Acetylene black is a special type of carbon black, obtained from the thermal decomposition of acetylene. Acetylene flames enable the investigation of the soot optical properties. A reliable knowledge of the optical properties of acetylene soot is necessary for interpreting the optical measurements in flames and the development of acetylene black applications in industry. However, a wide variation in

Two-dimensional temperature measurements using filtered Rayleigh scattering (FRS) were performed in confined CH4/air swirl flames at atmospheric pressure. The investigated burner has a combustion chamber consisted of four quartz windows. The combustion chamber is 160 mm high with a square section of 50 × 50 mm2. Measurements were challenging due to the strong interference from the incident laser impinging

This work describes the diagnostic implementation and image processing methods to quantitatively measure diesel spray mixing injected into a high-pressure, high-temperature environment. We used a high-repetition-rate pulse-burst laser developed in-house, a high-speed CMOS camera, and optimized the optical configuration to capture Rayleigh scattering images of the vaporized fuel jets inside a constant

We developed a high-power dual-wavelength green pulsed laser that generates 528-nm and 535-nm laser pulses which overlap completely in time and space. Two single-frequency seed lasers of 1056 nm and 1070 nm are combined and amplified to 140 W through a series of ytterbium-doped fiber amplifiers including a rod-type fiber amplifier, and the amplified laser pulses of two wavelengths are frequency-doubled

Intra-cavity pumped Ho laser basing on the biaxial YAP host is investigated here for a direct LD pumped compact polarized 2.1 μm laser at room temperature, where the a-cut and b-cut Tm:YAP and Ho:YAP crystals were applied and placed with the same crystallographic orientation. The maximum output power of 2.47 W at 2118 nm was obtained for the b-cut Ho:YAP laser with a slope efficiency of 15.1%, which

The use of laser beams made up of ultrafast pulses for the processing of materials can be bothered by the consequences of optical Kerr effect (OKE) cumulated by the propagation through optical devices (windows, laser crystal, prisms, lenses, …). The latter are mainly a reduction of the intensity in the focal plane accompanied by a distortion of the temporal and spatial pulse shape. We present a comparative

A Tm3+:Y2O3 ceramic laser with the L-shaped cavity in-band pumped by a fiber laser at 1670 nm was studied in the CW and passively Q-switched regimes. The CW laser was tunable in the range between 2046 and 2054 nm. The output power reached up to 4.9 W and the average slope efficiency was 75% in the high-quality single-transverse-mode beam The highest CW output power in the multi-transverse-mode beam

The period (\(\wedge \)) of nanograting in sapphire varied from 320 to 398 nm with increasing the laser fluence, which is similar to the change trend of period of the near-subwavelength ripples previously observed on the material surface (\(0.4<\wedge / \lambda <1\)) (Huang et al. in ACS Nano 3:4062, 2009). The result shows that the interference of the incident laser with the plasma could take place

The conversion of transverse mode-locked (TML) laser beams from a Hermite-Gaussian (HG) to a Laguerre-Gaussian (LG) mode set using a cylindrical lens mode converter was demonstrated experimentally. By changing the spatial symmetry of the beams new spatio-temporal dynamics for TML lasers were enabled. In particular, the fast linear motion of an oscillating laser spot, generated by a TML laser based

Experimental and simulation studies show that a hexagonal array of polystyrene particles on a gold substrate, capped with gold semi-shells, results in increased optical confinement of the resonance modes in comparison with those for arrays without metallic substrate or capping. Well-ordered arrays of polystyrene beads were fabricated by convective deposition, a solution-based self-assembly process

In this study, we have designed and simulated a photonic crystal (PhC) nonlinear AND logic gate. First, a suitable photonic crystal ring resonator (PhCRR) structure is designed and simulated that can be used for obtaining the switching power intensity after applying the nonlinear Kerr effect. In this structure, GaAs dielectric rods have been used in the air. The plane wave expansion (PWE) method is

We experimentally characterize the positions of the diffraction maxima of a phase grating on a screen, for laser light at oblique incidence (so-called off-plane diffraction or conical diffraction). We discuss the general case of off-plane diffraction geometries and derive basic equations for the positions of the diffraction maxima, in particular for their angular dependence. In contrast to previously

A novel tunable terahertz metamaterials polarization converter (PC) is presented in this paper, whose operating band can be extended by the innovative band splicing technology (combine different PCs with different bands to make the bands splice together) and adjusted into a broadband absorber via adjusting the temperature. Four different units are combined to form a supercell and the phases can be

Genetic analysis is considered to be the ultimate diagnostic approach in many fields, e.g., in medicine for disease detection, in agricultural technology for food and feed authentication, in forensics, to name a few. Consequently, great interest is growing in developing sensitive and reliable analytical tools (biosensors) to identify whole DNA sequences, oligonucleotide fragments, or single-nucleotide

