entirety of the spectrum to be captured at once. This study specifically tests a half-inch two-grating monolithic SHRS (½-in. 2g-mSHRS), which has a weight of <60 g and a size of 2.2 × 2.2 × 1.3 cm. To do this we excite a variety of organic liquids with a 532 nm neodymium-doped yttrium aluminum garnet (Nd:YAG) pulsed laser, using an excitation energy of 6.5 mJ/pulse and distance of 3 m in conjunction with an intensified charge-coupled device camera. This is the first time that the SHRS has been used for investigating polarized Raman spectra of liquids. We discuss and contrast the instrumental properties such as resolution, spectral range, étendue, and field of view with previously tested mSHRS to give context to the instrument's performance. [ABSTRACT FROM AUTHOR]

Previous research has consistently demonstrated that students often possess an inadequate understanding of fundamental quantum optics concepts, even after formal instruction. Findings from physics education research suggest that introducing a mathematical formalism to describe quantum optical phenomena may enhance students' conceptual understanding of quantum optics. This paper investigates whether using formal descriptions of quantum optics phenomena – such as photon anticorrelation at a beamsplitter or single-photon interference in a Michelson interferometer – expressed in Dirac notation, can support secondary school students in developing functional thinking about photons. To investigate this, we conducted a clusterrandomized field study, comparing the improvement in functional thinking between 67 students in the intervention group, who were taught using both qualitative and quantitative reasoning, and 66 students in the control group, who were taught using only qualitative reasoning. The results indicate that mathematical formalism can indeed promote functional thinking about photons. However, the comparison between the intervention and control groups revealed that the control group exhibited a greater increase in functional thinking than the intervention group. In response to these findings, we conducted a follow-up study aimed at gaining a deeper understanding of the cognitive load associated with both approaches. Specifically, we compared the intrinsic and extraneous cognitive load of 71 students in the intervention group with those of 65 students in the control group. The data analysis revealed that the two groups had statistically significant differences in intrinsic cognitive load while the extraneous cognitive load did not difer statistically significant, indicating a higher mental effort associated to the quantitative reasoning. [ABSTRACT FROM AUTHOR]

We studied the interaction between the neutral and charged excitons of monolayer MoSe2 at various temperatures via quantum beat spectroscopy in the time domain. We introduced temperature as an efficient control knob to regulate the relative photoluminescence intensities of the neutral and charged excitons to obtain maximum quantum beat resolution. Furthermore, our quantum beat measurements under different temperatures indicate that the decoherence time of the coupled exciton-trion state slightly decreases from 530 fs at 3.5 K to 420 fs at 63 K with increased temperature due to the low-energy acoustic phonon-induced dephasing. [ABSTRACT FROM AUTHOR]

This paper describes the design and principle of operation of a 20 m laser strainmeter of unequal-arm type created on the basis of a Michelson interferometer and frequency-stabilized helium–neon laser. The interferometry methods used allow the measurement of the displacement of an Earth's crust section on the base of the laser strainmeter with an accuracy of 30 pm in the frequency range from 0 (conventionally) to 1000 Hz. This laser strainmeter, when connected to an accurate time system providing an accuracy of 1 μs, should structurally become a part of the laser interferometric seismoacoustic observatory, consisting of spatially separated laser strainmeters installed in various regions of Russia. [ABSTRACT FROM AUTHOR]

This article examines the use of LEGO bricks as a tool for modeling physics phenomena in laboratory courses. The author provides examples of how LEGO bricks can be used to represent various concepts in physics, such as parabolic trajectories and oscillation graphs. The article also discusses the benefits of using LEGO bricks for inquiry-based learning and fostering students' comprehension and creativity in physics. While the author emphasizes the pedagogical value of LEGO bricks in physics education, they acknowledge the need for further research in this area. The article concludes by clarifying that it is not funded or sponsored by the LEGO company. [Extracted from the article]

In recent years, quantum Fourier transform infrared (QFTIR) spectroscopy has emerged as an alternative to conventional absorption spectroscopy in the mid-infrared region of the spectrum. By harnessing induced coherence and spectral correlations of photon pairs in a nonlinear Michelson interferometer, this technique offers promising potential for the practical detection of organic gases. However, little research was conducted to bring QFTIR spectrometers closer to domestic or in-field usage. In this work, we present the first use of a QFTIR spectrometer for open-path detection of multiple interfering organic gases in ambient air. We built a nonlinear Michelson interferometer with 1.7 m-long arms to increase the absorption length, coupled with analysis techniques from classical differential absorption spectroscopy used for gas-traces detection. We thus characterize our spectrometer's sensitivity to acetone, methanol, and ethanol vapors and demonstrate the accurate identification of mixtures of these gases released in ambient air. We show this characteristic is preserved over time by performing a measurement overnight and tracking the evolution of different gases' average concentrations. These results constitute the first use-case of a QFTIR spectrometer as a detector of organic gases and, thus, represent an important milestone toward the development of such detectors in practical situations. [ABSTRACT FROM AUTHOR]

Ocean salinity plays an important role in oceanographic research as one of the fundamental parameters. An optical salinometer based on the Michelson interferometer (MI) suitable for in situ measurement in deep-sea environments is proposed in this work, and it features real-time calibration and multichannel multiplexing using the frequency modulated continuous wave (FMCW) technique. The symmetrical sapphire structure used to withstand deep-sea pressure can not only achieve automatic temperature compensation, but also counteract the changes in optical path length under deep-sea pressure. A model formula suitable for optical salinity demodulation is proposed through the nonlinear least squares fitting method. In vertical profile testing, the optical salinometer demonstrated remarkable tracking performance, achieving an error of less than 0.001 psu. The sensor displays a stable salinity demodulation error within ±0.002 psu during a three-month long-term test at a depth of 4000 m. High stability and resolution make this optical salinometer have broad development prospects in ocean observation. [ABSTRACT FROM AUTHOR]

