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Showing papers on "Interferometry published in 2020"


Journal ArticleDOI
TL;DR: A new era in which strict coherence and interferometry are no longer prerequisites for quantitative phase imaging and diffraction tomography is highlighted, paving the way toward new generation label-free three-dimensional microscopy, with applications in all branches of biomedicine.

243 citations


Reference BookDOI
24 Jul 2020
TL;DR: In this paper, the effect of irradiation on the optical properties of fibers has been investigated using interference microscopes and back-scattering of light waves from fibers, and automatic analysis of interferograms.
Abstract: An introduction to fiber structure Principles of interferometry Two-beam interferometry applied to fibrous materials Multiple-beam interferometry applied to fibrous materials Interferometric determination of fiber surface topography The effect of irradiation on the optical properties of fibers Interference microscopes Back-scattering of light waves from fibers Automatic analysis of interferograms References Author index Subject index

157 citations


Journal ArticleDOI
TL;DR: A novel control scheme is developed for this frequency-dependent squeezed vacuum source and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as "A+."
Abstract: The first detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015 launched the era of gravitational-wave astronomy. The quest for gravitational-wave signals from objects that are fainter or farther away impels technological advances to realize ever more sensitive detectors. Since 2019, one advanced technique, the injection of squeezed states of light, is being used to improve the shot-noise limit to the sensitivity of the Advanced LIGO detectors, at frequencies above ∼50 Hz. Below this frequency, quantum backaction, in the form of radiation pressure induced motion of the mirrors, degrades the sensitivity. To simultaneously reduce shot noise at high frequencies and quantum radiation pressure noise at low frequencies requires a quantum noise filter cavity with low optical losses to rotate the squeezed quadrature as a function of frequency. We report on the observation of frequency-dependent squeezed quadrature rotation with rotation frequency of 30 Hz, using a 16-m-long filter cavity. A novel control scheme is developed for this frequency-dependent squeezed vacuum source, and the results presented here demonstrate that a low-loss filter cavity can achieve the squeezed quadrature rotation necessary for the next planned upgrade to Advanced LIGO, known as "A+."

92 citations


Journal ArticleDOI
TL;DR: This article presents a methodology to increase the estimation accuracy of DS interferometry, with emphasis on spatiotemporal coherence refinement, and integrates this method into SqueeSAR technique and simultaneously take the advantage of StaMPS into consideration.
Abstract: The state-of-the-art techniques have demonstrated that coherence error degrades the performance of synthetic aperture radar (SAR) interferometry (InSAR) for distributed scatterers (DSs). This article aims at fully evaluating the influence of coherence error on DS InSAR time-series analysis. In particular, we present a methodology to increase the estimation accuracy of DS interferometry, with emphasis on spatiotemporal coherence refinement. The motive behind this is that bias removal and variance mitigation of sample coherence matrix impose optimum weighting for estimating phase series and geophysical parameters of interest, whereas maximization of temporal coherence in a reference network can avoid spatial error propagation during the least-squares adjustment. Rather than developing independent processing chains, we integrate this method into SqueeSAR technique and simultaneously take the advantage of StaMPS into consideration. Using simulation and real data over southwestern China, comprehensive comparisons before and after spatiotemporal coherence refinement are performed over various coherence scenarios. The results tested from different phase and displacement rate estimators validate the effectiveness of the presented method.

87 citations


Journal ArticleDOI
TL;DR: The Zhaoshan long-baseline Atom Interferometer Gravitation Antenna (ZAIGA) is a new type of underground laser-linked interferometer facility, and is currently under construction.
Abstract: The Zhaoshan long-baseline Atom Interferometer Gravitation Antenna (ZAIGA) is a new type of underground laser-linked interferometer facility, and is currently under construction. It is in the 200-m...

