Development and Validation of the DOAC Score: A Novel Bleeding Risk Prediction Tool for Patients With Atrial Fibrillation on Direct-Acting Oral Anticoagulants.

BACKGROUND: Current clinical decision tools for assessing bleeding risk in individuals with atrial fibrillation (AF) have limited performance and were developed for individuals treated with warfarin. This study develops and validates a clinical risk score to personalize estimates of bleeding risk for individuals with atrial fibrillation taking direct-acting oral anticoagulants (DOACs). METHODS: Among individuals taking dabigatran 150 mg twice per day from 44 countries and 951 centers in this secondary analysis of the RE-LY trial (Randomized Evaluation of Long-Term Anticoagulation Therapy), a risk score was developed to determine the comparative risk for bleeding on the basis of covariates derived in a Cox proportional hazards model. The risk prediction model was internally validated with bootstrapping. The model was then further developed in the GARFIELD-AF registry (Global Anticoagulant Registry in the Field-Atrial Fibrillation), with individuals taking dabigatran, edoxaban, rivaroxaban, and apixaban. To determine generalizability in external cohorts and among individuals on different DOACs, the risk prediction model was validated in the COMBINE-AF (A Collaboration Between Multiple Institutions to Better Investigate Non-Vitamin K Antagonist Oral Anticoagulant Use in Atrial Fibrillation) pooled clinical trial cohort and the Quebec Régie de l'Assurance Maladie du Québec and Med-Echo Administrative Databases (RAMQ) administrative database. The primary outcome was major bleeding. The risk score, termed the DOAC Score, was compared with the HAS-BLED score. RESULTS: Of the 5684 patients in RE-LY, 386 (6.8%) experienced a major bleeding event, within a median follow-up of 1.74 years. The prediction model had an optimism-corrected C statistic of 0.73 after internal validation with bootstrapping and was well-calibrated based on visual inspection of calibration plots (goodness-of-fit P=0.57). The DOAC Score assigned points for age, creatinine clearance/glomerular filtration rate, underweight status, stroke/transient ischemic attack/embolism history, diabetes, hypertension, antiplatelet use, nonsteroidal anti-inflammatory use, liver disease, and bleeding history, with each additional point scored associated with a 48.7% (95% CI, 38.9%-59.3%; P<0.001) increase in major bleeding in RE-LY. The score had superior performance to the HAS-BLED score in RE-LY (C statistic, 0.73 versus 0.60; P for difference <0.001) and among 12 296 individuals in GARFIELD-AF (C statistic, 0.71 versus 0.66; P for difference = 0.025). The DOAC Score had stronger predictive performance than the HAS-BLED score in both validation cohorts, including 25 586 individuals in COMBINE-AF (C statistic, 0.67 versus 0.63; P for difference <0.001) and 11 945 individuals in RAMQ (C statistic, 0.65 versus 0.58; P for difference <0.001). CONCLUSIONS: In individuals with atrial fibrillation potentially eligible for DOAC therapy, the DOAC Score can help stratify patients on the basis of expected bleeding risk.

Vision transformer empowered physics-driven deep learning for omnidirectional three-dimensional holography.

The inter-plane crosstalk and limited axial resolution are two key points that hinder the performance of three-dimensional (3D) holograms. The state-of-the-art methods rely on increasing the orthogonality of the cross-sections of a 3D object at different depths to lower the impact of inter-plane crosstalk. Such strategy either produces unidirectional 3D hologram or induces speckle noise. Recently, learning-based methods provide a new way to solve this problem. However, most related works rely on convolution neural networks and the reconstructed 3D holograms have limited axial resolution and display quality. In this work, we propose a vision transformer (ViT) empowered physics-driven deep neural network which can realize the generation of omnidirectional 3D holograms. Owing to the global attention mechanism of ViT, our 3D CGH has small inter-plane crosstalk and high axial resolution. We believe our work not only promotes high-quality 3D holographic display, but also opens a new avenue for complex inverse design in photonics.

The Isothermal Melting Kinetics of Ultra-High Molecular Weight Polyethylene Crystals.

