To control the polarization of 850 nm multi-mode oxide-confined vertical-cavity surface-emitting lasers (VCSELs), monolithically integrated surface gratings are investigated. VCSELs with different grating parameters are simulated by the rigorous coupled-wave analysis (RCWA) method. Optical field intensity of two polarization orientations with different grating periods and duty cycles is obtained. The

Circular Airy Gaussian vortex (CAGV) beams have gained great popularity in areas of research such as optical tweezers and optical communications due to their fascinating properties, such as auto-focusing and self-healing. The propagation dynamics of these beams is dictated by their topological charge and launch angle. For example, larger topological charges and positive launch angles enhance the maximum

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

Broadband dual-comb spectroscopy (DCS) based on portable mode-locked fiber frequency combs is a powerful tool for in situ, calibration-free, multi-species spectroscopy. While the acquisition of a single spectrum with mode-locked DCS typically takes microseconds to milliseconds, the applications of these spectrometers have generally been limited to systems and processes with time changes on the order

We report a computational method based on deep learning (DL) to generate planar distributions of soot particles in turbulent flames from line-of-sight luminosity images. A conditional generative adversarial network (C-GAN) was trained using flame luminosity and planar laser-induced incandescence (LII) images simultaneously recorded in a turbulent sooting flame with an exit Reynolds number of 15,000

A technique for manipulating wavefronts of propagated objects is proposed, applying matrix algebra to data containing the amplitude and phase information of objects previously propagated. Matrices act as operators, altering the initial conditions of the propagated objects, such as their spatial coordinates, reflection effects, and changes in depth. In this work, we present the use of simple matrices

A diode-pumped acousto-optic Q-switched crystal Raman laser operating at multi-wavelength is reported, in which a c-cut Nd:YVO4 crystal was used as the self-Raman medium and a c-cut GdVO4 crystal was used as the other Raman medium. Benefited from the overlapping gain at the Raman shift of 259 cm−1 in the two crystals, the corresponding cascade Stokes light efficiently oscillated, and the 1177, 1178 nm

A hybrid feature selection method combining with wavelet transform (WT) was proposed to analyze the heat value of coal using laser-induced breakdown spectroscopy (LIBS). The hybrid feature selection method consisted of distance correlation (DC) method and recursive feature elimination with cross-validation (RFECV) method, which combined the advantages of DC-based filter method and RFECV-based wrapper

In an effort to find the optimal mid-wave infrared (MWIR) photodetector, Si-based GeSn heterojunction phototransistors (HPTs) were studied. The figure of merit (FOM) and noise-equivalent-power (NEP) of the proposed device were calculated the first time at different operating temperatures for MWIR applications. In addition, the impact of operating frequency on the detectivity and sensitivity of the

Micro-ring resonator (MRR)-based switching is one of the promising technologies in modern optical signal processing and optical computing. In this paper, we present a scheme of all-optical 2-bit ripple down counter, using the MRR-based all-optical switching activity. The proposed mechanism shows the generation of all-optical two bits ripple down sequences without any involvement of electrical pumping

According to the basic principle of the Herriott-type multi-pass cell (MPC), this paper analyzes the relationship between the optical path length (OPL) and the distance of the mirrors, and proposes a design method of variable optical path length MPC, which makes it easier to implement variable optical path length MPC. In the design, the incident angle is controlled to arrange the spots in a circle

The peak frequency of the terahertz radiation generated from the femtosecond laser-induced air plasmas is blue shifted with the increased second harmonics intensity when a high voltage is added upon the air plasmas. This blue shift is the result of the DC-biased field from the high voltage plus the AC-biased field from the second harmonics, indicating that this terahertz radiation frequency peak is

We propose an electro-optically controllable cascaded second-order optical process that mimics as a third-order nonlinear process which is utilized for the compression of ultrashort pulses. Effective compression of optical pulses has been achieved by making efficient use of frequency doubling into an extraordinarily advantageous crystal like beta-barium-borate which is capable of generating shorter

