We report on efficient passively Q-switched operation of an Yb:YAl3(BO3)4 laser with a 2D MoS2 acting as a saturable absorber, which is the first demonstration of passive Q-switching induced by 2D saturable absorbers in the Yb-ion crystal laser. An average output power of 1.52 W at 1039.6 nm is produced at a pulse repetition rate of 585 kHz, with optical-to-optical and slope efficiencies being 29.3%

The noise scale factor (NSF) is useful in calculating the random errors of lidar signals. A new method is proposed for estimating the NSF of lidar systems. Instead of measuring the solar background in the traditional method that demands special experiments or additional devices, the new method utilizes the molecular backscattered signal fragments of routinely observed lidar profiles to extract the

A tunable half-open cavity multi-wavelength erbium-doped random distributed feedback (RDFB) fiber laser is proposed and experimentally demonstrated. The backward Rayleigh scattering generated by inhomogeneous reflective in the 25-km-long single mode fiber is amplified by the 8-m-long pumped erbium-doped fiber (EDF). The dual-pass Mach–Zehnder interferometer (MZI) acts as the reflection mirror in the

In order to reveal the operating characteristics of the pumpjet propulsor, standard k–𝜀, standard k–ω, RNG k–𝜀 and SST k–ω turbulence models were used to conduct steady calculation for the whole flow channels. By comparing the calculation results with experimental data, it was found that the calculation errors were very large in some operating conditions. Therefore, the uncertainty analysis was carried

Social networks are made up of members in society and the social relationships established by the interaction between members. Community structure is an essential attribute of social networks. The question arises that how can we discover the community structure in the network to gain a deep understanding of its underlying structure and mine information from it? In this paper, we introduce a novel community

A complex tanh-function method is presented for constructing optical soliton solutions for quadratic–cubic nonlinear medium. In addition, an ansätze is proposed for obtaining soliton solutions of the dimensionless form of the nonlinear Schrödinger’s equation that governs the propagation of solitons through optical fibers.

The specific structure of heterodyne detection system confocal microscopy (HDSCM) is presented in this paper. The theoretical derivation reveals that, HDSCM has the same transverse and axial resolutions as direct detection system confocal microscopy (DDSCM). However, HDSCM has several advantages over DDSCM. First, HDSCM does not need the conjugate pinhole which is necessary in DDSCM, thereby avoiding

In this work, a novel approximate closed-form probability density function for the sum of Gamma–Gamma random variates with Rayleigh pointing errors is derived by means of the well-known Jensen’s inequality. We employ the Kolmogorov–Smirnov goodness-of-fit statistical tests to verify the accuracy of the proposed approximation. The test results demonstrate that an exact distribution can be efficiently

Outdoor wireless communication is subject to several outdoor environment conditions. Among them, atmospheric turbulence which happens on a daily basis, introduces signal fading and degrades the system performance. Many channel models have been proposed in the literature to model the turbulence fading in free space optic (FSO) communication systems. In this work, we aim to evaluate the performance of

In this paper, a novel method has been proposed for increasing the extinction ratio of a plasmonic waveguide polarizer. Aluminum was coated in a 20-micron multi-strip pattern on the top of a SU-8 waveguide to excite the surface plasmons. The simulation and experimental results showed that the extinction ratio of the multi-strip polarizer was more than those of single-strip polarizers with the same

Aiming at the location problem of high-pressure pipeline leakage, this paper proposes a method for predicting the disturbed position of a Sagnac distributed optical fiber sensing system based on ensemble learning of convolutional neural networks (CNNs). A Stacking ensemble method is used to combine two different CNN models to improve the stability and location accuracy of the disturbance position prediction

A blue light emitting diode (LED) chip has been facilely fabricated on a 4-inch patterned sapphire substrate based on an InGaN/GaN multiple quantum well structure, composed of a Ce3+ doped Yttrium Aluminum Garnet (YAG) yellow phosphor packaged into a white LED chip. The epitaxial growth, fabrication, and package process of the device have been briefly described; the structural properties and device

Electromagnetic fields in light waves are mainly transverse to propagation direction but actually also have longitudinal components, which may give rise to unexpected optical phenomena involving the angular momentum of light, such as transverse spin and optical torques.

Many studies have shown the benefits of augmented reality (AR) to improve manufacturing and control processes in industry. However, the presentation of AR content through optical see-through head-mounted displays may induce unnatural viewing conditions, which consequences on the user’s visual system have not been investigated yet. This study aimed at assessing whether using AR instructions to guide

In this letter we present a fast triple voltage quenching circuit (TVQC) with an integrated $40~\mu \text{m}$ diameter single-photon avalanche diode (SPAD) in 0.35- $\mu \text{m}$ CMOS. By pre-biasing the switching MOSFETs the reaction time of the TVQC is kept small, leading to a total quenching time of only 1.4 ns of which 0.61 ns are actively quenched. This short reaction time reduces the avalanche

