Double Laser Research Articles

Simulation and experimental study on double staggered-axis air-assisted water jet-guided laser film cooling hole machining

Air film cooling structure is an important factor to improve the cooling performance of aero-engine turbine blades. In order to realize high-efficiency and high-quality machining of turbine blade air film holes, a new method of water jet-guided laser (WJGL) machining based on double staggered-axis auxiliary gases is proposed. On the basis of the currently commonly used helium coaxial auxiliary jet, an external staggered axis argon auxiliary jet is added. The external staggered-axis gas jet can blow away the exiting liquid close to the water jet while improving the gas protection range. The simulation results verify the blowing away effect of the outer staggered-axis assisted gas jet on the outwardly discharged liquid. The experimental results show that, in terms of processing efficiency, the double staggered-axis gas-assisted WJGL technology improves 35.1 % and 15.6 % higher compared with the single-axis gas-assisted and double coaxial gas-assisted methods, respectively. In terms of processing quality, the double staggered-axis gas-assisted WJGL technology processes the inner wall surface of the micro-hole with less taper and roughness, and the processing consistency is better. The double staggered-axis gas-assisted WJGL technology with a laser power of 40 W and an external staggered-axis angle of 35° was applied to process holes with a depth of 4 mm and a diameter of 0.8 mm in a nickel-based high-temperature alloy. The average penetration time of the holes was 152 s, the wall roughness Ra was less than 0.4 μm, and the thickness of the heat-affected zone was less than 1 μm.

Characterizing the as-built surface topography of Inconel 718 specimens as a function of laser powder bed fusion process parameters

Purpose The ability to use laser powder bed fusion (LPBF) to print parts with tailored surface topography could reduce the need for costly post-processing. However, characterizing the as-built surface topography as a function of process parameters is crucial to establishing linkages between process parameters and surface topography and is currently not well understood. The purpose of this study is to measure the effect of different LPBF process parameters on the as-built surface topography of Inconel 718 parts. Design/methodology/approach Inconel 718 truncheon specimens with different process parameters, including single- and double contour laser pass, laser power, laser scan speed, build orientation and characterize their as-built surface topography using deterministic and areal surface topography parameters are printed. The effect of both individual process parameters, as well as their interactions, on the as-built surface topography are evaluated and linked to the underlying physics, informed by surface topography data. Findings Deterministic surface topography parameters are more suitable than areal surface topography parameters to characterize the distinct features of the as-built surfaces that result from LPBF. The as-built surface topography is strongly dependent on the built orientation and is dominated by the staircase effect for shallow orientations and partially fused metal powder particles for steep orientations. Laser power and laser scan speed have a combined effect on the as-built surface topography, even when maintaining constant laser energy density. Originality/value This work addresses two knowledge gaps. (i) It introduces deterministic instead of areal surface topography parameters to unambiguously characterize the as-built LPBF surfaces. (ii) It provides a methodical study of the as-built surface topography as a function of individual LPBF process parameters and their interaction effects.

The spatio-temporal evolution of shock wave pressure induced by laser: Effects of laser parameters and confinement layer

The spatio-temporal distribution of the shock wave pressure on the surface of the target is the key to the performance of laser shock processing (LSP), which is mainly determined by the laser parameters and the confinement layer. The two-dimensional kinetic simulations of the expansion process of the shock wave induced by irradiation of an aluminum target with nanosecond laser pulses are performed. It is found that by controlling the gap between the rigid confinement layer and the aluminum target, and the interval time between the double pulse laser pulses, multiple peaks appear on the shock wave pressure-time curve of the aluminum target surface, and the value and interval time of each peak will change.

Boosting pulse characterization precision for Ho: YAP double pulse laser with back propagation neural network.

The precise energy and temporal control advantages of the 2 µm double-pulse laser have diverse applications in laser processing, biomedicine, and communications. The Ho: YAP Q-switched double pulse laser, a complex system, demands comprehensive theoretical analysis and precise experimental operations, especially when managing pulse overlap and ensuring output stability. Traditional design methods, time-consuming and labor-intensive, pose challenges in error elimination and susceptibility to environmental and device instabilities. This paper focuses on regulating the design and performance of the Ho: YAP Q-switched double-pulse laser. Critical developmental and optimization challenges are addressed by utilizing a back propagation neural network to forecast the nonlinear propagation of the laser while affirming the feasibility of bypassing intricate numerical solution models. This strategy streamlines experimental trials, ensuring reliable predictions of laser output characteristics and laying the foundation for forecasting more intricate laser systems in the future.