In this work the fabrication and characterization of As2S3 and erbium-doped As2S3 layers on Er:Ti:LiNbO3 channel waveguide amplifiers are reported and compared with Er:Ti:LiNbO3 channel amplifier for the first time to the author’s knowledge. We have first characterized a typical Er:Ti:LiNbO3 waveguide amplifier of 2.6 cm length and measured a small signal net gain of 2.5 dB for TM mode under 1470 nm

An efficient but simple scheme of an axicon-based resonator for tuning the spatial mode of high-power and high-order Bessel–Gaussian beams is proposed. This scheme is extended for two types of high-power lasers: continuous wave (CW) and Q-switched lasers. More importantly, the right axicon apex angle, the resonator optical length and the internal aperture diameter and its place inside the resonator

For stationary light fields, the degree of polarization (DOP) of light relates to the maximum correlation between two arbitrarily decomposed orthogonal electric field components at a space–time point. We generalize this understanding theoretically by showing a physically insightful connection between DOP and the two-time degree of coherence of electromagnetic fields. Further, by using a variable path

Er3+ doped tellurite glasses have been the subject of current research for potential applications in photonics. When compared with other glasses, these materials exhibit some valuable properties in the field of optical fiber amplification or laser radiation generation, such as a high refractive index, a broad photoluminescence band around 1550 nm, high chemical and thermal stability, high infrared

The characteristic parameters as well as self-generated electric and magnetic fields of Nd:YAG laser (532 nm, 10 ns) ablated Al plasma have been measured by employing Langmuir, electric and magnetic probes, respectively. Plasma parameters such as electron temperature (\({T}_{e}\)) and electron number density (\({n}_{e}\)) as well as SGEMFs of Al plasma are measured as a function of laser irradiance

A fiber optic temperature sensor consisting of two cascaded high birefringence fiber loop mirrors (Hi-Bi FLMs) was proposed and experimentally demonstrated to enhance the temperature sensitivity and resolution by Vernier effect. The FSRs for the two Hi-Bi FLMs are designed to be slightly different to generate the Vernier effect. The working principle for the proposed sensor is analogous to Vernier-scale

The diagnosis of cyst structures that can be seen in almost every part of the body can be made using various medical imaging methods recently. Although the used methods and devices provide convenience in diagnosis and treatment, sometimes they can not detect early-stage cyst structures without showing any symptoms. In this study, the cystic structures with different size and formation in phantoms which

We report on the formation of various intensity pattern types in detuned Fourier domain mode-locked (FDML) lasers and identify the corresponding operating conditions. Such patterns are a result of the complex laser dynamics and serve as an ideal tool for the study of the underlying physical processes as well as for model verification. By numerical simulation we deduce that the formation of patterns

Fluorescence spectra and lifetimes of anisole and toluene vapor in nitrogen have been measured at conditions below ambient (257–293 K and 100–2000 mbar) upon excitation with 266-nm laser light to expand the applicable range of anisole and toluene laser-induced fluorescence (LIF) for conditions below room temperature that occur in expanding flows and cases with strong evaporative cooling. Anisole fluorescence

In this paper, a quasiparticle concept was proposed to understand the branched flow of light phenomenon. Combined with the geometrical optical theory, we successfully established a model to simulate the branched flow of light with this novel perspective. Our model owns an intuitive physics picture, without losing generality. Moreover, we demonstrated that a special structure with the fixed position

Laser-plasma accelerators can produce ultra-short electron bunches in the femtosecond to picosecond duration range, resulting in very high peak dose rates in comparison with clinical accelerators. This unique characteristic motivates their possible application to radiation biology studies to elucidate the effect of high peak dose rates and peculiar temporal structures on the biological response of

We report on experimental observation of four phase-locked bound soliton formation in a SESAM mode-locked \(\hbox {Cr}^{2+}\):ZnSe laser with an output power of 20 mW, a temporal pulse-to-pulse separation of 18.2 ps and single pulse duration of 1.4 ps. We demonstrate that birefringence can be used as an efficient mechanism to achieve bound state generation in solid-state lasers as an alternative method

We present an overview of recent results on optical coherence tomography with the use of extreme ultraviolet and soft X-ray radiation (XCT). XCT is a cross-sectional imaging method that has emerged as a derivative of optical coherence tomography (OCT). In contrast to OCT, which typically uses near-infrared light, XCT utilizes broad bandwidth extreme ultraviolet (XUV) and soft X-ray (SXR) radiation

We present a low-cost multimode diode pumped passively Q-switched Cr:LiCAF laser operating near 800 nm. AlGaAs-based saturable Bragg reflectors (SBRs) were used for passive Q-switching. The system is experimentally characterized in detail using four different output couplers and two SBRs with different modulation depths. Pulse widths in the 1.5–4 µs range at repetition rates between 18 and 40 kHz were

