Gigahertz femtosecond laser-by a novel asymmetric one-dimensional photonic crystal saturable absorber device with defect layer.

High repetition frequency (HRF) ultrashort pulse fiber laser has been widely used in laser cold processing. The technical solutions such as short cavity length fiber laser have been proposed to achieve HRF ultrashort pulse output recently. However, the application of material-based saturable absorbers in this field has been astricted due to the low modulation depth, low damage resistance threshold, and high saturation fluence.

Ultrafast photothermoelectric effect in Dirac semimetallic CdAs revealed by terahertz emission.

The thermoelectric effects of topological semimetals have attracted tremendous research interest because many topological semimetals are excellent thermoelectric materials and thermoelectricity serves as one of their most important potential applications. In this work, we reveal the transient photothermoelectric response of Dirac semimetallic CdAs, namely the photo-Seebeck effect and photo-Nernst effect, by studying the terahertz (THz) emission from the transient photocurrent induced by these effects. Our excitation polarization and power dependence confirm that the observed THz emission is due to photothermoelectric effect instead of other nonlinear optical effect.

Multifunctional terahertz metasurfaces for polarization transformation and wavefront manipulation.

Conventionally, the realization of polarization transformation and wavefront manipulation in metasurfaces relies on the Pancharatnam-Berry (PB) phase together with the dynamic phase. However, the reported polarization transformation and wavefront manipulation were limited to spin-dependent wavefront manipulation for circular polarization (CP). To obtain more abundant functions, we propose a novel technology that relies on the dynamic phase with a spatial interleaving unit arrangement.

Double-Antibody Sandwich Immunoassay and Plasmonic Coupling Synergistically Improved Long-Range SPR Biosensor with Low Detection Limit.

A long-range surface plasmonic resonance (LR-SPR) biosensor modified with double-antibody sandwich immunoassay and plasmonic coupling is demonstrated for human-immunoglobulin G detection with a low limit of detection (LOD). The double-antibody sandwich immunoassay dramatically changes the average refractive index of the medium layer on the sensor surface. The near-field electron coupling between the localized surface plasmon and the long-range surface plasmon leads to a significant perturbation of the evanescent field.

Visible to near-infrared photodetector based on SnSe/WSeheterojunction with potential application in artificial visual neuron.

Two-dimensional (2d) transition-metal dichalcogenides (TMDCs) are promising candidate materials for developing next generation nano optoelectronic devices, due to their strong interaction with light. In addition, the free of surface dangling bonds makes it possible to stacking any different types of 2D TMDCs together to form heterojunctions with desirable band structures for various applications. However, most of the 2D TMDCs are bipolar or strong unipolar n-type doped, while very few of them show weak p-type doping, which severely affects the performance of the formed heterojunctions.

Automatic lumen segmentation using uniqueness of vascular connected region for intravascular optical coherence tomography.

We present an automatic lumen segmentation method using uniqueness of connected region for intravascular optical coherence tomography (IVOCT), which can effectively remove the effect on lumen segmentation caused by blood artifacts. Utilizing the uniqueness of vascular wall on A-lines, we detect the A-lines shared by multiple connected regions, identify connected regions generated by blood artifacts using traversal comparison of connected regions' location, shared ratio and area ratio and then remove all artifacts. We compare these three methods by 216 challenging images with severe blood artifacts selected from clinical 1076 IVOCT images.

In-situ diagnostic of femtosecond laser probe pulses for high resolution ultrafast imaging.

Ultrafast imaging is essential in physics and chemistry to investigate the femtosecond dynamics of nonuniform samples or of phenomena with strong spatial variations. It relies on observing the phenomena induced by an ultrashort laser pump pulse using an ultrashort probe pulse at a later time. Recent years have seen the emergence of very successful ultrafast imaging techniques of single non-reproducible events with extremely high frame rate, based on wavelength or spatial frequency encoding.

All-dielectric chiral-field-enhanced Raman optical activity.

Raman optical activity (ROA) is effective for studying the conformational structure and behavior of chiral molecules in aqueous solutions and is advantageous over X-ray crystallography and nuclear magnetic resonance spectroscopy in sample preparation and cost performance. However, ROA signals are inherently minuscule; 3-5 orders of magnitude weaker than spontaneous Raman scattering due to the weak chiral light-matter interaction. Localized surface plasmon resonance on metallic nanoparticles has been employed to enhance ROA signals, but suffers from detrimental spectral artifacts due to its photothermal heat generation and inability to efficiently transfer and enhance optical chirality from the far field to the near field.

