High Coherence Research Articles

Topological Charge Measurement of a Partially Coherent Vortex Beam Using Dual Cylindrical Lenses with an Arbitrary Angle

For a partially coherent Laguerre–Gaussian (PCLG) vortex beam, information regarding the topological charge (TC) is concealed in the cross-spectral density (CSD) function phase. Herein, a flexible method for the simultaneous determination of the sign and magnitude of the TC for a PCLG vortex beam is proposed based on the measured CSD amplitude and phase after the beam propagates through a dual cylindrical lens with adjustable angles. Both the stripes in the CSD amplitude and phase exhibit quantitative relationships with the value of TC, that is, N=2l+1. Meanwhile, the angle adjustability of cylindrical lenses allows flexible measurements, thus rendering the scheme effective for both high and extreme coherences.

Eddy and tidal driven basal melting of the Totten and Moscow University ice shelves

The mass loss from the neighboring Totten and Moscow University ice shelves is accelerating and may raise global sea levels in coming centuries. Totten Glacier is mostly based on bedrock below sea level, and so is vulnerable to warm water intrusion reducing its ice shelf buttressing. The mechanisms driving the ocean forced sub-ice-shelf melting remains to be further explored. In this study, we simulate oceanic-driven ice shelf melting of the Totten (TIS) and Moscow University ice shelves (MUIS) using a high spatiotemporal resolution model that resolves both eddy and tidal processes. We selected the year 2014 as representative of the period 1992 to 2017 to investigate how basal melting varies on spatial and temporal scales. We apply the wavelet coherence method to investigate the interactions between the two ice shelves in time-frequency space and hence estimate the contributions from tidal (<1.5 days) and eddy (2-35 days) components of the ocean heat transport to the basal melting of each ice shelf. In our simulation, the 2014 mean basal melt rate for TIS is 6.7 m yr-1 (42 Gt yr-1) and 9.7 m yr-1 (52 Gt yr-1) for MUIS. We find high wavelet coherence in the eddy dominated frequency band between the two ice shelves over almost the whole year. The wavelet coherence along five transects across the ice shelves suggests that TIS basal melting is dominated by eddy processes, while MUIS basal melting is dominated by tidal processes. The eddy-dominated basal melt for TIS is probably due to the large and convoluted bathymetric gradients beneath the ice shelf, weakening higher frequency tidal mode transport. This illustrates the key role of accurate bathymetric data plays in simulating on-going and future evolution of these important ice shelves.

Aerobic exercise and action observation priming modulate functional connectivity.

Aerobic exercise and action observation are two clinic-ready modes of neural priming that have the potential to enhance subsequent motor learning. Prior work using transcranial magnetic stimulation to assess priming effects have shown changes in corticospinal excitability involving intra- and interhemispheric circuitry. The objective of this study was to determine outcomes exclusive to priming- how aerobic exercise and action observation priming influence functional connectivity within a sensorimotor neural network using electroencephalography. We hypothesized that both action observation and aerobic exercise priming would alter resting-state coherence measures between dominant primary motor cortex and motor-related areas in alpha (7-12 Hz) and beta (13-30 Hz) frequency bands with effects most apparent in the high beta (20-30 Hz) band. Nine unimpaired individuals (24.8 ± 3 years) completed a repeated-measures cross-over study where they received a single five-minute bout of action observation or moderate-intensity aerobic exercise priming in random order with a one-week washout period. Serial resting-state electroencephalography recordings acquired from 0 to 30 minutes following aerobic and action observation priming revealed increased alpha and beta coherence between leads overlying dominant primary motor cortex and supplementary motor area relative to pre- and immediate post-priming timepoints. Aerobic exercise priming also resulted in enhanced high beta coherence between leads overlying dominant primary motor and parietal cortices. These findings indicate that a brief bout of aerobic- or action observation-based priming modulates functional connectivity with effects most pronounced with aerobic priming. The gradual increases in coherence observed over a 10 to 30-minute post-priming window may guide the pairing of aerobic- or action observation-based priming with subsequent training to optimize learning-related outcomes.