The isothermal melting behaviors of ultra-high molecular weight polyethylene (UHMWPE) with different entangled states (i.e., nascent and melt-crystallized samples) are studied. For two kinds of UHMWPE samples, the result shows that the relative content of survived crystals (Xs) exponentially decreases with time and reaches a constant value. It is suggested that such a melting behavior is related to the observed nonlinear growth of crystals induced by the kinetically rejected entanglements accumulated at the growth front. Additionally, the exponential decay of Xs with time provides a characteristic melting time (τ) for the melting process. Compared to the melt-crystallized UHMWPE, the τ value of nascent UHMWPE is generally longer even in a higher temperature range, which is mainly because the former has a larger entanglement density difference. Furthermore, these observations demonstrate that UHMWPEs with different entangled states have an analogous melting mechanism since they exhibit a similar melting activation energy (≈1300 kJ mol-1).

Precision medicine analysis of heterogeneity in individual-level treatment response to amyloid beta removal in early Alzheimer's disease.

INTRODUCTION: Alzheimer's disease (AD) is a neurological disorder with variability in pathology and clinical progression. AD patients may differ in individual-level benefit from amyloid beta removal therapy. METHODS: Random forest models were applied to the EMERGE trial to create an individual-level treatment response (ITR) score which represents individual-level benefit of high-dose aducanumab relative to the placebo. This ITR score was used to test the existence of heterogeneity in treatment effect (HTE). RESULTS: We found statistical evidence of HTE in the Clinical Dementia Rating-Sum of Boxes (CDR-SB;P =  0.034). The observed CDR-SB benefit was 0.79 points greater in the group with the top 25% of ITR score compared to the remaining 75% (P = 0.020). Of note, the highest treatment responders had lower hippocampal volume, higher plasma phosphorylated tau 181 and a shorter duration of clinical AD at baseline. DISCUSSION: This ITR analysis provides a proof of concept for precision medicine in future AD research and drug development. HIGHLIGHTS: Emerging trials have shown a population-level benefit from amyloid beta (Aß) removal in slowing cognitive decline in early Alzheimer's disease (AD). This work demonstrates significant heterogeneity of individual-level treatment effect of aducanumab in early AD. The greatest clinical responders to Aß removal therapy have a pattern of more severe neurodegenerative process.

Estimation of DAPT Study Treatment Effects in Contemporary Clinical Practice: Findings From the EXTEND-DAPT Study.

BACKGROUND: Differences in patient characteristics, changes in treatment algorithms, and advances in medical technology could each influence the applicability of older randomized trial results to contemporary clinical practice. The DAPT Study (Dual Antiplatelet Therapy) found that longer-duration DAPT decreased ischemic events at the expense of greater bleeding, but subsequent evolution in stent technology and clinical practice may attenuate the benefit of prolonged DAPT in a contemporary population. We evaluated whether the DAPT Study population is different from a contemporary population of US patients receiving percutaneous coronary intervention and estimated the treatment effect of extended-duration antiplatelet therapy after percutaneous coronary intervention in this more contemporary cohort. METHODS: We compared the characteristics of drug-eluting stent-treated patients randomly assigned in the DAPT Study to a sample of more contemporary drug-eluting stent-treated patients in the National Cardiovascular Data Registry CathPCI Registry from July 2016 to June 2017. After linking trial and registry data, we used inverse-odds of trial participation weighting to account for patient and procedural characteristics and estimated a contemporary real-world treatment effect of 30 versus 12 months of DAPT after coronary stent procedures. RESULTS: The US drug-eluting stent-treated trial cohort included 8864 DAPT Study patients, and the registry cohort included 568 540 patients. Compared with the trial population, registry patients had more comorbidities and were more likely to present with myocardial infarction and receive 2nd-generation drug-eluting stents. After reweighting trial results to represent the registry population, there was no longer a significant effect of prolonged DAPT on reducing stent thrombosis (reweighted treatment effect: -0.40 [95% CI, -0.99% to 0.15%]), major adverse cardiac and cerebrovascular events (reweighted treatment effect, -0.52 [95% CI, -2.62% to 1.03%]), or myocardial infarction (reweighted treatment effect, -0.97% [95% CI, -2.75% to 0.18%]), but the increase in bleeding with prolonged DAPT persisted (reweighted treatment effect, 2.42% [95% CI, 0.79% to 3.91%]). CONCLUSIONS: The differences between the patients and devices used in contemporary clinical practice compared with the DAPT Study were associated with the attenuation of benefits and greater harms attributable to prolonged DAPT duration. These findings limit the applicability of the average treatment effects from the DAPT Study in modern clinical practice.