86 citations


Journal ArticleDOI
TL;DR: An ultrasensitive refractive index (RI) sensor based on enhanced Vernier effect is proposed, which consists of two cascaded fiber core-offset pairs that functions as a Mach-Zehnder interferometer (MZI) and a low-finesse Fabry-Perot interferometers (FPI).
Abstract: An ultrasensitive refractive index (RI) sensor based on enhanced Vernier effect is proposed, which consists of two cascaded fiber core-offset pairs. One pair functions as a Mach-Zehnder interferometer (MZI), the other with larger core offset as a low-finesse Fabry-Perot interferometer (FPI). In traditional Vernier-effect based sensors, an interferometer insensitive to environment change is used as sensing reference. Here in the proposed sensor, interference fringes of the MZI and the FPI shift to opposite directions as ambient RI varies, and to the same direction as surrounding temperature changes. Thus, the envelope of superimposed fringe manifests enhanced Vernier effect for RI sensing while reduced Vernier effect for temperature change. As a result, an ultra-high RI sensitivity of -87261.06 nm/RIU is obtained near the RI of 1.33 with good linearity, while the temperature sensitivity is as low as 204.7 pm/ °C. The proposed structure is robust and of low cost. Furthermore, the proposed scheme of enhanced Vernier effect provides a new perspective and idea in other sensing field.

86 citations


Journal ArticleDOI
TL;DR: In this article, the authors extend the concept of dynamical decoupling from spin to mechanical degrees of freedom of macroscopic objects, for application in interferometry, and present the case of levitated (or free falling) nanodiamonds hosting a color center in a magnetic field gradient.
Abstract: We extend the concept of dynamical decoupling from spin to mechanical degrees of freedom of macroscopic objects, for application in interferometry. In this manner, the superposition of matter waves can be made resilient to many important sources of noise when these are driven along suitable paths in space. As a concrete implementation, we present the case of levitated (or free falling) nanodiamonds hosting a color center in a magnetic field gradient. We point out that these interferometers are inherently affected by diamagnetic forces, which restrict the separation of the superposed states to distances that scale with the inverse of the magnetic field gradient. Periodic forcing of the mechanical degree of freedom is shown to overcome this limitation, achieving a linear-in-time growth of the separation distance independent of the magnetic field gradient, while simultaneously protecting the coherence of the superposition from environmental perturbations.

76 citations


Journal ArticleDOI
10 Aug 2020
TL;DR: In this paper, a new type of quantum interferometer was recently realized that employs parametric amplifiers (PAs) as the wave splitting and mixing elements, which produced quantum entangled fields for probing the phase change signal in the interferometers.
Abstract: A new type of quantum interferometer was recently realized that employs parametric amplifiers (PAs) as the wave splitting and mixing elements. The quantum behavior stems from the PAs, which produce quantum entangled fields for probing the phase change signal in the interferometer. This type of quantum entangled interferometer exhibits some unique properties that are different from traditional beam splitter-based interferometers such as Mach–Zehnder interferometers. Because of these properties, it is superior to the traditional interferometers in many aspects, especially in the phase measurement sensitivity. We will review its unique properties and applications in quantum metrology and sensing, quantum information, and quantum state engineering.

62 citations


Journal ArticleDOI
TL;DR: A full-loop Stern-Gerlach atom interferometer is realized, opening perspectives to examine the quantum nature of gravity and a new era of fundamental probes, including the realization of previously inaccessible tests at the interface of quantum mechanics and gravity.
Abstract: The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furthermore, several theoretical studies have explained why such an interferometer is a formidable challenge. Here we provide a detailed account of the first full-loop Stern-Gerlach interferometer realization, based on highly accurate magnetic fields, originating from an atom chip, that ensure coherent operation within strict constraints described by previous theoretical analyses. Achieving this high level of control over magnetic gradients is expected to facilitate technological as well as fundamental applications, such as probing the interface of quantum mechanics and gravity. While the experimental realization described here is for a single atom, future challenges would benefit from utilizing macroscopic objects doped with a single spin. Specifically, we show that such an experiment is in principle feasible, opening the door to a new era of fundamental probes.