Persistent time-delayed luminescence was observed in bulk polymer Polyamide-6 (nylon 6) samples at room temperature. Using X-ray 2Θ-diagnostics we have separated two crystalline forms of the material which exhibit serious differences in their time-delayed luminescence properties. Whilst for the α-form the afterglow temperature threshold is at the range of 100 °C, the γ-form samples require cooling

Laser-produced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different target positions relative to the waist region of laser focusing are studied using fast imaging and optical emission spectroscopy (OES). The laser energy of the two laser pulses is both maintained at around 18 mJ (i.e. the total energy is 36 mJ). The inter-pulse delay is kept at 250 ns. Ten spot sizes

In the present work, laser-induced plasma (LIP) of Mo is studied using both time and space resolved laser-induced breakdown spectroscopy (LIBS) in air as a function of incident laser energy. For this a second harmonic Q-switched Nd:YAG laser having pulse width of 7 ns and repetition rate of 1 Hz is used. The Boltzmann plot method is employed to estimate the plasma temperature of LIP using MoI and MoII

The two-dimensional multi-angle light scattering (2D-MALS) technique has been extended for single-shot size measurements of soot aggregates in flames. Six cameras are used for instantaneous acquisition of the elastic scattering from the aggregates at different directions between 10 to 90\(^\circ\) of a laser light sheet. Two diluted ethylene (50 and 60% by volume of \(\hbox {C}_2\hbox {H}_4\) fuel

The device of multi-pass-cell (MPC) could broaden the spectra of ultrafast laser pulses based on the self-phase-modulation (SPM) effect, which is composed of two concave mirrors and nonlinear mediums. In this paper, the pulse duration of 172 fs is compressed from a 11.3 ps Nd: YVO4 regenerative amplifier at the repetition rate of 1 kHz by using two stages of MPC systems. The pulse duration is shortened

We present detailed experimental results with cryogenic Yb:YLF gain media in rod-geometry. We have comparatively investigated continuous-wave (cw) lasing and regenerative amplification performance under different experimental conditions. In the cw lasing experiments effect of crystal doping, cw laser cavity geometry and pump wavelength on lasing performance were explored. Regenerative amplification

As a novel computational imaging (CI) method, single pixel imaging (SPI) can obtain the spatial information of the target object with only a single-pixel detector, especially the SPI with Fourier basis has higher imaging efficiency and quality. However, Fourier single-pixel imaging (FSI) will still be affected in atmospheric turbulence, imaging will be unstable, and image quality will decrease. This

This study investigates the thermal performance of cryogenic micro-pin fin coolers for high-power laser diode (LD) bars. An open-loop liquid nitrogen cooling system, used to operate LD bars at cryogenic temperatures, is developed and characterized. The comparison study demonstrates that the total thermal resistance value of the micro-pin fin cooler, ranging from 0.03 to 0.04 °C/W, is only 1/3 of that

The splash created by intense laser pulse impact onto a liquid tin layer is studied experimentally using time-delayed stroboscopic shadowgraphy. An 8-ns infrared (1064 nm) laser pulse is focused onto a deep liquid tin pool. Various laser spot sizes (70, 120, and 130 \(\upmu\)m in diameter) and various laser pulse energies (ranging 2.5–30 mJ) are used, resulting in laser fluences of \(\sim\) 10–1000 J/cm\(^2\)

For the first time, we studied the change in a short-wavelength cutoff of a mid-IR pulse spectrum with an increase in a nonlinear optical interaction length in calcium fluoride. We investigate a transformation of an anti-Stokes wing in a pulse spectrum during light bullet formation under anomalous group velocity dispersion. An experimental scheme allowing a variation of a pulse propagation length in

This work proposes a method for aligning a femtosecond multi-petawatt coherent beam combining system under quasi-static conditions. This method does not depend on the details of the laser system, and only exploits the information of the fluence distribution in the far field as the feedback for the control of a deformable mirror and a reflective mirror in each optical path to optimize the system in

Atomic comagnetometers, which measure the spin precession frequencies of overlapped species simultaneously, are widely applied to search for exotic spin-dependent interactions. Here we propose and implement an all-optical single-species Cs atomic comagnetometer based on the optical free induction decay (FID) signal of Cs atoms in hyperfine levels \(F_{g}\) = 3 and 4 within the same atomic ensemble

Image encryption converts a meaningful image into some random arrangement of pixel intensities. That means, the intelligible property of an image is destroyed. Taking into consideration excessively large time and space complexity required by the image encryption algorithm using multiple chaotic systems, this paper proposes an image encryption method in which employs three chaotic sequence to achieve

A THz-pulse-driven compact, < 150 mm in total length, two-stage electron accelerator setup was designed. It uses 2 × 2 pairs of nearly counter-propagating focused THz pulses. The effects of the initial bunch charge and the propagation direction of the THz pulses on the energy of the accelerated electrons were investigated by numerical simulations. Generation of 8 fC electron bunches with up to 340 keV