A Multifunctional Asymmetric Fabric for Sustained Electricity Generation from Multiple Sources and Simultaneous Solar Steam Generation.

Harvesting electrical energy from water and moisture has emerged as a novel ecofriendly energy conversion technology. Herein, a multifunctional asymmetric polyaniline/carbon nanotubes/poly(vinyl alcohol) (APCP) that can produce electric energy from both saline water and moisture and generate fresh water simultaneously is developed. The constructed APCP possesses a negatively charged porous structure that allows continuous generation of protons and ion diffusion through the material, and a hydrophilicity-hydrophobic interface which results in a constant potential difference and sustainable output. A single APCP can maintain stable output for over 130 h and preserve a high voltage of 0.61 V, current of 81 µA, and power density of 82.4 µW cm-3 with 0.15 cm3 unit size in the water-induced electricity generation process. When harvesting moisture energy, the APCP creates dry-wet asymmetries and triggers the spontaneous development of electrical double layer with a current density of 1.25 mA cm-3 , sufficient to power small electronics. A device consisting of four APCP can generate stable electricity of 3.35 V and produce clean water with an evaporation rate of 2.06 kg m-2  h-1 simultaneously. This work provides insights into the fabrication of multifunctional fabrics for multisource energy harvesting and simultaneous solar steam generation.

Days at home after transcatheter or surgical aortic valve replacement in high-risk patients.

BACKGROUND: Days at home (DAH) quantifies time spent at home after a medical event but has not been fully evaluated for TAVR. We sought to compare 1- and 5-year DAH (DAH365, DAH1825) among high-risk patients participating in a randomized trial of transcatheter aortic valve replacement (TAVR) with a self-expanding bioprosthesis versus surgical aortic valve replacement (SAVR). METHODS: We linked data from the U.S. CoreValve High Risk Trial to Medicare Fee-for-Service claims in 456 patients with 450 (234 TAVR/216 SAVR) and 427 (222 TAVR/205 SAVR) analyzed at 1 and 5 years. DAH was calculated as the number of days alive and spent outside of a hospital, skilled nursing facility, rehabilitation, long-term acute care hospital, emergency department, or observation stay. RESULTS: Mean DAH365 was higher in patients who underwent TAVR compared with SAVR (295.1 ± 106.9 vs 267.8 ± 122.3, difference in days 27.2 [95% CI 6.0, 48.5], P = .01). Compared with SAVR, TAVR patients had a shorter index length of stay (LOS) (7.4 ± 4.5 vs 12.5 ± 9.0, difference in days -5.1 [-6.5, -3.8], P < .001). The largest contributions to decreased DAH365 were mortality days and total facility days after discharge from the index hospitalization (mortality days-TAVR: 34.7 ± 93.1 vs SAVR: 48.0 ± 108.8, difference in days -13.3 [95% CI -32.1, 5.5], P = .17; total facility days-TAVR: 27.9 ± 47.4 vs SAVR: 36.7 ± 48.9, difference in days -8.8 [95% CI -17.8, 0.1], P = .05). Mean DAH1825 was numerically but not statistically significantly higher in TAVR (TAVR: 1154.2 ± 659.0 vs SAVR: 1067.6 ± 697.3, difference in days 86.6 [95% CI -42.3, 215.6], P = .19). Landmark analysis showed no difference in DAH from years 1 to 5 (TAVR: 1040.4 ± 477.5 vs SAVR: 1022.9 ± 489.3, P = .74). CONCLUSIONS: In the U.S. CoreValve High Risk Trial linked to Medicare, high-risk patients undergoing TAVR spend an average of 27 additional DAH compared with SAVR in the first year after the procedure due to a shorter index LOS and the additive effect of fewer but nonsignificantly different mortality and total facility days after discharge from the index hospitalization compared with SAVR. After the first year, both groups spend a similar number of DAH. These results describe the postprocedural course of high-risk patients from a patient-centered perspective, which may guide expectations regarding longitudinal health care needs and inform shared decision-making.