We studied the interaction between the neutral and charged excitons of monolayer MoSe2 at various temperatures via quantum beat spectroscopy in the time domain. We introduced temperature as an efficient control knob to regulate the relative photoluminescence intensities of the neutral and charged excitons to obtain maximum quantum beat resolution. Furthermore, our quantum beat measurements under different temperatures indicate that the decoherence time of the coupled exciton-trion state slightly decreases from 530 fs at 3.5 K to 420 fs at 63 K with increased temperature due to the low-energy acoustic phonon-induced dephasing. [ABSTRACT FROM AUTHOR]

Frequency encoded reconfigurable logic gates OR and AND are designed using interferometric switch based on quantum dot semiconductor optical amplifier (QDSOA) and simulated using MATLAB for the first time as far as our knowledge goes. The amplitude modulation (AM) and quality factor ( Q fe ) are calculated using numerical simulations confirming practical feasibility of the logic gates. This paper also investigates the effect of amplified spontaneous emission (ASE) noise on AM, Q fe and signal-to-noise ratio (SNR) values. AM below 0.005 dB and Q fe more than 30 dB ensure error free operation of the logic gates. [ABSTRACT FROM AUTHOR]

In this study, we present a novel method for measuring the magnetic susceptibility of liquids using a Mach–Zehnder interferometer. The proposed technique employs a ring magnet to deform the liquid, while a laser beam passes through the liquid to measure the resulting interference pattern. The deformation of the liquid, caused by the known magnetic field of the ring magnet, is used to calculate the magnetic susceptibility. We provide a comprehensive theoretical framework, including the relevant equations and models, for analyzing the data obtained using this method. We compare the Mach–Zehnder interferometer method with other established techniques, highlighting its advantages and disadvantages. Our findings indicate that the Mach–Zehnder interferometer technique offers high accuracy, sensitivity, and potential applications in characterizing the magnetic properties of various liquid systems. [ABSTRACT FROM AUTHOR]

Achieving rapid spectroscopic characterization is highly desirable for contactless, real‐time monitoring applications. However, it is challenging due to the trade‐off between short acquisition time and fine resolution. To address this challenge, a fully active scanning Fourier transform spectrometer (FTS) using thin‐film lithium niobate (TFLN) photonics is proposed. This work theoretically reveals relations between acquisition time and resolution and finds that their trade‐off can be notably alleviated by employing Michelson interferometer architectures. The proposed device consists of two broadband edge couplers and a tunable Michelson interferometer which includes 1.02 m‐length equivalent waveguides. The fabricated waveguides can achieve a wafer‐scale optical propagation loss of 12 ±$\pm$ 2.4 dB m−1${\rm m}^{-1}$, which enables the device to maintain a low insertion loss with a 1.02 m‐length equivalent waveguide. The proposed device can achieve an acquisition time of 10 μs$\umu{\rm s}$, a spectral resolution of 0.74 cm−1${\rm cm}^{-1}$ (i.e., 0.19 nm), and an operation wavelength range from 1260 to 1600 nm. [ABSTRACT FROM AUTHOR]

Electronic interferometers using the chiral, one-dimensional (1D) edge channels of the quantum Hall effect (QHE) can demonstrate a wealth of fundamental phenomena. The recent observation of phase jumps in a Fabry-Pérot (FP) interferometer revealed anyonic quasiparticle exchange statistics in the fractional QHE. When multiple integer edge channels are involved, FP interferometers have exhibited anomalous Aharonov-Bohm (AB) interference frequency doubling, suggesting putative pairing of electrons into 2 e quasiparticles. Here, we use a highly tunable graphene-based QHE FP interferometer to observe the connection between interference phase jumps and AB frequency doubling, unveiling how strong repulsive interaction between edge channels leads to the apparent pairing phenomena. By tuning electron density in-situ from filling factor ν < 2 to ν > 7 , we tune the interaction strength and observe periodic interference phase jumps leading to AB frequency doubling. Our observations demonstrate that the combination of repulsive interaction between the spin-split ν = 2 edge channels and charge quantization is sufficient to explain the frequency doubling, through a near-perfect charge screening between the localized and extended edge channels. Our results show that interferometers are sensitive probes of microscopic interactions and enable future experiments studying correlated electrons in 1D channels using density-tunable graphene. Previous measurements of interferometers based on quantum Hall (QH) edge channels have suggested potential electron pairing effects. Here, the authors investigate the coupling between QH edge channels in graphene Aharonov-Bohm (AB) interferometers, proposing a possible single-particle explanation for the apparent interference phase jumps and AB frequency doubling. [ABSTRACT FROM AUTHOR]

In this study, based on the OI135.6 nm night airglow data of the FY‐3D Ionospheric Photometer (IPM) during the 2018–2021 geomagnetically quiet period, the global wavenumber 4 longitudinal structure of the equatorial ionization anomaly (EIA) at 2:00 local time was discovered, and the component of the wavenumber 4 was extracted from these structures. Compared with the OI135.6 nm night airglow data of the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) F18 during 2011–2014, there were significant differences in the variation pattern of the relative amplitude of the two versus solar activity and the seasonal variation in the proportion of the component of the wavenumber 4. Based on the neutral wind speed observation results of the Michelson Interferometer for Global High‐Resolution Thermospheric Imaging on board the Ionospheric Connection Explorer (ICON) from 2020 to 2021, the longitudinal structures of the 4 ionospheric waves after midnight are related to the cross‐equatorial meridional wind. We believe that the wavenumber 4 longitudinal structures after midnight originate from the semidiurnal eastward‐propagating with zonal wavenumber 2 (SE2) nonmigrating tide in the cross‐equatorial neutral wind rather than the diurnal eastward‐propagating with zonal wavenumber 3 (DE3) nonmigrating tide in from the zonal wind, which modulates the daytime wavenumber 4 longitudinal structures. Plain Language Summary: The longitudinal structures of EIA have been extensively studied by using satellite data. However, there are few observations and studies, due to the weak ionosphere near midnight. In this paper, we studied the longitudinal structures of EIA at 02:00 local time during geomagnetically quiet period, benefitted from the satellite orbits and high sensitivity of FY‐3D IPM. We found that the wavenumber 4 longitudinal structures of EIA still exist at 02:00 local time and are obvious at equinoxes. Compared with SSUSI F18 data, FY‐3D IPM data showed different characteristics of wavenumber 4 component of EIA longitudinal structures. Because of the different local time of data between SSUSI F18 and FY‐3D IPM, we consider that the longitudinal wavenumber 4 structures of EIA after midnight originated from the cross‐equatorial neutral wind rather than the electric field modulated by zonal neutral wind in daytime. Key Points: The wavenumber 4 longitudinal structures of equatorial ionization anomaly (EIA) still exist after midnight and are more obvious at equinoxesThe wavenumber 4 component of EIA after midnight is positively correlated with the solar activity levelThe origin of the wavenumber 4 longitudinal structures of EIA after midnight is the modulation of the cross‐equatorial neutral wind [ABSTRACT FROM AUTHOR]