60 citations


Journal ArticleDOI
TL;DR: In this paper, an improved multipoint interferometer (IMI) was proposed for measuring the orbital angular momentum (OAM) of an optical vortex with high topological charge, which can be used for measuring OAM of light from astronomical sources.
Abstract: A multipoint interferometer (MI), uniformly distributed point-like pinholes in a circle, was proposed to measure the orbital angular momentum (OAM) of vortex beams [Phys. Rev. Lett.101, 100801 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.100801], which can be used for measuring OAM of light from astronomical sources. This is a simple and robust method; however, it is noted that this method is only available for low topological charge because the diffracted intensity patterns for vortex beams with higher OAM will repeat periodically. Here, we propose an improved multipoint interferometer (IMI) for measuring the OAM of an optical vortex with high topological charge. The structure of our IMI is almost the same as the MI, but the size of each pinhole is larger than a point in the MI. Such a small change enables each pinhole to get more phase information from the incident beams; accordingly, the IMI can distinguish any vortex beams with different OAM. We demonstrate its viability both theoretically and experimentally.

60 citations


Journal ArticleDOI
20 Jun 2020
TL;DR: In this article, the authors demonstrate an f-2f interferometer through second-harmonic generation and subsequent supercontinuum generation in a single dispersion-engineered waveguide with a stabilization performance equivalent to a conventional off-chip module.
Abstract: The measurement and stabilization of the carrier–envelope offset frequency fCEO via self-referencing is paramount for optical frequency comb generation, which has revolutionized precision frequency metrology, spectroscopy, and optical clocks. Over the past decade, the development of chip-scale platforms has enabled compact integrated waveguides for supercontinuum generation. However, there is a critical need for an on-chip self-referencing system that is adaptive to different pump wavelengths, requires low pulse energy, and does not require complicated processing. Here, we demonstrate efficient fCEO stabilization of a modelocked laser with only 107 pJ of pulse energy via self-referencing in an integrated lithium niobate waveguide. We realize an f-2f interferometer through second-harmonic generation and subsequent supercontinuum generation in a single dispersion-engineered waveguide with a stabilization performance equivalent to a conventional off-chip module. The fCEO beatnote is measured over a pump wavelength range of 70 nm. We theoretically investigate our system using a single nonlinear envelope equation with contributions from both second- and third-order nonlinearities. Our modeling reveals rich ultrabroadband nonlinear dynamics and confirms that the initial second-harmonic generation followed by supercontinuum generation with the remaining pump is responsible for the generation of a strong fCEO signal as compared to a traditional f-2f interferometer. Our technology provides a highly simplified system that is robust, low in cost, and adaptable for precision metrology for use outside a research laboratory.

Journal ArticleDOI
TL;DR: A Sagnac interferometer suitable for rotation sensing is described, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap, and achieves a rotation sensitivity comparable to Earth's rate in about 10 min of operation.
Abstract: We describe a Sagnac interferometer suitable for rotation sensing, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap. The atom wave packets are split and recombined by standing-wave Bragg lasers, and the trapping potential steers the packets along circular trajectories with a radius of 0.2 mm. Two conjugate interferometers are implemented simultaneously to provide common-mode rejection of noise and to isolate the rotation signal. With interference visibilities of about 50%, we achieve a rotation sensitivity comparable to Earth's rate in about 10 min of operation. Gyroscope operation was demonstrated by rotating the optical table on which the experiment was performed.

Journal ArticleDOI
20 Dec 2020
TL;DR: In this article, the authors implemented a mid-IR frequency-domain OCT based on ultra-broadband entangled photon pairs spanning from 3.3 to 4.3 µm, and demonstrated 10 µm axial and 20 µm lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples.
Abstract: Mid-infrared (mid-IR) light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons, making mid-IR sources and detectors obsolete. Here we implement mid-IR frequency-domain OCT based on ultra-broadband entangled photon pairs spanning from 3.3 to 4.3 µm. We demonstrate 10 µm axial and 20 µm lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples. By intrinsically being limited only by shot noise, we observe 106 times more sensitivity per integration time and power of the probe light. Together with the vastly reduced footprint and technical complexity, our technique can outperform conventional approaches with classical mid-IR light sources.