High-sensitivity optical fiber magnetic field sensor based on multimode optical fiber multi Fabry-Perot interference cavities.

A high-sensitivity optical fiber magnetic field sensor based on a multi-Fabry-Perot interference (F-P) cavity in an etched multimode optical fiber (MMF) was proposed. The MMF was etched along the fiber axis and a hole with the length of about 250 µm formed in the MMF. The multi-F-P cavity in the MMF is a sandwich structure, which is composed of UV glue, magnetic fluid and UV glue. The refractive index and effective cavity length of the magnetic fluid cavity change with the changing of the external magnetic field, which will result in changes of the reflection spectra of the multi-F-P. Thus, the external magnetic field could be detected by the changes of spectra. Experimental results showed that the high magnetic field sensitivity of 299.7 pm/mT and 0.164 dB/mT were obtained in the range of 0∼8 mT weak magnetic induction intensity by using the wavelength and intensity demodulations, respectively. The proposed sensor shows the potential applications in the magnetic field measurement in the weak magnetic environment.

In-situ monitoring of refractive index change during water-ice phase transition with a multiresonant fiber grating.

In-situ monitoring of refractive index changes during a liquid-solid phase transition is achieved by measurement of the transmission spectrum from a single tilted fiber Bragg grating immersed in water. Differential wavelength shifts of multiple mode resonances are used to eliminate cross-talk from temperature, throughout the phase transition, and from strains occurring after solidification. The measured sudden shift of refractive index at the phase transition is shown to be consistent with the expected difference from water to ice, in spite of the observed onset of compressive strain on the fiber by the frozen water. Beyond the obvious application to research on the dynamics of liquid-solid phase transitions, this work demonstrates the multiparameter measurement capabilities of multiresonant gratings.

Polarization-independent tilted fiber Bragg grating surface plasmon resonance sensor based on spectrum optimization.

We experimentally demonstrated polarization multiplexing schemes in a tilted fiber grating (TFBG) to achieve polarization-independent fiber-optic surface plasmon resonance (SPR) sensors. The first used two orthogonal polarized lights separated by a polarization beam splitter (PBS) that are p-polarized in polarization-maintaining fiber (PMF) and precisely aligned with the tilted grating plane, so as to achieve the transmission of p-polarized light in two opposite directions of the Au-coated TFBG to excite SPR. Alternatively, polarization multiplexing was also achieved by exploring two polarization components to achieve the SPR effect through a Faraday rotator mirror (FRM). The SPR reflection spectra are polarization-independent of the light source and any perturbations to fibers, which are explained by the superposition of p- and s-polarized transmission spectra in equal proportions. The spectrum optimization is presented to reduce the proportion of the s-polarization component. A polarization-independent TFBG-based SPR refractive index (RI) sensor with a wavelength sensitivity of 555.14 nm/RIU and an amplitude sensitivity of 1724.92 dB/RIU for small changes is obtained, exhibiting unique advantages of minimizing the polarization alterations by mechanical perturbations.

On-chip non-uniform geometric metasurface for multi-channel wavefront manipulations.

Metasurfaces integrated with waveguides have been recently explored as a means to control the conversion between guided modes and radiation modes for versatile functionalities. However, most efforts have been limited to constructing a single free-space wavefront using guided waves, which hinders the functional diversity and requires a complex configuration. Here, a new, to the best of our knowledge, type of non-uniformly arranged geometric metasurface enabling independent multi-channel wavefront engineering of guided wave radiation is ingeniously proposed. By endowing three structural degrees of freedom into a meta-atom, two mechanisms (the Pancharatnam-Berry phase and the detour phase) of the metasurface are perfectly joined together, giving rise to three phase degrees of freedom to manipulate. Therefore, an on-chip polarization demultiplexed metalens, a wavelength-multiplexed metalens, and RGB-colored holography with an improved information capacity are successively demonstrated. Our results enrich the functionalities of an on-chip metasurface and imply the prospect of advancements in multiplexing optical imaging, augmented reality (AR) holographic displays, and information encryption.

Glial fibrillary acidic protein and multiple sclerosis progression independent of acute inflammation.