The paper proposes a method for detecting small oscillations in the length of interference fiber-optic sensors, which makes it possible to compensate for the problem of slow drift of the working point with a remote sensor. The result is achieved by combining homodyne demodulation methods with a tandem low-coherence interferometer. Theoretically and experimentally, the possibility of detecting acoustic effects in the operating frequency band of 4 kHz with a sensitivity of up to 0.3 nm has been shown. [ABSTRACT FROM AUTHOR]

This paper proposes a new order parameter model which satisfactorily explains complicated symmetry changes, the temperature–pressure (T–P) phase diagram and elastic anomalies observed experimentally with the improper ferroelastic phase transitions in multiferroic KMnF3 single crystal. First, it is shown that the order parameter model is transformed according to the four‐dimensional reducible representation of the wavevector star channel group. Second, based on the order parameter model and the singularity theory, the sixth‐order structurally stable Landau potential model is constructed. Finally, the theoretical T–P phase diagram is plotted and the elastic anomalies possible for each of the phase transitions are discussed. [ABSTRACT FROM AUTHOR]

Upper-atmosphere winds from a meteor radar and a field-widened Michelson interferometer, co-located at the Polar Environment Atmospheric Research Laboratory in Eureka, Nunavut, Canada (80° N, 86° W) are compared. The two instruments implement different wind-measuring techniques at similar heights and have very different temporal and spatial observational footprints. The meteor radar provides winds averaged over a ∼ 300 km horizontal area in 3 km vertical bins between 82 and 97 km on a 1 h cadence. The E-Region Wind Interferometer II (ERWIN) provides airglow-weighted winds (averaged over volumes of ∼ 8 km in height by ∼ 5 km radius) from three nightglow emissions (O(1S) , oxygen green line, 557.7 nm , 97 km ; an O2 line, 866 nm , 94 km ; and an OH line, 843 nm , 87 km) on a ∼ 5 min cadence. ERWIN's higher precision (1–2 ms-1 for the O(1S) and OH emissions and ∼ 4 ms-1 for the O2 emissions) and higher cadence allows more substantive comparisons between winds measured by meteor radar and Doppler shifts in airglow emissions than previously possible for similar meteor radar/airglow Doppler shift comparisons using Fabry–Perot interferometers. The best correlation is achieved using Gaussian weighting of meteor radar winds with peak height and vertical width being optimally determined. Peak heights agree well with co-located SABER airglow observations. Offsets between the two instruments are ∼ 1–2 ms-1 for the O2 and O(1S) emissions and less than 0.3 ms-1 for the OH emission. Wind directions are highly correlated with a ∼ 1:1 correspondence. On average, meteor radar wind magnitudes are ∼ 40 % larger than those from ERWIN. Gravity wave airglow brightness weighting of observations is discussed. Non-quadrature phase offsets between the airglow weighting and gravity wave associated wind and temperature perturbations will result in enhanced or reduced layer-weighted wind amplitudes. [ABSTRACT FROM AUTHOR]

The applications of ultrafast optics to biomedical microscopy have expanded rapidly in recent years, including interferometric techniques like optical coherence tomography and microscopy (OCT/OCM). The advances of ultra-high resolution OCT and the inclusion of OCT/OCM in multimodal systems combined with multiphoton microscopy have marked a transition from using pseudo-continuous broadband sources, such as superluminescent diodes, to ultrafast supercontinuum optical sources. We report anomalies in the dispersion profiles of low-coherence ultrafast pulses through long and non-identical arms of a Michelson interferometer that are well beyond group delay or third-order dispersions. This chromatic anomaly worsens the observed axial resolution and causes fringe artifacts in the reconstructed tomograms in OCT/OCM using traditional algorithms. We present DISpersion COmpensation Techniques for Evident Chromatic Anomalies (DISCOTECA) as a universal solution to address the problem of chromatic dispersion mismatch in interferometry, especially with ultrafast sources. First, we demonstrate the origin of these artifacts through the self-phase modulation of ultrafast pulses due to focusing elements in the beam path. Next, we present three solution paradigms for DISCOTECA: optical, optoelectronic, and computational, along with quantitative comparisons to traditional methods to highlight the improvements to the dynamic range and axial profile. We explain the piecewise reconstruction of the phase mismatch between the arms of the spectral-domain interferometer using a modified short-term Fourier transform algorithm inspired by spectroscopic OCT. Finally, we present a decision-making guide for evaluating the utility of DISCOTECA in interferometry and for the artifact-free reconstruction of OCT images using an ultrafast supercontinuum source for biomedical applications. [ABSTRACT FROM AUTHOR]

In the present article, we propose a monolithically integrated Michelson interferometer using a λ = 4 µm InGaAs/InAlAs quantum cascade laser as the light source. By using simple fringe detection and a four-point interpolation on each fringe, we will be able to detect minimal object displacements of 500 nm—corresponding to 25% of half the laser emission wavelength. Such an interferometric photonic integrated circuit has interesting applications for precision computerized numerical controlled machines. Since the industrial standard of such machines currently consists of glass-based linear encoders with a resolution of 5 µm, our interferometer-based system will enable an improvement of at least one order of magnitude. [ABSTRACT FROM AUTHOR]