Advantages of Optical Coherence Tomography as a High Dynamic Range Imaging Modality in Subretinal Hyperreflective Material.

We aim to describe the utility of high dynamic range optical coherence tomography (OCT) imaging to study subretinal hyperreflective material (SHRM) in patients with age-related macular degeneration (AMD). We retrospectively reviewed clinical information including visual acuity (VA) and OCT images (Heidelberg Engineering Inc., Germany) of patients undergoing antiangiogenic treatment for neovascular AMD and showing SHRM at baseline. We increased contrast between strong signal structures (high dynamic range image) re-classifying SHRM as hyperreflective, isoreflective and hyporeflective. We evaluated the patients at baseline, 3, 6 and 12-months follow-up. Forty-four eyes were classified as 15 hyperreflective (34.1%); 21 as isoreflective (47.7%); and 8 as hyporeflective (18.2%). During follow-up, hyporeflective SHRM disappeared in all cases, isoreflective SHRM faded in 16 cases (76,2%); hyperreflective SHRM remained in all cases. Hyporreflective SHRM showed a greater VA improvement than hyperreflective SHRM group (p=0,033). After 12-month follow-up only the hyporeflective and isoreflective groups significantly reduced the presence of fluid in 37,5% (p=0,250) and 46,62% (p=0,006) of the patients respectively; and outer retinal layers were disrupted more frequently in the presence of hyperreflective SHRM (ellipsoid zone, p=0,16; external limiting membrane, p=0,007). Contrast-enhanced OCT images enabled us to classify SHRM according to its reflectivity showing groups with different disappearance rates, visual acuity improvement and outer retinal layer disruption. This easy to access tool may be helpful as a prognostic factor in neovascular AMD cases.

Characterisation of engineered defects in extreme ultraviolet mirror substrates using lab-scale extreme ultraviolet reflection ptychography

Ptychography is a lensless imaging technique that is aberration-free and capable of imaging both the amplitude and the phase of radiation reflected or transmitted from an object using iterative algorithms. Working with extreme ultraviolet (EUV) light, ptychography can provide better resolution than conventional optical microscopy and deeper penetration than scanning electron microscope. As a compact lab-scale EUV light sources, high harmonic generation meets the high coherence requirement of ptychography and gives more flexibilities in both budget and experimental time compared to synchrotrons. The ability to measure phase makes reflection-mode ptychography a good choice for characterising both the surface topography and the internal structural changes in EUV multilayer mirrors. This paper describes the use of reflection-mode ptychography with a lab-scale high harmonic generation based EUV light source to perform quantitative measurement of the amplitude and phase reflection from EUV multilayer mirrors with engineered substrate defects. Using EUV light at 29.6nm from a tabletop high harmonic generation light source, a lateral resolution down to ∼88nm and a phase resolution of 0.08rad (equivalent to topographic height variation of 0.27nm) are achieved. The effect of surface distortion and roughness on EUV reflectivity is compared to topographic properties of the mirror defects measured using both atomic force microscopy and scanning transmission electron microscopy. Modelling of reflection properties from multilayer mirrors is used to predict the potential of a combination of on-resonance, actinic ptychographic imaging at 13.5nm and atomic force microscopy for characterising the changes in multilayered structures.

Dual-comb fiber laser for stable frequency distribution.

A passive dual-comb laser can generate two optical frequency combs with different repetition frequencies. These repetition differences have high relative stability and mutual coherence through passive common-mode noise suppression without complex tight phase locking from a single-laser cavity. The comb-based frequency distribution requires the dual-comb laser to have a high repetition frequency difference. This paper presents a high repetition frequency difference bidirectional dual-comb fiber laser based on an all-polarization-maintaining cavity configuration and a semiconductor saturable absorption mirror with single polarization output. The proposed comb laser has a standard deviation of 69 Hz and an Allan deviation of 1.17 × 10-7 at τ = 1 s under different repetition frequencies of 12.815 MHz. Moreover, a transmission experiment has been conducted. Owing to the passive common-mode noise rejection capability of dual-comb laser, after passing an 84 km fiber link, the frequency stability of the repetition frequency difference signal is improved by two orders of magnitude than the repetition frequency signal at the receiver side.