Journal ArticleDOI
TL;DR: Insight is provided into the phenomenon of superresolution through incoherent imaging that has attracted much attention recently and will find a wide range of applications over a broad spectrum of frequencies, from fluorescence microscope to stellar interferometry.
Abstract: We solve the general problem of determining, through imaging, the three-dimensional positions of N weak incoherent pointlike emitters in an arbitrary spatial configuration. We show that a structured measurement strategy in which a passive linear interferometer feeds into an array of photodetectors is always optimal for this estimation problem, in the sense that it saturates the quantum Cramer-Rao bound. We provide a method for the explicit construction of the optimal interferometer. Further explicit results for the quantum Fisher information and the optimal interferometer design that attains it are obtained for the special case of one and two incoherent emitters in the paraxial regime. This work provides insights into the phenomenon of superresolution through incoherent imaging that has attracted much attention recently. Our results will find a wide range of applications over a broad spectrum of frequencies, from fluorescence microscopy to stellar interferometry.

Journal ArticleDOI
TL;DR: An all-optical method to directly reconstruct the band structure of semiconductors based on the temporal Young's interferometer realized by high harmonic generation with a few-cycle laser pulse, paving the way to study matters under ambient conditions and to track the ultrafast modification of band structures.
Abstract: We propose an all-optical method to directly reconstruct the band structure of semiconductors. Our scheme is based on the temporal Young's interferometer realized by high harmonic generation with a few-cycle laser pulse. As a time-energy domain interferometer, temporal interference encodes the band structure into the fringe in the energy domain. The relation between the band structure and the emitted harmonic frequencies is established. This enables us to retrieve the band structure from the spectrum of high harmonic generation with a single-shot measurement. Our scheme paves the way to study matters under ambient conditions and to track the ultrafast modification of band structures.

Journal ArticleDOI
TL;DR: In this paper, a new type of quantum entangled interferometer was recently realized that employs parametric amplifiers as the wave splitting and recombination elements, which produced quantum correlated fields for probing the phase change signal in the interferometers.
Abstract: A new type of quantum entangled interferometer was recently realized that employs parametric amplifiers as the wave splitting and recombination elements. The quantum entanglement stems from the parametric amplifiers, which produce quantum correlated fields for probing the phase change signal in the interferometer. This type of quantum entangled interferometer exhibits some unique properties that are different from traditional beam splitter-based interferometers such as Mach-Zehnder interferometers. Because of these properties, it is superior to the traditional interferometers in many aspects, especially in the phase measurement sensitivity. We will review its unique properties and applications in quantum metrology and sensing, quantum information, and quantum state engineering.

Journal ArticleDOI
TL;DR: In vivo cellular-resolution imaging of human skin is demonstrated in both B-scan and C-scan modes, with the possibility to navigate within the skin tissues in real time.
Abstract: Line-field confocal optical coherence tomography (LC-OCT) is a recently introduced technique for ultrahigh-resolution vertical section (B-scan) imaging of human skin in vivo. This work presents a new implementation of the LC-OCT technique to obtain horizontal section images (C-scans) in addition to B-scans. C-scan imaging is achieved with this dual-mode LC-OCT system using a mirror galvanometer for lateral scanning along with a piezoelectric chip for modulation of the interferometric signal. A quasi-identical spatial resolution of ∼ 1 µm is measured for both B-scans and C-scans. The images are acquired in both modes at a rate of 10 frames per second. The horizontal field of view of the C-scans is 1.2 × 0.5 mm2, identical to the vertical field of view of the B-scans. The user can switch between the two modes by clicking a button. In vivo cellular-resolution imaging of human skin is demonstrated in both B-scan and C-scan modes, with the possibility to navigate within the skin tissues in real time.

