- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Two-Branch Fiber Link for International Clock Networks
摘要： We present our work on realizing two-branch fiber links enabling multiple-partner clock comparisons in Europe. We report in detail on the setup connecting two long-haul links and report for the relative frequency stability and accuracy. We report on a combined uptime of 90% for our dual-branch link during almost 1 month. We finally discuss the combined uncertainty contribution of the ensemble of the link architecture to a clock comparison. We show that the frequency transfer uncertainty is 2 × 10^{-19}.
关键词： two-way noise compensation,phase measurement,ultrastable frequency transfer,Optical fiber links,phase lock loop
更新于2025-09-23 15:23:52
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Reconstruction of isolated moving objects with high 3D frame rate based on phase shifting profilometry
摘要： Recently, moving object reconstruction based on PSP has been attracted intensive research. The errors caused by the inner movement of PSP have been addressed successfully. However, when the object with discontinuities or isolated surface is measured and the temporal phase unwrapping method is applied, additional fringe patterns are required to unwrap the phase map. The object movement between the PSP fringe patterns and additional fringe patterns will cause unwrapping errors. This paper proposes a new method to reconstruct the moving object with discontinuous or isolated surface. The object movement is tracked and the influence on the phase map caused by the movement is analyzed. Then, the phase variation caused by the movement is obtained. The phase map of the object before movement is obtained by compensating the phase map of the object after movement based on the phase variations. Finally, the object is reconstructed by dual-frequency phase unwrapping method. A new projection strategy increasing the efficiency of the 3D frame rate is also presented in this paper. The 3D frame rate achieves half of the camera capture speed. The proposed method has high potential to be applied in industrial applications for real-time measurement of moving objects. Experiments are presented to verify the effectiveness.
关键词： Fringe analysis,Surface measurements,Phase shift.,Phase measurement
更新于2025-09-23 15:23:52
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Speckle-free common-path quantitative phase imaging with high temporal phase stability using a partially spatially coherent multi-spectral light source
摘要： Quantitative phase imaging (QPI) has been an important technique for the determination of various biophysical parameters, such as the refractive index and morphology of biological cells and tissues. The technique has been implemented using off-axis and common path digital holographic microscopy (DHM). Off-axis DHM, though being ideal for QPI, offers lower temporal phase stability compared to common path techniques. Common path DHM offers a higher temporal phase stability but, being a coherent imaging technique, suffers from speckle artefacts and spurious interference fringes due to the high coherence of the light source. Both artefacts not only degrade the image quality, but also affect the phase measurement results. In this paper, we report the implementation of common path QPI set-up using a partially spatially coherent multi-spectral light source. The spatial coherence of the red and green color lasers is reduced by using a rotating diffuser. Also, a speckle free QPI was implemented using common path Fresnel biprism interferometer. A Fresnel biprism is used in the self-referencing mode, thus offering the advantage of no optical power loss in addition to high temporal stability and the least speckle artefacts. Furthermore, it is very easy to implement, as the system completely replaces the need for spatial filtering at the source end as well as for the reference beam generation. The experiments have been carried out on industrial and biological samples to prove the effect.
关键词： phase measurement,Fresnel biprism interferometer,digital holography,coherence
更新于2025-09-23 15:23:52
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Phase aberration compensation for digital holographic microscopy based on double fitting and background segmentation
摘要： We propose a purely automatic and accurate phase aberration compensation method in digital holographic microscopy for phase-contrast imaging of living cells. At first, a least-squares fitting procedure is implemented to correct a large proportion of the phase aberrations. Subsequently, the flat phase background is retrieved based on phase gradient and image segmentation. Finally, the residual phase aberrations are eliminated in another least-squares fitting procedure performed within the background region. This method needs no manual intervention or prior knowledge of optical setup. Not only phase curvature but also high order aberrations could be corrected without extra components. It outperforms the phase-variation-minimization method in terms of noise robustness and calculation speed. The performance of the proposed method is demonstrated with simulated and experimental results.
关键词： Phase measurement,Digital holographic microscopy,Aberration compensation
更新于2025-09-23 15:22:29
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Experimental optical phase measurement approaching the exact Heisenberg limit
摘要： The use of quantum resources can provide measurement precision beyond the shot-noise limit (SNL). The task of ab initio optical phase measurement—the estimation of a completely unknown phase—has been experimentally demonstrated with precision beyond the SNL, and even scaling like the ultimate bound, the Heisenberg limit (HL), but with an overhead factor. However, existing approaches have not been able—even in principle—to achieve the best possible precision, saturating the HL exactly. Here we demonstrate a scheme to achieve true HL phase measurement, using a combination of three techniques: entanglement, multiple samplings of the phase shift, and adaptive measurement. Our experimental demonstration of the scheme uses two photonic qubits, one double passed, so that, for a successful coincidence detection, the number of photon-passes is N = 3. We achieve a precision that is within 4% of the HL. This scheme can be extended to higher N and other physical systems.