Dynamical evolution of anisotropic response of type-II Weyl semimetal TaIrTe under ultrafast photoexcitation.

Layered type-II Weyl semimetals, such as WTe, MoTe, and TaIrTe have been demonstrated as a supreme photodetection material with topologically enhanced responsivity and specific sensitivity to the orbital angular momentum of light. Toward future device applications with high performance and ultrafast response, it is necessary to understand the dynamical processes of hot carriers and transient electronic properties of these materials under photoexcitation. In this work, mid-infrared ultrafast spectroscopy is performed to study the dynamical evolution of the anisotropic response of TaIrTe.

UV light modulated synaptic behavior of MoTe/BN heterostructure.

Electrical synaptic devices are the basic components for the hardware based neuromorphic computational systems, which are expected to break the bottleneck of current von Neumann architecture. So far, synaptic devices based on three-terminal transistors are considered to provide the most stable performance, which usually use gate pulses to modulate the channel conductance through a floating gate and/or charge trapping layer. Herein, we report a three-terminal synaptic device based on a two-dimensional molybdenum ditelluride (MoTe)/hexagonal boron nitride (hBN) heterostructure.

Modulation of MoTe/MoS van der Waals heterojunctions for multifunctional devices using NO plasma with an opposite doping effect.

van der Waals layered heterojunctions have a variety of band offsets that open up possibilities for a wide range of novel and multifunctional devices. However, due to their poor pristine carrier concentrations and limited band modulation methods, multifunctional p-n heterojunctions are very difficult to achieve. In this report, we developed a highly effective N2O plasma process to treat MoTe2/MoS2 heterojunctions.

Fine manipulation of terahertz waves via all-silicon metasurfaces with an independent amplitude and phase.

Integrating independent wavefront controls into one device can meet the increasing demand for high-capacity flat electromagnetic devices. Simultaneously and independently controlling the amplitude and phase is pivotal for completely manipulating the propagation of electromagnetic waves. Here, we propose several all-silicon metasurfaces to achieve multifunctional designs and simultaneous modulation of amplitude and phase profiles in the terahertz (THz) band.

Bioinformatics analysis of Myelin Transcription Factor 1.

Background And Objective: We aimed to further study the role of Myelin Transcription Factor 1(MyT1) in tumor and other diseases and epigenetic regulation, and better understand the regulatory mechanism of MyT1.

Methods: Using bioinformatics analysis, the structure and function of MyT1sequence were predicted and analyzed using bioinformatics analysis, and providing a theoretical basis for further experimental verification and understanding the regulatory mechanism of MyT1. The first, second and third-level structures of MyT1 were predicted and analyzed by bioinformatics analysis tools.

Light-induced pyroelectric property of self-powered photodetectors based on all-inorganic perovskite quantum dots.

All-inorganic cesium lead bromine (CsPbBr) perovskites quantum dots (QDs) are one of the most photoelectric materials due to their high absorption coefficient, pronounced quantum-size effect, tunable optical property. Here, a self-powered PD based on all-inorganic CsPbBrperovskites QDs is fabricated and demonstrated. The light-induced pyroelectric effect is utilized to modulate the optoelectronic processes without the external power supply.

Dual-functional optoelectronic memories based on ternary hybrid floating gate layers.

Optoelectronic memories based on organic field-effect transistors (OFETs) have been extensively investigated, and great progress has been made in improving memory performance and reducing operating power consumption. Despite these achievements, optoelectronic memories reported so far have only a single storage function, such as light-assisted memory, light writing memory, or light-erasing memory, which may not meet the requirements of multi-functional storage in the future. Here, the dual-functional optoelectronic memories are demonstrated by employing ternary hybrid films as floating gate layers.

An iPPG-Based Device for Pervasive Monitoring of Multi-Dimensional Cardiovascular Hemodynamics.