Journal ArticleDOI
TL;DR: In this paper, a review of interferometer arrangements and processing techniques for volatile organic compounds (VOCs) detection is presented, including the basis of each technique, applications and limitations, and the prospects to realize a miniaturized, high sensitive and multiplex interferometric sensors based on the recent technology are suggested.
Abstract: Exposure to volatile organic compounds (VOCs) is widely associated with adverse health effects. Detection and monitoring of VOCs are important for maintaining safe and healthy industrial and domestic environments. Interferometry is a highly-sensitive optical measurement technique that has been widely applied to a vast range of physical parameters from the speed of light to temperature and has also been used to detect VOCs at the sub-ppm range. Owing to the vast range of interferometer arrangements and processing techniques, this review assesses the different approaches adopted in detecting VOCs. Different interferometry arrangements including the Fabry-Perot interferometry, Sagnac interferometry and Mach-Zehnder interferometry are reviewed for VOC detection, including the different sensing films and materials employed. We present the basis of each technique, applications and limitations. The different interferometry techniques are summarized by comparing the sensitivity, limit of detection, linearity, response time and the challenges of current interferometry techniques. Lastly, prospects to realize a miniaturized, high-sensitive and multiplex interferometric sensors based on the recent technology are suggested.

Journal ArticleDOI
TL;DR: In this article, an in-fiber Mach-Zehnder Interferometer (MZI) based on hollow core fiber (HCF) was fabricated and experimentally demonstrated.
Abstract: An in-fiber Mach–Zehnder Interferometer (MZI), based on hollow core fiber (HCF), for measuring curvature is fabricated and experimentally demonstrated. The sensing part was fabricated by splicing a section of HCF between two sections of multimode fiber (MMF), and different HCF lengths were investigated in order to achieve the highest curvature sensitivity. These devices were tested in a transmission configuration using lead-in and lead-out single mode fibers (SMF). The sensor was attached to a steel sheet by using the polymer Polydimethylsiloxane (PDMS) for accurate control of the applied curvature. The modal analysis was carried out using a commercial software based on finite element method (FEM) and by incorporating some of the experimental data, it was feasible to determine the two dominant modes that interfere in this sensor. The devices were characterized by measuring the fringe contrast variations due to the curvature changes. The interferometer fabricated with a HCF 2.5 mm in length HCF showed the highest curvature sensitivity, −17.28 ± 2.30 dB/m−1, in a range from 1.84 m−1 to 2.94 m−1. Moreover, the sensor that exhibited a better performance was fabricated with a HCF length of 1 mm, combining the most extensive curvature range (from 0.95 m−1 to 2.68 m−1) and an adequate sensitivity (−11.80 ±1.30 dB/m−1). The analysis of the interferometric signal of this device in Fourier domain, allows us to establish a one to one relationship between the contrast and the curvature in a broader range (from 0 m−1 to 2.94 m−1). Moreover, the fringe contrast showed a very low dependency on temperature (from 30 °C to 90 °C), depicting that this device was not affected by temperate fluctuation.


Journal ArticleDOI
TL;DR: In this article, an ultra-high sensitive photonic crystal fiber (PCF) salinity sensor based on the sagnac interferometer (SI) was proposed for measurement of salinity in seawater.
Abstract: For a sensor, high sensitivity, structural simplicity, and longevity are highly desired for measurement of salinity in seawater. This work proposed an ultrahigh sensitive photonic crystal fiber (PCF) salinity sensor based on the sagnac interferometer (SI). The propagation characteristics of the proposed PCF are analyzed by the finite element method (FEM). The achieved sensitivity reaches up to 37,500 nm/RIU and 7.5 nm/% in the salinity range from 0% to 100%. The maximum resolutions of 2.66 × 10−06 RIU and 1.33 × 10−02% are achieved with high linearity of 0.9924 for 2.20 cm length of the proposed PCF. Owing to such excellent results, this proposed sensor offers the potential to measure the salinity of seawater.