Dynamic intrinsic spectrum reconstruction of narrow-linewidth laser based on band-extended frequency noise

Narrow-linewidth lasers have extensive applications due to advantages of low phase noise and high coherence. To explore the dynamics of narrow-linewidth lasers, the intrinsic spectrum is a kernel parameter which can show the dynamical coupling strength between the spontaneous emission and the stimulated emission in a laser cavity. Herein, we propose an intrinsic spectrum measurement method of narrow-linewidth lasers based on the band-extended frequency noise, which can improve the spectrum resolution. In the experiment, we successfully apply the method to the measure the linewidth compression dynamics of external-cavity distributed feedback lasers. The proposed measurement method can dynamically characterize the fast evolution process of the laser intrinsic spectrum with wide-range linewidth fluctuations, which will benefit for the dynamics research of narrow-linewidth lasers and tunable lasers.

Correlation between resource-generating powers of quantum gates

We analyze the optimal basis for generating the maximum relative entropy of quantum coherence by an arbitrary gate on a two-qubit system. The optimal basis is not unique, and the high quantum coherence generating gates are also typically high entanglement generating ones and vice versa. However, the profile of the relative frequencies of Haar random unitaries generating different amounts of entanglement for a fixed amount of quantum coherence is different from the one in which the roles of entanglement and quantum coherence are reversed, although both follow the beta distribution.

Mapping User Experience Information Overload Problems Across Disciplines

User Experience (UX) has been increasing linearly with the systems and digital media. UX concept describes a human factor as an experience with the life cycle of digital technology. UX increases the usability of the product in the industry more than functionality. Interest in UX has produced a huge amount of product and research articles. Moreover, this interdisciplinary topic becomes increased significantly because of the wider applications. However, this benefit become a problem due to the number of publications. The information overload problem is the result of the increasing UX topic. Several researchers solved this problem with qualitative analysis, but it cannot solve the overload problem. In this paper, we purposed bibliometric analysis and research profiling to interpret UX information on the map, with the publications from 1998-2022, a dataset compiled in RIS format to provide article metadata. As a result, the UX information map from the topic with the five clusters. Therefore, to provide information on the topic's coherence, we propose a coupling network. A related topic is shown as a link; a direct link means high coherence between topics. The analysis was carried out using the 5W1H approach (what, where, who, when, why, and how). The results show that UX is indeed an interdisciplinary field, especially with a design approach and user experience. In addition, to determine novice researchers, determining the focus of research can be done by taking into account previous research goals and maps.

Production process networks: a trophic analysis

In this article, production process databases originating from environmental sciences, more specifically from life cycle inventory (LCI), are considered as bipartite directed random networks. To model the observed directed hierarchical connection patterns, we turn to recent development concerning trophic coherence. Extending the scope to include bipartite networks, we compare several LCI networks to networks from other fields, and show empirically that they have high coherence and belong to the loopless regime, or close to its boundary.