Large size single crystals of potassium L-ascorbate monohydrate, KC6H7O6.H2O (KLAM), are grown using solution growth technique by lowering the temperature at the rate of 0.24 °C/h, where water was used as a solvent. The structure of KLAM was solved by single-crystal XRD. KLAM crystallizes in P21 space group with unit cell parameters a = 7.030(5)Å, b = 8.811(5)Å, c = 7.638(5)Å and β = 114.891(5)°. The

Laser-induced breakdown spectroscopy (LIBS) has been evaluated for measurement of As, Hg, S, and Se in aqueous samples. Single pulse (SP) and double pulse (DP) LIBS, with a 1064 nm Nd: YAG laser source, were utilized to generate micro plasma from the surface of a liquid jet containing these elements. Plasma emission was collected at a 45° angle with the laser beam for As and Se detection in UV wavelength

In this paper, a trench-assisted large-mode-field-area multi-core fiber with an air-hole structure composed of 21 conventional fiber cores and 16 air holes is proposed, and it can realize dual-mode transmission. By adjusting the structural parameters, the effective mode field area of fundamental mode can be up to 1916.042 µm2 at 1550 nm. In addition, the fiber has good bending characteristics by adding

We have demonstrated significant improvement on the performance of a self-powered (zero power consumption) GaN ultraviolet photodetector (GaN-UVPD) under a 254-nm UV light exposure through the application of nickel nanoparticles (NiNPs). Indeed, the detectivity of the device increased from 2.81 × 1013 to 7.19 × 1013 cm Hz1/2 W−1 at 0 V, which is the highest reported detectivity of the self-powered

In this paper, a multi-band fusion model to improve the performances of the super-continuum laser absorption spectrometer (SCLAS) of CO2 was proposed and demonstrated. Various concentrations of CO2 were measured by the super-continuum laser in the wavelength of 1425–1445 nm, 1565–1585 nm, and 1595–1615 nm, respectively, at 295 K and 1 atm. The method for derivation of CO2 concentration using the integrated

Non-intrusive measurement techniques are required to gain a comprehensive understanding about the processes of soot formation, growth and oxidation. Time-resolved laser-induced incandescence (TiRe-LII), commonly performed 0D or 2D within a flame, has proven to be a very suitable tool for the in situ sizing of soot primary particles. In this work, the technique is expanded to the third dimension by

Laser-processing system plays an important role in modern processing. To improve the precision of a galvanometer laser-processing system, a novel compensation method based on machine vision is proposed. First, the various errors existing in the scanning process of the galvanometer system and the influence on the accuracy of the scanning system were analyzed. Second, processing a specific grid within

We report on the first continuous-wave quasi three-level laser emitting in the cyan-blue spectral range in praseodymium-doped oxide materials, as we believe. Pr:YAlO\(_3\) crystal, cooled to the cryogenic temperatures, was used as an active medium. To minimize resonator losses, the cavity mirrors were directly deposited on the crystal faces to form a microchip geometry. More than half-Watt of the output

A home-made small-sized Raman spectrometer combined with machine learning algorithms was used to study and identify healthy and multi-period osteoarthritis (OA) canine knee joints. Nine canines were equally divided into three groups according to the post-operative (OA modeling) time of 2-month, 3-month and 7-month. Other two normal canines were used as control. It was found that the degeneration degree

Two-dimensional laser-induced incandescence (LII) measurements usually involve the use of a cylindrical lens to illuminate the planar region of interest. This creates a varying laser fluence and sheet width in the imaged flame region which could lead to large uncertainties in the quantification of the 2D LII signals into soot volume fraction distributions. To investigate these effects, 2D LII measurements

A dual-frequency-comb spectrometer based on two quantum-cascade lasers is applied to kinetics studies of formaldehyde (HCHO) in a shock tube. Multispectral absorption measurements are carried out in a broad spectral range of 1740–1790 cm–1 at temperatures of 800–1500 K and pressures of 2–3 bar. The formation of HCHO from thermal decomposition of 1,3,5-trioxane (C3H6O3, 0.9% diluted in argon) and the

The epitaxial growth and emission properties of a membrane external-cavity surface-emitting laser (MECSEL) are demonstrated in the 1750 nm band. A heterostructure consisting of InGaAs quantum wells enclosed by InGaAlAs barriers was deposited on InP by molecular beam epitaxy. The emitted power exceeded 1.5 W, which is the highest that has been reported in this spectral range to date.