BACKGROUND: The clinical relevance of serum glial fibrillary acidic protein (sGFAP) concentration as a biomarker of MS disability progression independent of acute inflammation has yet to be quantified. OBJECTIVE: To test whether baseline values and longitudinal changes in sGFAP concentration are associated with disability progression without detectable relapse of magnetic resonance imaging (MRI) inflammatory activity in participants with secondary-progressive multiple sclerosis (SPMS). METHODS: We retrospectively analyzed longitudinal sGFAP concentration and clinical outcome data from the Phase 3 ASCEND trial of participants with SPMS, with no detectable relapse or MRI signs of inflammatory activity at baseline nor during the study (n = 264). Serum neurofilament (sNfL), sGFAP, T2 lesion volume, Expanded Disability Status Scale (EDSS), Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT), and composite confirmed disability progression (CDP) were measured. Linear and logistic regressions and generalized estimating equations were used in the prognostic and dynamic analyses. RESULTS: We found a significant cross-sectional association between baseline sGFAP and sNfL concentrations and T2 lesion volume. No or weak correlations between sGFAP concentration and changes in EDSS, T25FW, and 9HPT, or CDP were observed. CONCLUSION: Without inflammatory activity, changes in sGFAP concentration in participants with SPMS were neither associated with current nor predictive of future disability progression.

Review on Cell Structure Regulation and Performances Improvement of Porous Poly(Lactic Acid).

Recent advances in the cell structure regulation and performances improvement of porous poly(lactic acid) materials (PPMs) are systematically reviewed in this feature article. First, the typical processing methods, including template method, non-solvent induced phase separation, freeze-drying, and supercritical CO2  foaming, of PPMs are introduced emphatically. Their various cell morphologies by different processing methods are summarized: finger-like, honeycomb-like, fiber-like, through cell, open cell, closed cell, ball-like, and flower-like. Meanwhile, the transformation among different cell morphologies as well as the changes in cell size and cell density, having impact on the performances, is described. Second, the influence of stereo-complex crystals on the cell structure of PPMs is emphatically reviewed. Furthermore, the relationships between cell structure and properties that includes mechanical properties, thermal stability, heat insulation, and hydrophobicity, are elaborated. Eventually, the issues of PPMs worthy of further study are discussed.

Diabetes Screening by Race and Ethnicity in the United States: Equivalent Body Mass Index and Age Thresholds.

BACKGROUND: Racial/ethnic minority populations in the United States have increased rates of diabetes compared with White populations. The 2021 guidelines from the U.S. Preventive Services Task Force recommend diabetes screening for adults aged 35 to 70 years with a body mass index (BMI) of 25 kg/m2 or greater. OBJECTIVE: To determine the BMI threshold for diabetes screening in major racial/ethnic minority populations with benefits and harms equivalent to those of the current diabetes screening threshold in White adults. DESIGN: Cross-sectional study. SETTING: NHANES (National Health and Nutrition Examination Survey), 2011 to 2018. PARTICIPANTS: Nonpregnant U.S. adults aged 18 to 70 years (n = 19 335). MEASUREMENTS: A logistic regression model was used to estimate diabetes prevalence at various BMIs for White, Asian, Black, and Hispanic Americans. For each racial/ethnic minority group, the equivalent BMI threshold was defined as the BMI at which the prevalence of diabetes in 35-year-old persons in that group is equal to that in 35-year-old White adults at a BMI of 25 kg/m2. Ranges were estimated to account for the uncertainty in prevalence estimates for White and racial/ethnic minority populations. RESULTS: Among adults aged 35 years with a BMI of 25 kg/m2, the prevalence of diabetes in Asian Americans (3.8% [95% CI, 2.8% to 5.1%]), Black Americans (3.5% [CI, 2.7% to 4.7%]), and Hispanic Americans (3.0% [CI, 2.1% to 4.2%]) was significantly higher than that in White Americans (1.4% [CI, 1.0% to 2.0%]). Compared with a BMI threshold of 25 kg/m2 in White Americans, the equivalent BMI thresholds for diabetes prevalence were 20 kg/m2 (range, <18.5 to 23 kg/m2) for Asian Americans, less than 18.5 kg/m2 (range, <18.5 to 23 kg/m2) for Black Americans, and 18.5 kg/m2 (range, <18.5 to 24 kg/m2) for Hispanic Americans. LIMITATION: Sample size limitations precluded assessment of heterogeneity within racial/ethnic groups. CONCLUSION: Among U.S. adults aged 35 years or older, offering diabetes screening to Black Americans and Hispanic Americans with a BMI of 18.5 kg/m2 or greater and Asian Americans with a BMI of 20 kg/m2 or greater would be equivalent to screening White adults with a BMI of 25 kg/m2 or greater. Using screening thresholds specific to race/ethnicity has the potential to reduce disparities in diabetes diagnosis. PRIMARY FUNDING SOURCE: Richard A. and Susan F. Smith Center for Outcomes Research in Cardiology.