We investigate the flexibility of a LUT-based hierarchical DM for Probabilistic Constellation Shaping providing flexible net bit rates. Using a fixed parallelized input and output LUT-based architecture, including a flexible strategy to organize the input bits in each LUT, the proposed scheme shows an efficient performance in terms of rate loss vs. complexity, resulting in a DM solution to enable flexible

A polymer waveguide mode selecting switch (MSS) composed of two cascaded MMI couplers is demonstrated. The MSS can switch different data channels over $\text{E}_{\mathbf {00}}$ and $\text{E}_{\mathbf {10}}$ modes. Polymer waveguide dimensions are optimized with beam propagation method. The simulated results indicate that the worst insertion loss is 5.5 dB at 1550 nm and the switching powers for $\text{E}_{\mathbf

Carrier-induced anti-guiding effects emerging at extremely high injection current densities under short-pulse operation necessitate lateral-waveguide design considerations, that differ from those required when continuous-wave operation is desired. Here, we investigate variations of the lateral index-guiding trench design to achieve an excellent brightness value of 27.4 Wmm −1 mrad −1 from tapered-ridge-waveguide

Single-mode VCSELs have been demonstrated with great transmission capability over multimode fibers in the literature through restricted launch, which is beyond what is allowed by the effective modal bandwidth (EMB) defined for multimode transmission with the encircled flux launch condition. However, the impact of fiber index profile errors and their interactions with launch conditions have not been

Grating coupling is a widely adopted strategy for coupling light into optical waveguides. While this versatile approach benefits both fabrication and alignment, grating couplers are particularly sensitive to both wavelength and polarization. These drawbacks hinder its application in integrated wavelength-division-multiplexing passive optical network (WDM-PON) transceivers, where widely separated wavelength

We present the machine learning inspired design of two types of GaN zero contrast subwavelength gratings (SWGs): a polynomial-shaped grating and, for reference, a conventional rectangular grating, using the differential evolution algorithm to optimize the designs for high broadband reflectivity and separately for large fabrication tolerance. Two wavelength regimes with 500 nm and 1.55 μm center wavelengths

A method to calibrate the errors of polarization information measured by division-of-focal-plane polarimeters is demonstrated. The principle of this method is explained, and its feasibility is verified by theoretical simulation and experiment. The simulation and experimental results show that this method can obviously improve the measuring precision of polarization information, and compared with other

The state-of-the-art optical coherence technology (OCT) has its limitation, such as bulky and quite expensive. Miniaturization and integration of the OCT system are promising to get a compact, less costly, and more stable device. In this paper, we report the influence of optical power splitting on the sensitivity and axial resolution in spectral-domain OCT (SD-OCT) on silicon chip using tandem Mach-Zehnder

Early stage cancer detection technologies can provide functional information and potentially decrease the mortality rate caused by cervical cancer. In our previous work, a miniaturized ultrasound and photoacoustic endoscopic system has been developed to image the cervical tissue through the cervical canal to fulfills the need for a safe, low-cost, and high-resolution functional diagnostic system. However

An optical approach for pigmented lesions detection in human skin is presented. As differences between normal skin tissue and pigmentation tissue (and even a change in pigmentation development) can be detected by their optical properties, this paper presents a new, potentially noninvasive approach for skin cancer detection. Since each wavelength has different penetration depth into the tissue and different

To advancement in security applications, for the first time, a bio-chaotic key generated from the emerging biometric trait “finger knuckle print (FKP)” has been proposed for data security and authentication. In the system, the feasibility to generate multiple keys from the single FKP image has been exploited to secure multiple information, which results in significant enhancement of the security strength

In this work, we propose and numerically investigate a scheme for reservoir computing (RC) based on two parallel reservoirs under identical electrical message injection, in which two semiconductor lasers (SLs) under optical feedback are utilized as two parallel reservoirs. For simplifying the system, only one mask signal is employed in this scheme. After multiplying with input data, the masked information

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared

The KM3NeT infrastructure consists of two deep-sea neutrino telescopes being deployed in the Mediterranean Sea. The telescopes will detect extraterrestrial and atmospheric neutrinos by means of the incident photons induced by the passage of relativistic charged particles through the seawater as a consequence of a neutrino interaction. The telescopes are configured in a three-dimensional grid of digital

With the development and maturity of nanofabrication technology, many nanostructures with specific electromagnetic characteristics and optical functions have been designed and demonstrated. Artificial materials with these special optical properties are known as metamaterials. In this paper, a metamaterial lens is proposed and characterized. After using the space transformation approach based on the

In the paper, a wide range displacement sensor based on the variable line-spacing (VLS) grating was proposed and its displacement characteristics at different temperature environments were measured. The VLS grating was inscribed by electron beam lithography method, and the sensor mechanical structure was designed and fabricated. A broadband light was irradiated to the VLS grating though a twin-core

In this paper, the dynamic mechanical properties of GH4720Li nickel-base alloy under a large temperature range and high and low strain rates were studied by the hot compression test. The difference of mechanical properties of GH4720Li alloy under high and low strain rates was analyzed from the perspective of microstructure. The hot compression test experimental results showed that the true stress of