In this paper, the cholesterol concentration of human blood serum is qualitatively and quantitatively scrutinized via laser-induced breakdown spectroscopy (LIBS) and discriminant function analysis (DFA). To achieve this goal, four normal standard samples with different concentrations of cholesterol and one pathological sample as a target, all from human blood serum, are prepared. Initially, the range

It has been known for some time that Bessel–Gaussian beams and their associated families self-heal after encountering obstacles. Recently, it has been shown theoretically and experimentally that radial mode Laguerre–Gaussian (LG) beams would likewise self-heal. In this work, we show that the self-healing occurs after opaque disks but not after circular apertures. We put forward arguments to explain

This manuscript presents the development of a two-color laser-absorption-spectroscopy (LAS) sensor capable of providing calibration-free measurements of temperature and H\(_2\)O at 1 MHz in particle-laden combustion environments. This sensor employs scanned-wavelength-modulation spectroscopy with first-harmonic-normalized second-harmonic detection (scanned-WMS-2f/1f) with two distributed-feedback (DFB)

We report a novel approach to the design and implementation of a tunable cavity on an optical nanofiber (ONF). The key point is to create a composite photonic crystal cavity (CPCC), by combining an ONF and a diverged period defect mode grating. Using numerical simulations we design the CPCC with low scattering loss while tuning the cavity resonance wavelength of ±10 nm around the designed wavelength

In this paper, we study the possible parametric down-conversion processes in a type II phase-matched, Lithium Niobate ridge waveguide, designed to generate photon pairs in the telecommunication range. A quantum analysis of spontaneous parametric down-conversion (SPDC), first, with a pulsed Gaussian pump beam and second, with a pulsed, spatially anti-symmetric Hermite-Gaussian HG (1,0) pump beam predict

We report the design of ultra-broadband, highly reflective all-dielectric reflectors covering the entire visible regime based on two cascaded subwavelength high-index-contrast gratings (HCGs). We find that the spectral distance between the two gratings’ reflective bandwidths, which should be appropriately designed in order to extend the overall bandwidth for high reflectivity, is analogous to the well-known

A novel high-power fiber laser oscillator employing a saddle-shaped core ytterbium-doped fiber (SSCYDF) is proposed and demonstrated experimentally. The SSCYDF is designed and fabricated with a long-tapering core (diameter of ~ 30 µm at both ends and ~ 23 µm in the middle) and a constant inner cladding (diameter of ~ 400 µm) in longitudinal dimension. On the one hand, the small core section of the

The accuracy of tropospheric temperature measurements with pure rotational Raman (PRR) lidars is affected by the collisional broadening of N2 and O2 PRR lines. In this paper, we intercompare nine calibration functions (CFs) in the traditional PRR lidar technique via simulation. Taking into account the PRR line broadening, the simulation is performed for five sets of spectral filters (SFs) with different

We demonstrate an improved concept for nearly bandwidth-limited nonlinear pulse compression down to the few-cycle regime in a fiber chain with alternating sign of dispersion. Whereas the normally dispersive fiber segments generate bandwidth via self-phase modulation, the anomalously dispersive fiber segments recompress the broadened spectral bandwidth by an appropriate amount of group velocity dispersion

As the cap rock for oil and natural gas traps, tight shale with small interstitial spaces and invisible beddings were found to have large reserves and rich mining value. Precise identification of feature anisotropy in tight shale is of significance in the development of petroleum reservoirs. Here in this work, we demonstrate an application of a 532-nm laser to measure the lateral photovoltaic (LPV)

A double-clad single-mode tellurite optical fiber (DC-SMTOF) with a loss of 0.5 dB/m @1545.1 nm was fabricated based on the TeO2–ZnO–Li2O–Bi2O3 (TZLB) material. During the fiber drawing process, a low level of residual birefringence was produced, which gave a chance for the investigation of the polarization modulation instability (PMI). With a nanosecond laser operated at 1545.1 nm as the pump source