Journal ArticleDOI
Fang Wang1, Kaibo Pang1, Tao Ma1, Xu Wang1, Yufang Liu1 
TL;DR: In this paper, a folded-tapered multimode-no-core (FTMN) fiber structure with an additional Mach-Zehnder interferometer (MZI) was proposed and experimentally demonstrated.
Abstract: In this paper, a refractive index (RI) and temperature sensor based on a folded-tapered multimode-no-core (FTMN) fiber structure is proposed and experimentally demonstrated. The FTMN has an additional Mach-Zehnder interferometer (MZI), which is introduced in the folded-tapered multimode (FTM) fiber. And with the inherent multimode interference (MMI) and the previously mentioned MZI as foundation, a composite interference is successfully established. This synthetic composite interference greatly improves the performance of traditional optical fiber RI sensing in the low RI range. The experimental results demonstrate that a maximum sensitivity of 1191.5 nm/RIU within a linear RI ranging from 1.3405 to 1.3497 can be achieved, which is greater than the traditional modal interferometer structure. Furthermore, the temperature sensitivities at interference dips A and B are 0.0648 nm/°C and 0.0598 nm/°C, respectively. By monitoring the wavelength shifts of interference dips A and B, the sensor can simultaneously measure RI and temperature to overcome the temperature induced cross-sensitivity.

Journal ArticleDOI
TL;DR: This work proposes and theoretically demonstrate an integrated polarization beam splitter on the x-cut lithium-niobate-on-insulator (LNOI) platform based on a Mach-Zehnder interferometer with an anisotropy-engineered multi-section phase shifter.
Abstract: We propose and theoretically demonstrate an integrated polarization beam splitter on the x-cut lithium-niobate-on-insulator (LNOI) platform. The device is based on a Mach-Zehnder interferometer with an anisotropy-engineered multi-section phase shifter. The phase shift can be simultaneously controlled for the TE and TM polarizations by engineering the length and direction of the anisotropic LNOI waveguide. For TE polarization, the phase shift is −π/2, while for TM polarization, the phase shift is π/2. Thus, the incident TE and TM modes can be coupled into different output ports. The simulation results show an ultra-high polarization extinction ratio of ∼47.7 dB, a low excess loss of ∼0.9 dB and an ultra-broad working bandwidth of ∼200 nm. To the best of our knowledge, the proposed structure is the first integrated polarization beam splitter on the x-cut LNOI platform.

Journal ArticleDOI
TL;DR: In this paper, a nonlinear interferometer using non-degenerate spontaneous parametric down-conversion (SPDC) with a Fourier-transform spectroscopy concept is presented for registration of spectral information.
Abstract: Nonlinear interferometers allow spectroscopy in the mid-infrared range by detecting correlated visible light, for which non-cooled detectors with higher specific detectivity and lower dark count rates are available. We present a new approach for the registration of spectral information, which combines a nonlinear interferometer using non-degenerate spontaneous parametric down-conversion (SPDC) with a Fourier-transform spectroscopy concept. In order to increase the spectral coverage, we use broadband non-collinear SPDC in periodically poled LiNbO3. Without the need for spectrally selective detection, continuous spectra with a spectral bandwidth of more than 100 cm−1 are achieved. We demonstrate transmission spectra of a polypropylene sample measured with 6 cm−1 resolution in the spectral range between 3.2 µm to 3.9 µm.

Journal ArticleDOI
TL;DR: In this paper, a high-sensitive Mach-Zehnder interferometric temperature fiber-optic sensor based on core-offset splicing technique by filling the interferometer with refractive index matching liquid was demonstrated.

Journal ArticleDOI
TL;DR: In this paper, a new analysis offers a way to derive relatively simple analytical limits on quantum measurements even for complex or poorly understood systems, with applications in imaging, interferometry, and quantum-information processing.
Abstract: A new analysis offers a way to derive relatively simple analytical limits on quantum measurements even for complex or poorly understood systems, with applications in imaging, interferometry, and quantum-information processing.

Journal ArticleDOI
TL;DR: A Nomarski polarizing prism has been used in conjunction with a focused laser differential interferometer to measure the phase velocity of a density disturbance at sampling frequencies ≥10MHz.
Abstract: A Nomarski polarizing prism has been used in conjunction with a focused laser differential interferometer to measure the phase velocity of a density disturbance at sampling frequencies ≥10MHz. Use of this prism enables the simultaneous measurement of density disturbances at two closely spaced points that can be arbitrarily oriented about the instrument’s optical axis. The orientation is prescribed by rotating the prism about this axis. Since all four beams (one beam pair at each measurement point) propagate parallel to one another within the test volume, any bias imparted by density fluctuations away from the measurement plane on the disturbance phase velocity is minimized. A laboratory measurement of a spark-generated shock wave and a wind tunnel measurement of a second-mode instability wave on a cone model in a Mach 6 flow are presented to demonstrate the performance of the instrument. High-speed schlieren imaging is used in both cases to verify the results obtained with the instrument.