The statistics of day‐to‐day tidal variability within 35‐day running mean windows is obtained from Michelson Interferometer for Global High‐Resolution Thermospheric Imaging (MIGHTI)/Ionospheric Connection Explorer (ICON) observations in the 90–107 km height region for the year 2020. Temperature standard deviations for 18 diurnal and semidiurnal tidal components, and for four quasi‐stationary planetary waves are presented, as function of latitude, altitude, and day‐of‐year. Our results show that the day‐to‐day variability (DTDV) can be as large as 70% of the monthly mean amplitudes, thus providing a significant source of variability for the ionospheric E‐region dynamo and hence for the F‐region plasma. We further validate our results with COSMIC‐2 ionospheric observations and present an approach to extend the MIGHTI/ICON results to all latitudes using Hough Mode Extension fitting, to produce global tidal fields and their statistical DTDV that are suitable as lower boundary conditions for nudging and ensemble modeling of TIE‐GCM. In the future, this will likely help to establish a data‐driven perspective of space weather variability caused by the tidal weather of the lower atmosphere. Key Points: Statistics of the day‐to‐day variability (DTDV) of diurnal and semidiurnal tides in the ionospheric dynamo region is obtained from Michelson Interferometer for Global High‐Resolution Thermospheric Imaging/Ionospheric Connection ExplorerDTDV is validated with COSMIC‐2 ionospheric observationsStatistics is extended to all latitudes using Hough Mode Extensions [ABSTRACT FROM AUTHOR]

We review recent research in various types of optical quantum computing using liquid crystal devices. First, we have investigated Young's Interference experiment using self-aligned liquid crystal (LC) devices and a logical "NOT" operation is achieved. Second, numerical quantization of interfering small photons using an LC retarder is investigated. Third, a Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) LC device was studied. Fourth, a basic experiment on 2-bit quantum calculations related to the Deutsch-Jozsa algorithm on a linear optical quantum computer using the LC device as a linear optical element was investigated. [ABSTRACT FROM AUTHOR]

In this article, we have presented a design of a quantum optomechanical gyroscope, consisting of a Michelson interferometer on a rotating table. An optical cavity with two moving mirrors is placed on one of the interferometer arms. Mirrors have freedom of movement in the x direction. Also, a sinusoidal movement in the y direction is applied to the entire optical cavity. The Coriolis force acting on the mirrors leads to a change in the optical path length of the cavity and then causes a change in the resonance frequency of it. This leads to an additional phase of radiation inside the cavity. We use the Heisenberg–Langevin equations of motion, to calculate the signal and noise of the output radiation of the interferometer, and then calculate the minimum rotation rate and its sensitivity that can be obtained from our gyroscope. It is shown that by using two moving mirrors, the sensitivity has been improved by more than 56 % compared with the cavity with one moving mirror. On the other hand, at temperatures of T = 0 K , T = 1 m K and T = 300 K , and by drawing the Allan deviation curve, Angular Random Walk noise and Bias Stability of the gyroscope were obtained. [ABSTRACT FROM AUTHOR]

Combined with vortex light and airglow, some different physical phenomena are presented in this paper. Based on the ground-based airglow imaging interferometer (GBAII) made by our group, a liquid crystal on silicon (LCoS) device on one arm of a wide-angle Michelson interferometer (MI) of the GBAII is replaced by the reflector mirror to become the GBAII-LCoS system. LCoS generates a vortex phase to convert a Gaussian profile airglow into a vortex light pattern. After the Gaussian profile vortex light equation is obtained by combining the Gaussian profile airglow with the Laguerre–Gauss light, three different physical phenomena are obtained: the simulated Gaussian vortex airglow beam exhibits a hollow phenomenon with the introduction of the vortex phase, and as the topological charge (TC) l increases, the hollow range also increases; after adding the vortex factor, the interference fringe intensity can be 'broadened' with the optical path difference (OPD) and TC l increases, which match the field broadening technology for solid wide-angle MI; the 'Four-point algorithm' wind measurement for the upper atmosphere based on the vortex airglow is derived, which is different from the usual expressions. Some experimental results are presented: We obtained the influence modes of vortex light interference and a polarization angle from 335° to 245°. We also obtained a series of interference images that verifies the rotation of the vortex light, onto which is loaded a set of superimposed vortex phase images with TC l = 3 into LCoS in turn, and the interference image is rotated under the condition of the polarization angle of 245°. The controlled vortex interference image for different TC and grayscale values are completed. [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]

The present study investigates wavenumber‐4 (wave‐4) structure in the longitude variation of zonal and meridional winds observed by the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument onboard the Ionospheric Connection Explorer (ICON) satellite. The amplitude of the wave‐4 pattern in meridional wind displays semi‐annual variation with equinoctial maxima whereas its seasonal variation in zonal wind shows maxima during August–October at the equatorial and low latitudes. The wave‐4 longitude variation maximizes at lower thermospheric heights (below 130 km) in zonal and meridional winds. It is considered primarily driven by the non‐migrating eastward propagating diurnal tide with zonal wavenumber‐3 (DE3) in the zonal wind. However, the amplitude of DE3 tide in the meridional wind does not show any enhancement during September–October. The seasonal variations of the wave‐4 amplitude and the DE3 tide are not similar in the zonal and meridional winds. The migrating ter‐diurnal tide (TW3) exhibits significant amplitudes during March–April and September–November in the meridional wind. In addition, the latitude variation of non‐migrating TE1 tide shows maximum amplitude during September–October. These results suggest that the non‐linear interaction between the TW3 and TE1 tides can serve as a potential source for the wave‐4 longitude variation in the meridional wind at lower thermospheric altitudes. Plain Language Summary: The four peaked longitudinal structure observed in ionosphere and thermosphere has long been investigated to determine its seasonal and inter‐annual variability in many parameters, as well as its sources, which can be of lower atmospheric origin. Earlier studies have shown that wave‐4 structure in the longitude variation of thermospheric zonal wind has large amplitudes between June and October. The investigation of ICON‐MIGHTI zonal wind confirms this. The wave‐4 pattern in the longitude variation of the meridional wind reveals that it has maxima during equinox different from the zonal wind. The DE3 tide is the primary contributor to the wave‐4 pattern in zonal wind. The DE3 shows large amplitudes during March–April however, it is weak during September–October in meridional wind. The source of wave‐4 pattern in the meridional wind is investigated. In meridional wind, the seasonal variation of migrating ter‐diurnal TW3 tide shows large amplitudes (40 m/s) during March–April and September–November. The non‐migrating ter‐diurnal TE1 tide shows enhanced amplitudes during September–October which suggests that the non‐linear interaction between the TW3 and TE1 tides can generate wave‐4 longitude structure in meridional wind at lower thermospheric altitudes. This study indicates the existence of other possible sources for the wave‐4 pattern observed in thermosphere. Key Points: Wave‐4 longitude structure in thermospheric meridional wind shows semi‐annual variation with equinoctial maxima at 100–110 kmThough DE3 tide does not show any enhancement during September–October, TW3 tide is found to be dominant in the meridional windIt is suggested that the non‐linear interaction between TW3 and TE1 tides can generate wave‐4 structure in thermospheric meridional wind [ABSTRACT FROM AUTHOR]