A quantum cascade laser-based infrared spectrometer equipped with a multipass cell has been used to perform sensitive infrared spectroscopy of isoprene at part per billion (ppbv) concentration levels. The instrument was used to measure the absorption of the strong Q-branch of the ν26 vibrational mode of isoprene near 992 cm−1 to determine isoprene concentrations in gas-phase samples. The response of

Energy and spectral–temporal characteristics of lasers on heavily doped single crystals Fe:ZnSe are studied. With the cavity formed by faces of the crystal at a bivalent iron concentration of 2.8 × 1019 cm−3, the slope and total laser efficiencies with respect to the absorbed energy were 53% and ≈ 42%, respectively. Laser spectra with the cavity free of air and elements capable of forming Fabry–Perot

Tomographic measurements of ammonia concentration in diesel engine exhaust dosed with diesel exhaust fluid are demonstrated through spatial scanning of a 10.4 μm quantum cascade laser beam. Optical access through the exhaust pipe was facilitated by a polyimide film. The laser beam was translated in 0.5 cm increments and rotated in 6 degree angular increments, resulting in 2130 unique laser beam positions

Titanium dioxide nanoparticles have been synthesized by the chemical co-precipitation technique and then they have been coated with zinc oxide shell layers using a refluxing method to form TiO2/ZnO core/shell nanoheterojunctions. The physicochemical properties of as-synthesized core/shell nanoheterojunctions have been examined using X-ray diffraction (XRD), Fourier transfer infra-red spectroscopy (FT-IR)

A defective molybdenum oxide (MoO3−x) prepared by a hydrothermal and defect engineering approach was spin-coated on the quartz glass and implemented as saturable absorber (SA). The experiment evidenced that MoO3−x based SA can function as an efficient nanosecond pulse generator, servicing Nd3+, Er3+, Tm3+ doped lasers emission at 1.06 1.64 and 1.94 µm. And the shortest pulse duration of 396 ns, 275 ns

We have investigated the difference between adiabatic and isothermal compression of liquids by an impacting weight, as observed in the resulting change to the index of refraction. The liquids examined were sebacate, glycerol, and water. For practical reasons, sebacate is best suited for the use of a drop-weight apparatus as a metrologically traceable calibration facility for dynamic pressure. We find

We study a method for mass-selective removal of ions from a Paul trap by parametric excitation. This can be achieved by applying an oscillating electric quadrupole field at twice the secular frequency \(\omega _{\text {sec}}\) using pairs of opposing electrodes. While excitation near the resonance with the secular frequency \(\omega _{\text {sec}}\) only leads to a linear increase of the amplitude

We report a tunable single-longitudinal-mode laser based on a wedged Nd:YVO4 gain medium and a YVO4 wave-plate. By taking advantage of the natural birefringence of YVO4 and adopting different cutting methods, a wedged Nd:YVO4 crystal acts as an ideal polarizer by the alignment sensitivity of the optical resonator, and a YVO4 crystal is used as a wave-plate by adjusting the temperature. A theoretical

In this paper, we show that graphene-coated nanowire integrated with a semi-elliptical dielectric substrate could enable excellent subwavelength transmission performance in the mid-infrared range. The fundamental graphene plasmon mode behaviors on the thickness of silica layer, ratio of long- to short-axis of the ellipse, nanowire radius, and chemical potential of graphene are revealed in detail. By

Semiconductors are considered as promising materials for the fabrication of photo-thermo sensors with high sensitivity. Therefore, here we propose to synthesize of amorphous 2D single-layered structures with high thermo-photosensitivity by using photons generated by a KrF* laser radiation (λ = 248 nm, τFWHM ≤ 25 ns) in the reaction of copper (Cu) atoms with methane (CH4) molecules by reactive pulsed

We report on the design and modeling of vertical-cavity surface-emitting laser (VCSEL) integrated in the lateral direction with a cascade of multiple passive cavities. The scheme is proposed to increase the bandwidth of the VCSEL in the mm-waveband to generate ultra-high-frequency oscillations with low-frequency chirp. The model treats the transverse feedback induced by the cascaded transverse coupled