Effect of reduction in brain amyloid levels on change in cognitive and functional decline in randomized clinical trials: An instrumental variable meta-analysis.

INTRODUCTION: Whether the reduction in brain amyloid beta (Aß) plaque alone may substantially slow cognitive and functional decline in patients with dementia or mild cognitive impairment due to Alzheimer's disease (AD) remains debated. METHODS: An instrumental variable meta-analysis was performed to infer the effect of change in positron emission tomography (PET)-measured Aß standardized uptake value ratio (SUVR) on cognitive and functional decline. RESULTS: Pooling data from 16 randomized trials demonstrates that each 0.1-unit decrease in PET Aß SUVR is associated with a reduction (95% confidence interval) by 0.09 (0.034-0.15), 0.33 (0.12-0.55), and 0.13 (0.017-0.24) point in the average change of the Clinical Dementia Rating-Sum of Boxes, the Alzheimer's Disease Assessment Scale-Cognitive Subscale, and the Mini-Mental State Examination, respectively. DISCUSSION: This meta-analysis provides statistically significant evidence of a likely causal relationship between a reduction in Aß plaque and a reduction in cognitive and functional decline in patients with AD. HIGHLIGHTS: A widely cited meta-analysis article concluded amyloid beta reduction does not substantially improve cognition. We identified data inconsistencies in the initial publication and found new trial data. We repeated the meta-analysis after correcting data inconsistencies and adding new trial data. Updated results suggested statistically significant clinical benefit of amyloid beta reduction. Amyloid beta is a viable biological target for the treatment and prevention of AD.

Effect of intensive versus limited monitoring on clinical trial conduct and outcomes: A randomized trial.

BACKGROUND: Regulatory agencies have endorsed more limited approaches to clinical trial site monitoring. However, the impact of different monitoring strategies on trial conduct and outcomes is unclear. METHODS: We conducted a patient-level block-randomized controlled trial evaluating the effect of intensive versus limited monitoring on cardiovascular clinical trial conduct and outcomes nested within the CoreValve Continued Access and Expanded Use Studies. Intensive monitoring included complete source data verification of all critical datapoints whereas limited monitoring included automated data checks only. This study's endpoints included clinical trial outcome ascertainment as well as monitoring action items, protocol deviations, and adverse event ascertainment. RESULTS: A total of 2,708 patients underwent transcatheter aortic valve replacement (TAVR) and were randomized to either intensive monitoring (n = 1,354) or limited monitoring (n = 1,354). Monitoring action items were more common with intensive monitoring (52% vs 15%; P < .001), but there was no difference in the percentage of patients with any protocol deviation (91.6% vs 90.4%; P = .314). The reported incidence of trial outcomes between intensive and limited monitoring was similar for mortality (30 days: 4.8% vs 5.5%, P = .442; 1 year: 20.3% vs 21.3%, P = .473) and stroke (30 days: 2.8% vs 2.4%, P = .458), as well as most secondary trial outcomes with the exception of bleeding (intensive: 36.3% vs limited: 32.0% at 30 days, P = .019). There was a higher reported incidence of cardiac adverse events reported in the intensive monitoring group at 1 year (76.7% vs 72.4%; P = .019). CONCLUSIONS: Tailored limited monitoring strategies can be implemented without influencing the integrity of TAVR trial outcomes.

Sensors for simultaneous measurement of temperature and humidity based on all-dielectric metamaterials.