In the recent article by Ha et al., a triplet–triplet annihilation (TTA)-based photon up-conversion (UC) mechanism was combined with a downshifting (DS) process to demonstrate a selective-harvesting semitransparent luminescent solar concentrator (LSC).(1) Both ultraviolet (UV) and red light are absorbed and converted into green light by downshifting and triplet–triplet annihilation up-conversion luminescence

Different practical applications have emerged in the last few years, requiring periodic and detailed inspections to verify possible structural changes. Inspections using Unmanned Aerial Vehicles (UAVs) should minimize flight time due to battery time restrictions and identify the terrain’s topographic features. In this sense, Coverage Path Planning (CPP) aims at finding the best path to coverage of

Brain–computer interfaces (BCIs) have been proven to be useful for stroke rehabilitation, but there are a number of factors that impede the use of this technology in rehabilitation clinics and in home-use, the major factors including the usability and costs of the BCI system. The aims of this study were to develop a cheap 3D-printed wrist exoskeleton that can be controlled by a cheap open source BCI

Acoustic Doppler Current Profiler (ADCP) sensors measure water inflows and are essential to evaluate the Flow Curve (FC) of rivers. The FC is used to calibrate hydrological models responsible for planning the electrical dispatch of all power plants in several countries. Therefore, errors in those measures propagate to the final energy cost evaluation. One problem regarding this sensor is its positioning

A new algorithm based on singular value decomposition (SVD) to remove cardiac contamination from trunk electromyography (EMG) is proposed. Its performance is compared to currently available algorithms at different signal-to-noise ratios (SNRs). The algorithm is applied on individual channels. An experimental calibration curve to adjust the number of SVD components to the SNR (0–20 dB) is proposed.

Formula Kite is an Olympic sport that mainly differs from other kitesurfing modalities for the use of a hydrofoil. It is considered an extreme sport due to the great technical ability required. Regarding performance, the variables that determine performance in a real competition situation have not been studied, and even less so with Olympic sailors. Therefore, the objective of this study was to determine

In this paper, the authors investigate the innovative concept of a dense wireless network supported by additional functionalities inspired by the human nervous system. The nervous system controls the entire human body due to reliable and energetically effective signal transmission. Among the structure and modes of operation of such an ultra-dense network of neurons and glial cells, the authors selected

The traditional cone penetration test system uses cable to transmit data; as the probe goes deeper into the ground, the length of the cable will become longer. This makes the installation of the test equipment more complicated, and excessively long cables cause signal distortion and seriously affect data accuracy. To simplify the experimental equipment and improve the accuracy of data acquisition,

The performance of vehicle safety systems depends very much on the accuracy of the signals coming from vehicle sensors. Among them, the wheel speed is of vital importance. This paper describes a new method to obtain the wheel speed by using Sin-Cos encoders. The methodology is based on the use of the Savitzky–Golay filters to optimally determine the coefficients of the polynomials that best fit the

Traditional rigid exoskeletons can be challenging to the comfort of wearers and can have large pressure, which can even alter natural hand motion patterns. In this paper, we propose a low-cost soft exoskeleton glove (SExoG) system driven by surface electromyography (sEMG) signals from non-paretic hand for bilateral training. A customization method of geometrical parameters of soft actuators was presented

Glaucoma causes total or partial loss of vision in 10% of people over the age of 70, increasing their fragility and isolation. It is characterised by the destruction of the optic nerve fibres, which may result from excessively high intraocular pressure as well as other phenomena. Diagnosis is currently reached through a combination of several checks, mainly of the eyes’ fundus, tonometry and gonioscopy

In this work, we have designed and simulated a graphene field effect transistor (GFET) with the purpose of developing a sensitive biosensor for methanethiol, a biomarker for bacterial infections. The surface of a graphene layer is functionalized by manipulation of its surface structure and is used as the channel of the GFET. Two methods, doping the crystal structure of graphene and decorating the surface

Quadcopters are widely used in a variety of military and civilian mission scenarios. Real-time online detection of the abnormal state of the quadcopter is vital to the safety of aircraft. Existing data-driven fault detection methods generally usually require numerous sensors to collect data. However, quadcopter airframe space is limited. A large number of sensors cannot be loaded, meaning that it is

This study used visible/near-infrared hyperspectral imaging (HSI) technology combined with chemometric methods to assess the freshness of pearl gentian grouper. The partial least square discrimination analysis (PLS-DA) and competitive adaptive reweighted sampling-PLS-DA (CARS-PLS-DA) models were used to classify fresh, refrigerated, and frozen–thawed fish. The PLS-DA model achieved better classification

More effective methods to detect bovine tuberculosis, caused by Mycobacterium bovis, in wildlife, is of paramount importance for preventing disease spread to other wild animals, livestock, and human beings. In this study, we analyzed the volatile organic compounds emitted by fecal samples collected from free-ranging wild boar captured in Doñana National Park, Spain, with an electronic nose system based