This paper presents new structures for OR, NOT, and XOR logic gates based on a two-dimensional photonic crystal. The proposed structures are quite linear and have the same basic structure for all three gates. Isolation between input ports is one of the features that is given special attention in this study. The proposed designs reduce the leakage signal from an input port to another input port to less

Transverse mode-locking in an end-pumped solid state laser by amplitude modulation with an acousto-optic modulator was investigated. Using the stochastic parallel gradient descent algorithm the modal power coefficients and the modal phases of the transverse mode-locked (TML) laser beam were reconstructed from the measured spatial and spatio-temporal intensity distributions, respectively. The distribution

Simultaneous dual-plane stereoscopic particle-imaging velocimetry (DS-PIV) and hydroxyl planar laser-induced fluorescence (OH-PLIF) was performed at 10 kHz repetition rate in a highly turbulent swirling jet flame. The burst-mode laser system provides sufficient 532-nm dual-pulse energy enabling high-speed large-area dual-plane stereo-PIV measurement. The scattered light from the two planes was separated

Processing method plays an important role in accelerating imaging process in ghost imaging. In this study, we propose a processing method with the Hadamard matrix and a deep neural network called ghost imaging hadamard neural network (GIHNN). We focus on how to break through the bottleneck of image reconstruction time, and GIHNN can identify an object before the imaging process. Our research reveals

Recent advances in wavefront shaping, i.e., wavefront modulated by a spatial light modulator, have opened hopeful venues to focus light through scattering media in particular and unparalleled ways, by means of codifying the values of pixels of the modulator. The transmission matrix approach is one of the most exciting recent advances to obtain optimal phase distributions, due to the consent of enabling

In the paper, based on the linear Schrödinger equation, we analytically investigate the effect of initial chirp on the dynamics of the optical beam in a medium with the parabolic potential. For the linear chirp, the results show that the linear chirp of beam can induce a periodically oscillating behavior, where the oscillating amplitude is proportional to the linear chirp parameter, and the beam’s

Multi-resolution imaging is one of the key means to obtain the target scene information. The Hadamard matrix, which is orthogonal, is an important modulation matrix for single-pixel imaging. In particular, it can provide a good means for multi-resolution imaging. However, as far as we know, studies of high-efficiency multi-resolution single-pixel imaging are rare in the literature. In view of the practical

Dynamic light scattering (DLS) is a widely used, non-invasive and in-situ method for particle size measurement. However, the precision of the measurement results is still under discussion. Theoretically, the apparent hydrodynamic diameter measured by DLS varies with scattering angle due to Mie scattering as well as long-distance interaction between particles. In this paper, a multiple-angle dynamic

We report on the characterization of the angular-dependent emission of single-photon emitters based on single nitrogen-vacancy (NV-) centers in nanodiamond at room temperature. A theoretical model for the calculation of the angular emission patterns of such an NV-center at a dielectric interface will be presented. For the first time, the orientation of the NV-centers in nanodiamond was determined from

The seawater salinity and temperature of an ocean are key parameters required for environmental evaluation, with Raman and Brillouin scattering techniques offering a potentially accurate approach. A method for Brillouin scattering spectrum measurement based on a double-edge technique is proposed, and a retrieval model for simultaneously acquiring Brillouin shifts and linewidths is built. The accuracy

We present directly oscillator-driven self-compression inside an all-bulk Herriott-type multi-pass cell in the near-infrared spectral range. By utilizing precise dispersion management of the multi-pass cell mirrors, we achieve pulse compression from 300 fs down to 31 fs at 11 µJ pulse energy and 119 W average power with a total efficiency exceeding 85%. This corresponds to an increase in peak power

Recently, we reported on the development of a series of Dy-doped organic molecular crystals (with analogous material properties to energetic organic molecular crystals) for use as two-color thermometry phosphors in thermometric imaging of heterogeneous materials under shock compression. In this study, we demonstrate thermometric imaging of one of these phosphors—Dy:Y(acac)\(_3\)(DPEPO)—under pulsed