Multiscale Phase-Contrast Tomography at BM18

Synchrotron phase-contrast micro-tomography is considered the gold standard in non-destructive volumetric imaging of millimeter and centimeter-sized objects. Micro-tomography beamlines are operating at many synchrotron radiation facilities, including the Extremely Brilliant Source (EBS) at the European Synchrotron Radiation Facility (ESRF). Applications favor objects which cannot be sufficiently resolved by state-of-the-art industrial micro-CT scanners. Synchrotron tomography features much superior time resolution, e.g., for in situ micro-CT, as well as superior photon flux, thus making this method suitable for Region of Interest scanning (i.e., multiresolution tomography). This report presents first results from the EBS' latest industrial beamline BM18, which was built for hierarchical propagation phase-contrast tomography. BM18 makes use of the exceptionally high coherence of the new ESRF-EBS lattice. Thanks to the wide polychromatic high-energy beam, one can scan and zoom into larger parts, e.g., from additive manufacturing or battery packs. In particular, BM18 allows for recording multiple scans at different resolutions ranging from 42 μm down to 0.6 μm, without the need to remove the object or manually change detectors. Free space propagation of up to 36 m yields excellent phase-contrast which in turn enhances the resolving power of the system. BM18 is generating an unprecedented amount of very large datasets. Consequently, novel strategies for data processing, storage and visualization are under development for this particular instrument.

Radar Band Fusion Using Frame-Based Compressed Sensing

Existing compressed sensing algorithms fail when applied to radar target detection in the presence of a large gap in the frequency band, i.e., presence of signals in separate, discontinuous bands. A new algorithm based on a subdivision-fusion scheme is proposed to solve this problem. The main goal is to use a structured sensing matrix based on radar signals to an advantage and obtain a good range resolution in spite of high coherence. Parameters influencing the performance of the algorithm are discussed. Simulative examples and results based on real measurement data are presented. The results show superior performance of the proposed method in the presence of band gaps.

Belief Inflexibility and Cognitive Biases in Anorexia Nervosa-The Role of the Bias against Disconfirmatory Evidence and Its Clinical and Neuropsychological Correlates.

The aim of this study was to explore, in a sample of patients with a diagnosis of AN, the ability to question their first impression and, in particular, the willingness to integrate their prior ideas and thoughts with additional progressive incoming information. A total of 45 healthy women and 103 patients with a diagnosis of AN, consecutively admitted to the Eating Disorder Padova Hospital-University Unit, underwent a broad clinical and neuropsychological assessment. All participants were administered the Bias Against Disconfirmatory Evidence (BADE) task, which specifically investigates belief integration cognitive bias. Acute AN patients showed a significantly greater bias toward disconfirming their previous judgment, in comparison to healthy women (BADE score, respectively, 2.5 ± 2.0 vs. 3.3 ± 1.6; Mann-Whitney test, p = 0.012). A binge-eating/purging subtype of AN individuals, compared to restrictive AN patients and controls, showed greater disconfirmatory bias and also a significant propensity to uncritically accept implausible interpretations (BADE score, respectively, 1.55 ± 1.6 and 2.70 ± 1.97 vs. 3.33 ± 1.63; Kruskal-Wallis test, p = 0.002 and liberal acceptance score, respectively, 1.32 ± 0.93 and 0.92 ± 1.21 vs. 0.98 ± 0.75; Kruskal-Wallis test p = 0.03). Abstract thinking skills and cognitive flexibility, as well as high central coherence, are neuropsychological aspects positively correlated with cognitive bias, in both patients and controls. Research into belief integration bias in AN population could enable us to shed light on hidden dimensional aspects, facilitating a better understanding of the psychopathology of a disorder that is so complex and difficult to treat.

Distributed optical fiber sensing system based on semiconductor lasers with mutual unbalanced double optical injection

A distributed optical fiber sensing system based on semiconductor lasers with mutual unbalanced double optical injection is proposed. Unequal lengths of the two injection paths enhance the nonlinear effect of the laser. The optical phase modulation caused by an external vibration acting on the sensing fiber is converted into the intensity modulation by the unbalanced double optical injection effect of the laser. Based on the synchronization effect of the mutually injected lasers, two waveform changes corresponding to the same external vibration emerge in the output signal of the system. The vibration position can be determined by the time difference between the two waveform changes. The period-one state of the system is employed to reduce the influence of optical phase noise and improve the sensing performance. The sensing system is modeled based on the rate equations of the mutually injected semiconductor lasers, and the working principle of the system is validated by numerical simulation. The location performance of the system is investigated experimentally. The average location error is less than 11 m on the 3.7 km-long sensing fiber. The experimental results show that the proposed system can work stably with a simple and accurate location method and does not require high coherence of the light source.