Electronic interferometries in integer and fractional quantum Hall regimes have unfolded the coherence, correlation, and statistical properties of interfering constituents. This is addressed by investigating the roles played by the Aharonov–Bohm effect and Coulomb interactions on the oscillations of transmission/reflection. Here, we construct magnetic interferometers using Cr-doped (Bi,Sb)2Te3 films and demonstrate the electronic interferometry using chiral edge states in the quantum anomalous Hall regime. By controlling the extent of edge coupling and the amount of threading magnetic flux, distinct interfering patterns were observed, which highlight the interplay between the Coulomb interactions and Aharonov–Bohm interference by edge states. The observed interference is likely to exhibit a long-range coherence and robustness against thermal smearing probably owing to the long-range magnetic order. Our interferometer establishes a platform for (quasi)particle interference and topological qubits. [ABSTRACT FROM AUTHOR]

Carbonyl sulfide (COS), a trace gas in our atmosphere that leads to the formation of aerosols in the stratosphere, is largely taken up by terrestrial ecosystems. Quantifying the biosphere uptake of COS could provide a useful quantity to estimate gross primary productivity (GPP). Some COS sources and sinks still contain large uncertainties, and several top-down estimates of the COS budget point to an underestimation of sources, especially in the tropics. We extended the inverse model TM5-4DVAR to assimilate Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite data, in addition to National Oceanic and Atmospheric Administration (NOAA) surface data as used in a previous study. To resolve possible discrepancies among the two observational data sets, a bias correction scheme is necessary and implemented. A set of inversions is presented that explores the influence of the different measurement streams and the settings of the prior fluxes. To evaluate the performance of the inverse system, the HIAPER Pole-to-Pole Observations (HIPPO) aircraft observations and NOAA airborne profiles are used. All inversions reduce the COS biosphere uptake from a prior value of 1053 GgS a -1 to much smaller values, depending on the inversion settings. These large adjustments of the biosphere uptake often turn parts of Amazonia into a COS source. Only inversions that exclusively use MIPAS observations, or strongly reduce the prior errors on the biosphere flux, maintain the Amazon as a COS sink. Inclusion of MIPAS data in the inversion leads to a better separation of land and ocean fluxes. Over the Amazon, these inversions reduce the biosphere uptake from roughly 300 to 100 GgS a -1 , indicating a strongly overestimated prior uptake in this region. Although a recent study also reported reduced COS uptake over the Amazon, we emphasise that a careful construction of prior fluxes and their associated errors remains important. For instance, an inversion that gives large freedom to adjust the anthropogenic and ocean fluxes of CS2 , an important COS precursor, also closes the budget satisfactorily with much smaller adjustments to the biosphere. We achieved better characterisation of biosphere prior and uncertainty, better characterisation of combined ocean and land fluxes, and better constraint of both by combining surface and satellite observations. We recommend more COS observations to characterise biosphere and ocean fluxes, especially over the data-poor tropics. [ABSTRACT FROM AUTHOR]

A novel two‐parameter sensor is proposed based on the abrupt taper and micro‐arc Michelson interferometer (MI) in single‐mode fiber. When there is a regular change in the liquid level or temperature, the phase difference changes, and the spectral intensity or wavelength of the interfering valleys of this sensor is directionally shifted. This study enriches the construction of MI and provides a new perspective on liquid level measurement. We experimentally explored the sensor's sensing performance over temperature and liquid level: this sensor's temperature sensitivity and liquid level sensitivity were up to 62.9 pm/°C and 0.2896 dB/mm, respectively. In addition, this sensor is characterized by compactness, simplicity, low cost, and high reliability, and it is suitable for measurement of liquid level and temperature, expanding the application field of MI. [ABSTRACT FROM AUTHOR]

We introduce a high-performance differential dilatometer based on an all-fiber Michelson interferometer at cryogenic temperature with 10−10 resolution in δL/L. It resolves the linear thermal expansion coefficient by measuring the oscillating changes of sample thickness and sample temperature with the interferometer and in situ thermometer, respectively. By measuring the linear thermal expansion coefficient α near the antiferromagnetic transition region of BaFe2As2 as a demonstration, we show that our dilatometer is able to measure thin samples with sub-pm-level length change resolution and mK-level temperature resolution. Despite the residual background thermal expansion of a few nm/K in the measurement results, our new dilatometer is still a powerful tool for the study of phase transition in condensed matter physics, especially has significant advantages in fragile materials with sub-100 μm thickness and being integrated with multiple synchronous measurements and tuning thanks to its extremely high resolution and contactless nature. The prototype design of this setup can be further improved in many aspects for specific applications. [ABSTRACT FROM AUTHOR]