Journal ArticleDOI
TL;DR: The first practical application of nonlinear interferometry is demonstrated by measuring the displacement of an atomic force microscope microcantilever with quantum noise reduction of up to 3 dB below the standard quantum limit, corresponding to a quantum-enhanced measurement of beam displacement of 1.7 fm/sqrt[Hz].
Abstract: Nonlinear interferometers that replace beam splitters in Mach-Zehnder interferometers with nonlinear amplifiers for quantum-enhanced phase measurements have drawn increasing interest in recent years, but practical quantum sensors based on nonlinear interferometry remain an outstanding challenge. Here, we demonstrate the first practical application of nonlinear interferometry by measuring the displacement of an atomic force microscope microcantilever with quantum noise reduction of up to 3 dB below the standard quantum limit, corresponding to a quantum-enhanced measurement of beam displacement of $1.7\text{ }\text{ }\mathrm{fm}/\sqrt{\mathrm{Hz}}$. Further, we minimize photon backaction noise while taking advantage of quantum noise reduction by transducing the cantilever displacement signal with a weak squeezed state while using dual homodyne detection with a higher power local oscillator. This approach may enable quantum-enhanced broadband, high-speed scanning probe microscopy.

Journal ArticleDOI
TL;DR: The proposed Michelson interferometric fiber-optic acoustic sensor based on a large-area gold diaphragm exhibits superiorities of compact size, high sensitivity, flat low-frequency response and ease of mass production, which gives the sensor great potential for low- frequencies acoustic sensing and photo-acoustic spectroscopy.
Abstract: A Michelson interferometric fiber-optic acoustic sensor based on a large-area gold diaphragm is proposed in this paper. The Michelson interferometer (MI) based on 3×3 coupler is comprised of two beams that reflected from the gold diaphragm and a cleaved fiber end face. Thickness and diameter of the gold diaphragm are 300 nm and 2.5 mm, respectively. Based on the phase difference between each output port of the 3×3 fiber coupler, an ellipse fitting differential cross multiplication (EF-DCM) interrogation process is induced for phase demodulation, which can overcome the phase distortion caused by property degradation of 3×3 coupler. Experimental results show that the sensor has a phase sensitivity of about -130.6 dB re 1 rad/μPa@100 Hz. A flat response range between 0.8 to 250 Hz is realized with the sensitivity fluctuation below 0.7 dB. Besides, the signal-to-noise ratio (SNR) and minimal detectable pressure (MDP) of the sensor are 57.9 dB and 10.2 mPa/Hz1/2 at 5 Hz. The proposed sensor exhibits superiorities of compact size, high sensitivity, flat low-frequency response and ease of mass production, which gives the sensor great potential for low-frequency acoustic sensing and photo-acoustic spectroscopy.

Journal ArticleDOI
TL;DR: The ground-based differential interferometry synthetic aperture radar (GBD-DInSAR) is a promising deformation measurement technology developed in the last 20 years as discussed by the authors, which is capable of sensing millimeter-scale deformations in the range of tens of meters to several kilometers from the target area in a continuous, all-weather environment.
Abstract: Ground-based differential interferometry synthetic aperture radar (GB-DInSAR) is a promising deformation measurement technology developed in the last 20 years. The GBDInSAR system is capable of sensing millimeter-scale deformations in the range of tens of meters to several kilometers from the target area in a continuous, all-weather environment. This article introduces in detail the basic principles of GB-DInSAR imaging, conventional signal models, deformationinversion algorithms, system working mode, existing typical systems, and application examples of high-precision deformation measurement in different scenarios. Moreover, this article systematically summarizes the latest research progress of GB-DInSAR technology and its future direction of development.