The development of real-time and on-line quantitative composition analysis is desired for the products quality improvement in the metal producing and processing industries. Accuracy is still a challenge for classical calibration-free laser-induced breakdown spectroscopic (CF-LIBS) quantitative analysis due to the influence of the inaccurate plasma temperature calculations, uncertainties associated

Soot radiation-based thermometry is a popular approach for flame temperature diagnostics. However, it usually suffers from flame temperature information lost in the regions of soot absent or less significant area. The originality of the present work lies in the development of a two-step Multi-Layer Perceptron (MLP) neural network method to assist soot radiation-based thermometry for flame temperature

A presentation based on the helical long-period grating (H-LPFG) affected by the change of temperature and twist has been demonstrated. There are two resonant peaks near 1451 nm (resonant peak 1) and 1519 nm (resonant peak 2) when the pitch length is about 757 μm. The resonant peak 1 is caused by second-order diffraction coupling between the fundamental mode and the LP110 cladding mode, and the resonant

Machine learning (ML) methods are implemented to classify rotational absorption spectra for gas-phase compounds in the THz region, specifically 220–330 GHz where experimental data is available. Eight ML methods were trained in both standard and one-versus-rest (OVR) implementations using simulated absorption spectra for 12 volatile organic compounds and halogenated hydrocarbons of interest in industrial

The red emission of Eu3+ ions embedded in glasses containing copper with distinct plasmonic properties is reported. Either a photoluminescence (PL) enhancement or quenching is manifested depending on whether the nanocomposite is dichroic (scatters red but transmits blue) or not (ruby-colored). In addition, Eu3+ emission in the dichroic glass is indicated to be either enhanced or quenched depending

In this study, a laser ultrasonic technology (LUT) was employed for seismic physical model (SPM) imaging. To promote an efficient light-to-ultrasonic-wave conversion, a functionalised Au film was used as a medium because of its stronger photoacoustic (PA) effect. Numerical analysis and experiments were performed to characterise the entire SPM imaging process, including the generation of PA signals

We propose a transmissive circular polarization converter with reduced thickness and high performance. The proposed device is composed of a three-layer metasurface spaced by two dielectric plates. The top and bottom layers are metasurfaces formed by meander lines, and the middle metasurface is a modified fishnet structure etched periodically with gaps along the x-direction. By employing these periodic

A detailed investigation is performed to obtain optimized optical performance of polar III-nitride single quantum well (SQW) semiconductor lasers by band engineering through symmetric and asymmetric tuning of device parameters. Electronic, optical, and threshold characteristics are calculated to analyze the effects of band engineering on device performance. Here, the InN-In0.25Ga0.75 N SQW structure

Lithium Niobate (LiNbO3; LN) nanoparticles were dispersed into a polymer matrix, poly(methyl methacrylate) (PMMA) to prepare an organic–inorganic hybrid LN/PMMA nanocomposites. When no electric field was applied during dispersion, the polar LN nanoparticles remain randomly oriented in the PMMA and unpoled nanocomposite is obtained. In this work, poled LN/PMMA nanocomposites were prepared by applying

Allowing for the simultaneous determination of the photocarriers drift mobilities and their small-signal recombination lifetime, the Moving photocarrier Grating Technique (MGT) is a useful characterization tool for photoconductive semiconductors. This technique is based on measuring the steady-state direct current induced by an interference pattern (IP) moving at a constant velocity between two coplanar

The interaction of linearly polarized light with self-assembled photonic crystals (opals) grown from polymeric colloids is studied. The experimental work is carried out on opals with and without dye molecules. These active and passive opals influence the polarization state of transmitted light very differently and the role of photonic stop band is evident. The active opals, when excited within the

A novel configuration of a low-aberration single diffraction grating stretcher for femtosecond chirped-pulse amplification lasers is proposed. The stretcher configuration employs two identical concave parabolic mirrors separated by a distance equal to their focal length. Using the numerical ray-tracing approach, the proposed design is compared with conventional Martinez and Öffner configurations in

A binary phase-only modulation technique was proposed to focus and scan light through a multimode fiber (MMF) based on spatial light modulator (SLM). For the same number of modulation modes, the number of iterations using this method is only 1/256 of that using phase-only iterative optimization or 1/3 of that using phase-only computation optimization, and the modulation time is at least one to two

The harmonic generation efficiency of a large aperture KDP (KH2PO4) crystal that is used in the Final Optics Assembly of high-energy solid-state lasers is one of the key points to achieve inertial confinement fusion. The variations in the detuning angle of a KDP crystal are achieved by interferometer and calculation. The harmonic generation efficiency is calculated using variations in the detuning

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