Using the IMK–IAA data processor, methane and nitrous oxide distributions were retrieved from version-8 limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The dataset includes measurements from the nominal, upper troposphere–lower stratosphere, middle-atmosphere, upper-atmosphere and noctilucent-cloud observation modes. The processing differs from the previous version-5 data with respect to the atmospheric state variables that are jointly retrieved along with the target gases CH 4 and N 2 O, the treatment of the radiance offset, the selection of microwindows, the regularization, the spectroscopic data used and the treatment of horizontal variability of the atmospheric state. Besides the regular data product, a coarse-grid representation of the profiles with unity averaging kernels is available, as well as a specific research product for middle-atmosphere measurements resulting from a slightly different retrieval approach. The CH 4 errors are dominated by the large spectroscopic uncertainty for line intensities, which probably is too pessimistic, and estimated to be 21 %–34 % in the altitude range 6–68 km for northern midlatitude summer day conditions. The N 2 O errors are 7 %–17 % below 45 km. At higher altitudes they increase strongly due to nearly vanishing N 2 O amounts. Analysis of the horizontal averaging kernels reveals that for both gases the horizontal resolution is sampling-limited; i.e., information is not smeared over consecutive limb scans. Zonal-mean seasonal composites of both CH 4 and N 2 O exhibit the typical distribution of source gases with strong upwelling in the tropics and subsidence above the winter poles. Comparison with the previous data version shows several improvements: first, the vertical resolution of the retrieved CH 4 (N 2 O) profiles has generally been significantly enhanced and varies between 2.5 (2.5) and 4 (5) km at altitudes between 10 and 60 km, with the best resolution around 30 km for both species. Secondly, the number of non-converged retrievals has been clearly reduced, and thirdly, formerly strongly oscillating profiles are now considerably smoother. [ABSTRACT FROM AUTHOR]

Optical Bessel beams are used in numerous applications like fluorescence microscopy, material processing and optical trapping. These applications require Bessel beams having a central core with defined full width at half maximum and a defined axial length. Often, the side lobes of Bessel beams, which are associated with their non-diffracting properties, can interfere with the experimental process. We theoretically describe and practically verify the performance of a new refractive optical system to generate zoomable annular ring intensities. The ability to zoom the output ring diameter allows for flexibly choosing the Bessel beam parameters. Secondly, we introduce the use of a Michelson interferometer for destructively interfering Bessel beam side lobes in one direction. If two Bessel beams of zeroth order and first kind are coherently superposed with a small shift with respect to each other, their side lobes are enhanced in one direction and cancelled in the other direction. We suggest that applications like light-sheet microscopy can exploit the axis of destructive interference to improve their contrast. [ABSTRACT FROM AUTHOR]

The distinctive features of the T-15MD tokamak microwave interferometer for measuring linearly integrated electron density, as well as the system for processing and recording its signals, are presented. The phase stability of microwave interferometer signals is analyzed. The results of measurements with a microwave interferometer during the first experimental campaign of the T-15MD tokamak are presented. The phase values were extracted by using an analog phase meter and post-processing of digitized microwave interferometer signals: an intermediate frequency signal and a local oscillator signal. It is shown that the results of the plasma density calculation by these two methods coincide. [ABSTRACT FROM AUTHOR]

One of the most effective ways to advance the performance of quantum computers and quantum sensors is to increase the number of qubits or quantum resources in the system. A major technical challenge that must be solved to realize this goal for trapped-ion systems is scaling the delivery of optical signals to many individual ions. In this paper we demonstrate an approach employing waveguides and multi-mode interferometer splitters to optically address multiple 171Yb+ ions in a surface trap by delivering all wavelengths required for full qubit control. Measurements of hyperfine spectra and Rabi flopping were performed on the E2 clock transition, using integrated waveguides for delivering the light needed for Doppler cooling, state preparation, coherent operations, and detection. We describe the use of splitters to address multiple ions using a single optical input per wavelength and use them to demonstrate simultaneous Rabi flopping on two different transitions occurring at distinct trap sites. This work represents an important step towards the realization of scalable integrated photonics for atomic clocks and trapped-ion quantum information systems. A promising strategy for scaling trapped-ion-based quantum technologies is to use fully integrated optical waveguides to deliver light to numerous ions at multiple sites. Here, the authors. optically address three ions using on-chip waveguides to deliver three distinct wavelengths per ion, and perform Rabi flopping on each ion simultaneously. [ABSTRACT FROM AUTHOR]

A Michelson interferometer is commonly used for evaluating the morphology of a cell. However, the interference imaging with reference and object beams is easily affected by external vibrations and environmental disturbances, leading to unstable interference patterns. In this paper, the three-dimensional surface morphology of the biological cell is evaluated by a new quantitative phase imaging method, which couples Michelson-like lateral shear interferometric microscopy with self-referencing numerical phase calibration. The Michelson-like lateral shear interferometric microscopy is constructed by replacing the two plane mirrors of the traditional Michelson interferometer with two common right-angle prisms and generates interference fringe patterns. The lateral shear is created and freely adjustable by simply translating/or rotating one right-angle prism. To calculate the phase information of the biological cells quantitatively, the classical Fourier transform method is used to process the recorded interferogram, and then the self-referencing numerical phase calibration method is utilized for acquiring accurate phase information. Successfully achieving quantitative phase imaging of a cell verifies the feasibility and practicability of the proposed method. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet (VUV) light sensing shows great potential applications in the space science, materials, biophysics, and plasma physics. In this work, an all-optical detection method is proposed for VUV sensing by constructing an optical fiber-end Fabry-Pérot interferometer based on a single aluminum nitride (AlN) microwire. Compared with the traditional electrical devices, this all-optical detection method overcomes the difficulties like the fast response and electromagnetic interference immunity in detecting VUV bands at the present stage, and improves the response speed. The proposed device shows the excellent performance of VUV detection, with the static sensitivity of 1.03 nm/(W·cm−2), response rise time of down to 10 µs, and decay time of 0.64 ms. Beneficial from the excellent radiation resistance of AlN microwires and UV resistance of silica fibers, the proposed device is expected to have the good stability and potential applications in the fields of the solar physics and space exploration. [ABSTRACT FROM AUTHOR]