In this study, a new type of sensors based on all-dielectric metamaterials that can measure temperature and relative humidity simultaneously was designed and theoretically analyzed in detail. The proposed metamaterial sensor consists of a quartz substrate in the bottom layer, polydimethylsiloxane (PDMS) in the middle layer, and a periodic silicon structure on the top layer. CST Studio Suite was used to determine the transmission spectrum of the metamaterials in the near-infrared band using finite integration, and two transmission dips were observed. Then, polyvinyl alcohol (PVA) was used as the humidity-sensitive material to be coated on the surface of this metamaterial sensor, and these two transmission dips were used to measure the temperature and relative humidity simultaneously. Simulation results showed that the sensitivities of the two dips to the temperature are -0.224 and -0.069 nm/°C, and the sensitivities to the relative humidity are -0.618 and -0.521 nm/%, respectively. Based on the sensitivity matrix, the temperature and the relative humidity can be measured simultaneously. The proposed sensor has the advantages of polarization insensitivity, small size and low loss, which makes it have many application potentials in various research fields, including physics, biology and chemical sensing.

Tunable dielectric metasurfaces by structuring the phase-change material.

Metasurfaces have made great progress in the last decade for generating miniature and integrated optical devices. The optical properties of metasurfaces can be tuned dynamically by integrating with phase-change materials. However, the efficiency of tunable metasurfaces remains a bit low, which is a disadvantage for the realistic applications of metasurfaces. Here, we demonstrate the tunable dielectric metasurfaces by structuring the phase-change material Ge2Sb2Te5. The unit cell of metasurface is composed of several Ge2Sb2Te5 nanopillars with different geometric parameters, and the incident light interacts with different nanopillars at diverse phases of Ge2Sb2Te5, leading to various functions. By elaborately arranging the Ge2Sb2Te5 nanopillars, various tunable optical devices have been realized, including tunable beam steering, reconfigurable metalens and switchable wave plate. The refractive direction, focal length and polarization state can be tuned through the phase transition of Ge2Sb2Te5. The phase-change metasurfaces based on Ge2Sb2Te5 nanostructures could be used in cameras, optical microscopy and adaptive optics.

Light transmission mechanisms in a SMF-capillary fiber-SMF structure and its application to bi-directional liquid level measurement.

Capillary fiber (CF) has been extensively investigated in a singlemode fiber (SMF)-CF-SMF (SCS) sensing structure since multiple light guiding mechanisms can be easily excited by simply tuning the air core diameter (cladding diameter) and length of the CF. Understanding the light guiding principles in an SCS structure is essential for improved implementation of a CF based fiber sensor. In this work, light guiding principles in a relatively large air core diameter (≥ 20 µm) and long length of CF (> 1 mm) are investigated theoretically and experimentally. It is found that both multimode interference (MMI) and Anti-Resonant Reflecting Optical Waveguide (ARROW) light guiding mechanisms are excited in the SCS structure in the transmission configuration. However, MMI dips are not observed in the spectrum for the air core diameters of CF smaller than 50 µm in the experiment due to large transmission loss in small air core CFs. Further experimental results demonstrate that a CF with a bigger air core diameter shows a higher sensitivity to curvature, and the highest sensitivity of -16.15 nm/m-1 is achieved when an CF-100 was used. In addition, a SMF-CF-20-CF-30-SMF (SCCS) structure is proposed for high sensitivity bi-direction liquid level measurement for the first time, to the best of our knowledge. Two types of ARROW dips (Dip-20 and Dip-30) are simultaneously excited in transmission, hence both liquid level and liquid flow direction can be detected by tracing the dip strength changes of Dip-20 and Dip-30, respectively.

Spatiotemporal self-mode-locked operation in a compact partial multimode Er-doped fiber laser.

We report spatiotemporal self-mode-locked operation at 1.55 µm with a low pump threshold of 32 mW in a compact partial multimode fiber laser system. Spatial filtering and the saturable absorber, both of which originate from the multimode interference (linear or nonlinear) of the single mode-multimode structure in this hybrid configuration, are well suited to the spatiotemporal self-mode-locked operation. Not only stable multimode conventional solitons with different spectral bandwidths but also a multimode soliton molecule complex with different structural bound-state patterns are obtained. It is found that the spatiotemporal evolution of the multimode solitons is dependent on many factors, such as the operating state, the involved frequency component, and the interaction between solitons. Furthermore, an unstable spatiotemporal mode-locked (STML) state where the beam profiles of the solitons change spontaneously is also observed for a specific multimode fiber state and pump power.