Supercontinuum generation in chalcogenide photonic crystal fiber infiltrated with liquid

Chalcogenide fibers have attracted much attention for multi-octave spanning supercontinuum generation in the mid-infrared range. However, readily optimizing the dispersion characteristics as well as other mode properties is still problematic because it is difficult to fabricate chalcogenide fibers with sophisticated structures. In this work, we numerically investigate the liquid infiltration as a post-processing method to optimize the dispersion shapes, so that the nonlinear dynamics and spectro-temporal properties of supercontinuum generation are efficiently controlled. In particular, water, carbon disulfide (CS2), carbon tetrachloride (CCl4), and bromoform (CHBr3) are selected to fill into all cladding air holes of As38Se62 fibers for dispersion engineering. By pumping a femtosecond laser at 4.5 μm, pulse duration of 250 fs, and pulse energy of 0.1 nJ (peak power of 0.4 kW), the unfilled and CCl4-filled fibers provide soliton-induced supercontinuum generation with a spectral bandwidth of 2.5–6.5 μm and 2.0–5.5 μm, respectively. Whilst, CHBr3-filled fiber offers all-normal dispersion supercontinuum generation with high coherence and spectral bandwidth of 2.2–5.2 μm. In contrast, unfortunately, CS2 and water-filled fibers have complex dispersion shapes and provide narrow bandwidth supercontinua. We also thoroughly numerically investigate the tapered fibers, which assure both high coupling efficiency with laser sources and high nonlinearity, for broad mid-infrared supercontinuum generation. The results point out that liquid-filled tapered fibers can provide both anomalous and all-normal dispersion SC generation with an octave-spanning bandwidth via the same value of input peak power (0.4 kW). With a large core diameter (12 μm) at the input and output fiber ends, the tapered fibers have a potential to couple with high-power laser pulses without fiber damage, therefore, they can provide supercontinuum spectra with broad bandwidth and high spectral power density for practical applications in sensing, gas detection, and LIDAR.

Characteristic Scales of Complexity and Coherence within Interplanetary Coronal Mass Ejections: Insights from Spacecraft Swarms in Global Heliospheric Simulations

Many aspects of the 3D structure and evolution of interplanetary coronal mass ejections (ICMEs) remain unexplained. Here, we investigate two main topics: (1) the coherence scale of magnetic fields inside ICMEs, and (2) the dynamic nature of ICME magnetic complexity. We simulate ICMEs interacting with different solar winds using the linear force-free spheromak model incorporated into the EUHFORIA model. We place a swarm of ∼20,000 spacecraft in the 3D simulation domain and characterize ICME magnetic complexity and coherence at each spacecraft based on the simulated time series. Our simulations suggest that ICMEs retain a lower complexity and higher coherence along their magnetic axis, but that a characterization of their global complexity requires crossings along both the axial and perpendicular directions. For an ICME of initial half angular width of 45° that does not interact with other large-scale solar wind structures, global complexity can be characterized by as little as 7–12 spacecraft separated by 25°, but the minimum number of spacecraft rises to 50–65 (separated by 10°) if interactions occur. Without interactions, ICME coherence extends for 45°, 20°–30°, 15°–30°, and 0°–10° for B, B ϕ , B θ , and B r , respectively. Coherence is also lower in the ICME west flank compared to the east flank due to Parker spiral effects. Moreover, coherence is reduced by a factor of 3–6 by interactions with solar wind structures. Our findings help constrain some of the critical scales that control the evolution of ICMEs and aid in the planning of future dedicated multispacecraft missions.