In future space-borne gravitational wave (GW) detectors, time delay interferometry (TDI) will be utilized to reduce the overwhelming noise, including the laser frequency noise and the clock noise etc., by time shifting and recombining the data streams in post-processing. The successful operation of TDI relies on absolute inter-satellite ranging with meter-level precision. In this work, we numerically and experimentally demonstrate a strategy for inter-satellite distance measurement. The distances can be coarsely determined using the technique of arm-locking ranging with a large non-ambiguity range, and subsequently TDI can be used for precise distance measurement (TDI ranging) by finding the minimum value of the power of the residual noises. The measurement principle is introduced. We carry out the numerical simulations, and the results show millimeter-level precision. Further, we perform the experimental verifications based on the fiber link, and the distances can be measured with better than 0.05 m uncertainty, which can well satisfy the requirement of time delay interferometry. [ABSTRACT FROM AUTHOR]

Optical interferometers are the main elements of interferometric sensing and measurement systems. Measuring their optical path difference (OPD) in real time and evaluating the measurement uncertainty are key to optimizing system noise and ensuring system consistency. With the continuous sinusoidal wavelength modulation of the laser, real-time OPD measurement of the main interferometer is achieved through phase comparison of the main and auxiliary interferometers. The measurement uncertainty of the main interferometer OPD is evaluated. It is the first evaluation of the impact of different auxiliary interferometer calibration methods on OPD measurements. A homodyne quadrature laser interferometer (HQLI) is used as the main interferometer, and a 3 × 3 interferometer is used as the auxiliary interferometer. The calibration of the auxiliary interferometer using optical spectrum analyzer scanning and ruler measurement is compared. The evaluation shows that the auxiliary interferometer is the most significant source of uncertainty and causes the total uncertainty to increase linearly with increasing OPD. It is proven that a high-precision calibration and large-OPD auxiliary interferometer can improve the real-time accuracy of OPD measurements based on the auxiliary interferometer. The scheme can determine the minimum uncertainty to optimize the system noise and consistency for vibration, hydroacoustic, and magnetic field measurements with OPDs of the ~m level. [ABSTRACT FROM AUTHOR]

A Michelson interferometer has been developed which uses a right-angled prism mirrored on the sides containing the right angle, to measure small tilt angles with double sensitivity compared to the classical Michelson interferometer. The design of the interferometer, theory, relative sensitivity as well as experimental results are presented. With this setup, we could measure tilt angle up to 1 μ rad . [ABSTRACT FROM AUTHOR]

The process whereby the supermassive black holes (SMBHs) populating the centers of galaxies have been assembled remains to be established, with the relative importance of seeds provided by collapsed Population III stars, black holes formed in nuclear star clusters via repeated mergers, or direct collapses of protogalactic disks yet to be determined. In this paper we study the prospects for casting light on this issue by future measurements of gravitational waves emitted during the inspirals and mergers of pairs of intermediate-mass black holes (IMBHs), discussing in particular the roles of prospective measurements by LISA and the proposed atom interferometers AION and AEDGE. We find that the expected number of detectable IMBH binaries is O (100) for LISA and AEDGE and O (10) for AION in low-mass seeds scenarios and goes down to O (10) for LISA and below one for AEDGE and AION in high-mass seed scenarios. This allows all of these observatories to probe the parameters of the seed model, in particular, if at least a fraction of the SMBHs arises from a low-mass seed population. We also show that the measurement accuracy of the binary parameters is, in general, best for AEDGE, which sees very precisely the merger of the binary. [ABSTRACT FROM AUTHOR]

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat provided infrared limb emission spectra, which were used to infer global distributions of CFC-11, CFC-12, and HCFC-22. Spectra were analysed using constrained non-linear least-squares fitting. Changes with respect to earlier data versions refer to the use of version 8 spectra, the altitude range where the background continuum is considered, details of the regularization and microwindow selection, and the occasional joint fitting of interfering species, the use of new spectroscopic data, the joint fit of a tangent-height-dependent spectral offset, and the use of 2D temperature fields. In the lower stratosphere the error budget is dominated by uncertainties in spectroscopic data, while above this measurement noise is the leading error source. The vertical resolution of CFC-11 and CFC-12 is 2–3 km near the tropopause, about 4 km at 30 km altitude, and 6–10 km at 50 km. The vertical resolution of HCFC-22 is somewhat coarser, 3–4 km at the tropopause and 10–12 km at 35 km altitude. In the altitude range of interest, the horizontal resolution is typically limited by the horizontal sampling of the measurements, not by the smearing of the retrievals. Horizontal information displacement does not exceed 150 km , which can become an issue only for comparisons with model simulations with high horizontal resolution or localized in situ observations. Along with the regular data product, an alternative representation of the data on a coarser vertical grid is offered. These data can be used without consideration of the averaging kernels. The new data version provides improvement with respect to reduction of biases and improved consistency between the full- and reduced-resolution mission period of MIPAS. [ABSTRACT FROM AUTHOR]

An architecture for a UV wind lidar dedicated to measuring vertical and lateral wind in front of an aircraft for gust load alleviation is presented. To optimize performance and robustness, it includes a fiber laser architecture and a Quadri Mach-Zehnder (QMZ) interferometer with a robust design to spectrally analyze the backscattered light. Different lidar parameters have been selected to minimize the standard deviation of wind speed measurement projected onto the laser axis, calculated through end-to-end simulations of the instrument. The optimization involves selecting an emission/reception telescope to maximize the amount of collected photons backscattered between 100 m and 300 m, a background filter to reduce noise from the scene, and photo-multiplier tubes (PMT) to minimize detection noise. Simulations were performed to evaluate lidar performance as a function of laser parameters. This study led to the selection of three laser architectures: a commercial solid-state laser, a design of a fiber laser, and a hybrid fiber laser resulting in standard deviations of 0.18 m/s, 0.17 m/s, and 0.09 m/s, respectively, at 10 km of altitude. To reconstruct the vertical and lateral wind on the flight path, the lidar is addressed to four different directions to measure four different projections of the wind. We calculate analytically (and validate through simulations) the addressing angle with respect to the flight direction that minimizes the root mean squared error (RMSE) between the reconstructed vertical and lateral wind components and the actual ones, assuming turbulence that follows the Von Karman turbulence model. We found that the optimum angle for an estimation at 100 m is about 50°, resulting in an improvement of about 50 % compared to an angle of 15°–20° typically used in current studies. [ABSTRACT FROM AUTHOR]