Hemodynamic activities, as an essential measure of physiological and psychological characteristics, can be used for cardiovascular and cerebrovascular disease detection. Photoplethysmography imaging (iPPG) can be applied for such purposes with non-contact advances, however, most cardiovascular hemodynamics of iPPG systems are developed for laboratory research, which limits the application in pervasive healthcare. In this study, a video-based facial iPPG detecting equipment was devised to provide multi-dimensional spatiotemporal hemodynamic pulsations for applications with high portability and self-monitoring requirements.

Judd-Ofelt spectroscopic properties of Er-doped NaLa(WO) polycrystalline powder.

Er-doped NaLa(WO) is a promising phosphor material for applications in many fields including the ratiometric thermometry based on thermal effect of fluorescence intensity ratio (FIR) of green fluorescence of Er, which is directly correlated with Judd-Ofelt parameters Ω (i = 2, 4, 6). Present paper reports synthesis and Judd-Ofelt spectroscopic properties of Er-doped NaLa(WO) µm-sized phosphor. The phosphor was synthesized by solid-state chemical reaction and characterized by X-ray diffraction and Raman scattering techniques.

Three-dimensional spatial reconstruction of coronary arteries based on fusion of intravascular optical coherence tomography and coronary angiography.

We present a three-dimensional (3D) spatial reconstruction of coronary arteries based on fusion of intravascular optical coherence tomography (IVOCT) and digital subtraction angiography (DSA). Centerline of vessel in DSA images is exacted by multi-scale filtering, adaptive segmentation, morphology thinning and Dijkstra's shortest path algorithm. We apply the cross-correction between lumen shapes of IVOCT and DSA images and match their stenosis positions to realize co-registration.

Enhanced detectivity of PbS quantum dots infrared photodetector by introducing the tunneling effect of PMMA.

With extremely high optical absorption coefficient in infrared regime, lead sulfide (PbS) quantum dots (QDs)-based photodetectors are promising for diverse applications. In recent years, synthesis of materials has made great progress, but the problem of low sensitivity of quantum dots photodetector still unresolved. In this work, the introduction of a tunneling organic layer effectively address this problem.

Porous carbon nanowire array for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for vibrational spectroscopy as it provides several orders of magnitude higher sensitivity than inherently weak spontaneous Raman scattering by exciting localized surface plasmon resonance (LSPR) on metal substrates. However, SERS can be unreliable for biomedical use since it sacrifices reproducibility, uniformity, biocompatibility, and durability due to its strong dependence on "hot spots", large photothermal heat generation, and easy oxidization. Here, we demonstrate the design, fabrication, and use of a metal-free (i.

Multi-level flash memory device based on stacked anisotropic ReS-boron nitride-graphene heterostructures.

Charge-trapping memory devices based on two-dimensional (2D) material heterostructures possess an atomically thin structure and excellent charge transport capability, making them promising candidates for next-generation flash memories to achieve miniaturized size, high storage capacity, fast switch speed, and low power consumption. Here, we report a nonvolatile floating-gate memory device based on an ReS/boron nitride/graphene heterostructure. The implemented ReS memory device displays a large memory window exceeding 100 V, leading to an ultrahigh current ratio over 10 between programming and erasing states.

Impact of Equalization-Enhanced Phase Noise on Digital Nonlinearity Compensation in High-Capacity Optical Communication Systems.

Equalization-enhanced phase noise (EEPN) can severely degrade the performance of long-haul optical fiber transmission systems. In this paper, the impact of EEPN in Nyquist-spaced dual-polarization quadrature phase shift keying (DP-QPSK), dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM), and DP-64QAM optical transmission systems is investigated considering the use of electrical dispersion compensation (EDC) and multi-channel digital backpropagation (MC-DBP). Our results demonstrate that full-field DBP (FF-DBP) is more susceptible to EEPN compared to single-channel and partial-bandwidth DBP.

Refractometric Sensitivity Enhancement of Weakly Tilted Fiber Bragg Grating Integrated with Black Phosphorus.

The sensitivity enhancement of the weakly tilted fiber Bragg grating (WTFBG) integrated with black phosphorus (BP) was investigated via numerical simulations and experimental demonstrations. BP nanosheets were deposited twice on the cylindrical WTFBG surface using the in situ layer-by-layer (i-LbL) deposition technique. The resonance intensity of the deepest cladding mode located around 1552 nm of WTFBG had a 9.