Micro-Computed Tomography Beamline of the Australian Synchrotron: Micron-Size Spatial Resolution X-ray Imaging

The first new beamline of the BRIGHT project—involving the construction of eight new beamlines at the Australian Synchrotron—is the Micro-Computed Tomography (MCT) beamline. MCT will extend the facility’s capability for higher spatial resolution X-ray-computed tomographic imaging allowing for commensurately smaller samples in comparison with the existing Imaging and Medical Beamline (IMBL). The source is a bending-magnet and it is operating in the X-ray energy range from 8 to 40 keV. The beamline provides important new capability for a range of biological and material-science applications. Several imaging modes will be offered such as various X-ray phase-contrast modalities (propagation-based, grating-based, and speckle-based), in addition to conventional absorption contrast. The unique properties of synchrotron radiation sources (high coherence, energy tunability, and high brightness) are predominantly well-suited for producing phase contrast data. An update on the progress of the MCT project in delivering high-spatial-resolution imaging (in the order of micron size) of mm-scale objects will be presented in detail with some imaging results from the hot-commissioning stage.

Generation of Circulating Cavity Magnon Polaritons

In a circulating cavity magnon polariton (quantized spin wave plus photon, resonating in a microwave chamber), the hybrid state and a noninteracting photonic state rotate in opposite directions---an important phenomenon for generating chiral states of electromagnetic modes in cavity magnonics and microwave engineering, to impart angular momentum upon standing waves. This study demonstrates the unidirectional nature of the mode propagation, paving the way for the generation of a high-power microwave beam with high coherence and narrow bandwidth. The authors also demonstrate how the unidirectional mode propagation results in nonreciprocity of the mode's transmission amplitudes and phases.

ModPalma: Conceptualization of a novel date palm midribs prefabricated enclosure wall panel

Despite the environmental and economic benefits of prefabrication, its applications in Egypt remain limited due to the lack of trained builders and manufacturers. However, prefabrication is actively adopted in traditional date palm midribs handicrafts industries such as furniture and light partitions. This paper launches novel versatile utilization to revive market of date palm midribs industry. Innovated date palm midribs-based prefabricated enclosure wall panel, ModPalma, is a stud frame panel made entirely from midribs without supporting timber frame. Conceptualization of ModPalma was conducted through reflecting design fundamentals of lignocellulose-based commercial wall panels on traditional prefabrication techniques employed by common craftsmen. Constructional efficiency was assessed by building a full-size panel and Finite Element Method structural analysis of the executed details. The completed free-standing panel, built by craftsman with usual tools, indicated the high sturdiness, durability, workability and coherence of the design. The digital structural analysis showed that design was safe under loads exceeding allowable axial and transverse loads of standard Structural Insulated panels. Further research is to address enhancing the panel’s structural and thermal performances, as well as investigating economic feasibility and marketing strategies needed to reintroduce ModPalma as cost-efficient and clever alternative to conventional wall panels.

Design of a single glass tube optical lens for soft X-ray laser decoherence

Laser has the advantages of high brightness, good monochromaticity, high coherence and good directionality, however, in some cases such as laser imaging and laser processing where only its high brightness or high monochromaticity is desired, the interference effect caused by high coherence can affect and limit its effective applications. In this work, a new single glass tube decoherence lens (SGTDL) is designed for soft X-ray laser decoherence through the simulation calculations. The simulation results show that an SGTDL with an entrance diameter of 5 mm, exit diameter of 0.6 mm and a length of 15 cm can effectively reduce the coherence of the X-ray laser with a wavelength of 10 nm and a beam waist radius of 1.25 mm. At the same time, the exit beam with a divergence range of 30–50 mrad is obtained at the SGTDL’s exit, and the transmission efficiency and gain in power density of the SGTDL are 78% and 52.74, respectively. For a laser beam with a wavelength of up to 1 nm, this model of SGTDL can maintain the transmission efficiency of the beam at more than 30%. This work also discusses the influence of the X-ray laser energy and the SGTDL’s length on the transmission performances of the SGTDL. The results show that the SGTDL designed according to the total reflection principle can meet the application requirements for laser decoherence in a range from the extreme ultraviolet to X-ray wavelength, and has a wide application prospect in X-ray laser imaging, laser processing, etc.