Small-scale temperature fluctuations can play a crucial role in the occurrence of ice clouds. This study analyzes a decade of ice polar stratospheric clouds (PSCs) occurrence obtained from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/Envisat) measurements. The points with the smallest temperature difference (Δ T ice_min) between the frost point temperature (T ice) and the environmental temperature along the limb line of sight are proposed here to identify the location of ice PSC observations. In MIPAS observations, we find approximately 56 % of the Arctic and 28 % of the Antarctic ice PSCs are detected at temperatures above the local T ice based on ERA5 data at Δ T ice_min. Ice PSCs above T ice are concentrated around mountain regions and their downwind directions. A backward trajectory analysis deduced from the ERA5 reanalysis is performed to investigate the temperature history of each ice PSC observation. Based on 24-hour backward trajectories, the cumulative fraction of ice PSCs above T ice increases as the trajectory gets closer to the observation point. The most significant change of the fraction of ice PSCs above T ice occurs within the 6h preceding the observations. There is an impact of previous temperature fluctuations on the interpretation of MIPAS ice PSC observations. At the observation point, the mean fractions of ice PSCs above T ice taking into account temperature fluctuations along the backward trajectory are 33 % in the Arctic and 9 % in the Antarctic. The results provide quantitative assessments of the correlation between orographic waves with ice PSCs above T ice based on the Lagrangian model by using MIPAS measurements and ERA5 reanalysis data. Additionally, the observational statistics presented can be utilized for comparison with chemistry-climate simulations. [ABSTRACT FROM AUTHOR]

A new type of Michelson interferometer (MI) based on a double hook structure is proposed for measurement of liquid level and temperature. The optical fiber MI based on the double‐hook structure is fabricated using a hydroxide flame heating device. Furthermore, the angle and sensing length of the double‐hook structure can be controlled by a rotating platform. The sensor is fixed on a ruler, which is set vertically on the iron support stand employing a beaker clamp, and the position of the beaker clamp is adjusted so that the double hook structure of the sensor overflows the water surface in the beaker. The temperature and liquid level sensitivities of the sensor are 129.8 pm/°C and −186.2 pm/mm, respectively. The novel optical fiber MI based on the double‐hook structure has the advantages of high sensitivity, low cost and easy fabrication, which has a great market prospect in production and life. [ABSTRACT FROM AUTHOR]

Suppose the velocity of light is independent of the source velocity. In that case, the reflection of light as a mechanical phenomenon predicts a zero fringe shift when applied to the Michelson interferometer with a particular geometry, a 0:40x10-4 fringe shift when applied to the Michelson interferometer presented in the Michelson–Morley experiment, and a 210 fringe shift when applied to the interferometer presented in this study, which contradicts the zero fringe shift experimental result. If the velocity of light depends on the source velocity, the reflection of light as a mechanical phenomenon predicts a zero fringe shift for all three experiments. The study of emission, propagation, and reflection of light as mechanical phenomena concludes that the optical phenomena are in an inertial frame as in the frame at absolute rest and cannot prove the motion of an inertial frame in which sources and mirrors belong to that inertial frame. [ABSTRACT FROM AUTHOR]

The detection of gas concentrations in harsh environments with high performance is an emerging research area. Ensuring that external factors do not affect the detection and that it is immune to electromagnetic interference are key factors in guaranteeing reliable gas detection in a variety of tough environments. Among all types of gas-sensing methods, photoacoustic (PA) methods based on optical interferometers offer high sensitivity, anti-electromagnetic interference capability, and non-magnetic saturation. This article first presents the basic principles and characteristics of the main optical interferometers, the PA effect, and the core technologies of PA gas-sensing methods. It then reviews advanced optical interferometer-based methods for PA gas sensing and summarizes their characteristics, including the heterodyne-based Mach-Zehnder interferometer (MZI), optical fiber-based MZI, Sagnac interferometer (SI)-based, diaphragm-based extrinsic Fabry-Perot (F-P) interferometer (EFPI), cantilever-based EFPI, cantilever-based Michelson interferometer (MI), difference-based MI, and membrane-less optical microphone–photoacoustic spectroscopy (MeoM–PAS) sensing methods. In particular, the MeoM–PAS methods for gas sensing are discussed in detail, as they offer a completely static measurement system and the separation of a PA gas cell from the measuring system for applications in complicated and adverse circumstances. This review also outlines the advantages and limitations of these PA gas-sensing technologies. [ABSTRACT FROM AUTHOR]

Space-based gravitational wave detection missions use multiple satellites to form a very large scale Michelson laser interferometer in space. This requires extremely high precision displacement measurements at the picometer level between test masses even millions of kilometers apart. Drag-free control is a key technology to ensure the ultra-static and ultra-stable space experiment platform for space-based gravitational wave detection. This paper proposes an innovative ground simulation scheme for drag-free control principle based on the Stewart platform. The kinematics and dynamics modeling of the Stewart platform used in the experiment is presented. A drag-free ground simulation experimental equipment is designed and built. A two-degree-of-freedom (2-DOF) drag-free controller is designed based on the H ∞ loop shaping algorithm which outperforms a PID controller in Simulink simulation. A semi-physical simulation experiment is conducted to verify the controller designed using rapid control prototyping technology. The experimental results show that the control performance reaches the limit accuracy of the hardware device, thus verifying the effectiveness of the drag-free control algorithm. • Introduce a novel ground simulation scheme for drag-free control using the Stewart platform. • Design a drag-free controller based on H ∞ loop shaping. • Validate our approach through a two-degree-of-freedom semi-physical simulation experiment. [ABSTRACT FROM AUTHOR]