关键词： Heisenberg limit,adaptive measurement,entanglement,quantum metrology,optical phase measurement
更新于2025-09-23 15:21:01
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Removing Random Phase Contributions of Sweeping Local Oscillator From Modulated RF Measurements
摘要： This paper proposes a measurement strategy to remove the random phase contributions of the sweeping local oscillator (LO) from modulated radio frequency phase measurements based on downconversion. To obtain a stable phase spectrum for each run of tone-by-tone sweeping measurement, the LO used for downconversion is coupled out to an extra path and modulated to be a wideband multisine signal. By monitoring the phase change of multisine signal at a specific and fixed frequency point, random LO phase offsets during the frequency sweep can be measured and compensated. In this paper, two experimental test benches with the same core measurement strategy but different architectures are established for method validation. According to the experimental results using test bench one, the phase stability is ±(0.2°–0.4°) at 1.8 GHz for fundamental mixing-based downconversion and ±(0.6°–1°) for harmonic mixing at 6 GHz. Based on test bench two, relative phase deviations of ±(0.8°–1.2°) at 22 GHz for fundamental mixing and ±(2°–3°) at 66 GHz for harmonic mixing are reachable.
关键词： modulated measurement,Local oscillator (LO),phase measurement,mixer,vector network analyzer (VNA)
更新于2025-09-23 15:21:01
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Measuring plasmonic phase using radiallypolarized confocal surface plasmon interferometer
摘要： Conventional surface plasmon interferometry allows microscopic sensing of materials using the so-called V(z) curve, which actually refers to module of complex V(z) effect while the phase information is lost. This work proposes a simple and compact configuration to measure the plasmonic phase of tested materials within the localized focal spot region of radially polarized light using curve. A home-developed experimental configuration is applied, involving the basic concepts of virtual confocal annulus and embedded phase-shifting configuration. A modified model of confocal surface plasmon interferometry is established to explain why an attenuated beam profile is strictly required in the phase measurement. And procedures on how to achieve beam profile attenuation and phase-shifting simultaneously using a single phase-sensitive spatial light modulator (SLM) is elaborated. Experimental verification is demonstrated as well.
关键词： Radial polarization,Phase-shifting,Surface plasmon microscopy,Common-path interferometer,Phase measurement
更新于2025-09-19 17:13:59
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Detecting the Extremely Small Angle of an Axicon by Phase-Shifting Digital Holography
摘要： Axicon is an optical element that can be used to produce high-quality Bessel beams efficiently. In general, the smaller the base angle of the axicon is, the longer the diffraction-free distance of the generated Bessel beam will be. Therefore, axicon with an extremely small base angle is important for the generation of Bessel beam. However, the measurement of an extremely small base angle is a challenge. Here, we applied the phase-shifting digital holography in the measurement of axicon angle. The errors of the three measured axicons with base angles of 0.5°, 1°, and 1° were 1.94%, 4.43%, and 1.63%, respectively.
关键词： digital holography,axicon,phase measurement,phase shift
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Coherent Beam Combining of 37 Femtosecond Fiber Amplifiers
摘要： For the last few years, coherent beam combining (CBC) has been drastically increasing the performances of ytterbium-doped femtosecond fiber amplifiers, up to more than 10 mJ output energy and to the multi-kilowatt level [1,2]. CBC consists in coherently adding the output beams of several independent amplifiers seeded by a common source. This method involves both an efficient combination process along with a phase detection and control technique applied on all the beams to combine. However, for femtosecond pulses to reach the Joule level and address applications such as particles acceleration, several thousands of fibers need to be combined. Thus, highly scalable CBC architectures along with adapted phase measurements techniques need to be investigated. The XCAN project, a collaboration between Ecole Polytechnique and Thales, aims at demonstrating such a highly scalable CBC system in the femtosecond regime, involving 61 fibers as a target point. It consists in a tiled-aperture configuration where the fibers are stacked in a hexagonal array and collimated by a hexagonal microlens array. Besides, an interferometric phase measurement technique is implemented, which allows to determine the phase shifts of all the beams in one single frame acquired from a fast camera and to correct them with a kHz bandwidth feedback loop. This detection method has been demonstrated to be theoretically scalable up to about 10,000 fibers [3]. First proof of principles of the XCAN project have been published with 19 passive fibers and 7 high power fiber amplifiers [4,5]. In this paper, we report on the CBC of 37 fiber amplifiers in the femtosecond regime in the way towards our goal of 61 channels.
关键词： XCAN project,interferometric phase measurement,femtosecond fiber amplifiers,coherent beam combining
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Josephson Arbitrary Waveform Synthesizer as a Reference Standard for the Measurement of the Phase of Harmonics in Distorted Signals
摘要： We use the Josephson arbitrary waveform synthesizer to provide traceability for the phase of the harmonics, relative to its fundamental, of a distorted waveform. For distorted waveforms with rms values in the range from 0.154 V to 0.2 V and harmonic magnitudes from 5% to 40 % of the fundamental, our system can generate odd harmonics up to the 39th with phase uncertainties from 0.002° to 0.010° (k=2.0), depending on the harmonic number and harmonic magnitude.
关键词： Josephson junction array,measurement techniques,measurement quantum voltage standards,standards,phase measurement,spectrum analysis
更新于2025-09-10 09:29:36