Double laser two-step process for creating interconnected frame microstructures' superhydrophobic surface with dual scales

Superhydrophobic surfaces have garnered significant attention for their unique wettability and extensive applications across various critical fields. In this paper, a two-step laser processing technique, involving infrared nanosecond laser patterning and ultraviolet picosecond laser surface modification, was employed to fabricate interconnected frame surfaces with dual-scale microstructures on Ti6Al4V substrates. After that, the microstructure surface was chemically modified with 1H,1H,2H,2H-perfluorodecyl trimethoxy-silane to achieve a superhydrophobic surface. An L32 (47) orthogonal experiment was used to analyze the effect of seven main factors (including the structure size, scanning velocity and the fluence, number of scans of infrared nanosecond laser and ultraviolet picosecond laser) on the wettability of the interconnected frame microstructures surface. After optimization, the surface strongly corresponded with the Cassie-Baxter model and demonstrated a water contact angle of 153.22±1.64° and roll-off angle of 4.43±1.70°. The experiments demonstrated that the optimized surface possesses excellent mechanical stability and corrosion resistance. Additionally, the optimized surface exhibits anti-adhesion, effective self-cleaning, and anti-fouling properties, which hold promise for addressing issues of liquid adhesion and dust pollution in industrial machinery.

Design of tensile-strained GeSn/SiGeSn structure for low threshold mid-infrared laser application

The plasticity of GeSn alloy energy band has promoted the development of silicon-based photoelectric integration and optical interconnection. A tensile-strained GeSn/SiGeSn double heterostructure laser wrapped with Si3N4 stress liner is designed and characterized theoretically. The triaxial tensile strain is introduced into the GeSn/SiGeSn heterostructure laser by the Si3N4 linear stressor. The lower threshold current density and higher optical gain of the GeSn/SiGeSn laser can be achieved by tuning the band structure and carrier distribution in the active region with tensile strain and Sn compositions. Compared with the relaxed device, the value of ne ,Γ/ne ,total for the Ge0.90Sn0.10/Si0.315Ge0.499Sn0.186 heterostructure laser wrapped with 300 nm Si3N4 linear stressor is increased to 30.6% at n e,total of 1018 cm−3, the laser λ can be extended to 3.44 μm, and the J th is reduced from 206 to 59 A/cm2.

Diarylethene derivative photoionization control via two-color two-laser optical manipulation in the presence of cyclodextrins

In this study, the photodynamics of 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DE) was investigated in the presence of α-, β- and γ-cyclodextrin (CD) inclusion complexes and under the influence of one- and two-laser excitations. Thus, this study aimed to elucidate the ionization quantum yield of DE and how it is affected by the type of CD and laser configuration. Specifically, DE/CD was flash photolyzed using a single laser (355 nm) or a double laser (355 nm and 532 nm) and observed at a wavelength of 720 nm to examine the transient absorption of hydrated electrons. The ionization efficiency with the two lasers was found to exceed that with the single laser. This suggests the existence of a two-step process involving S0→S1 and S1→Sn singlet transitions in the two-photon ionization (TPI) of DE. Furthermore, when the ring-closing isomer of DE was initiated via laser irradiation at 532 nm, the photoionization efficiency increased, especially in the presence of γ-CD. This implies that the 532-nm irradiation, which is not directly involved in TPI, contributed to promoting the TPI of DE, thus increasing its photo-steady state (saturation). Thus, the possibility of using CD-containing lasers to control photochemical reactions with photo-steady state processes was demonstrated. This investigation contributes to a broader understanding of the potential applications and underlying mechanisms of photochromic materials influenced by multi-laser interactions.

Spectroscopic assessment and quantitative analysis of the trace element composition of vegetable additives to meat products

In this scientific work, using the method of laser-induced breakdown spectroscopy (LIBS), the spectra of beef samples and impurities in meat products, namely, banana, pineapple, kiwi, bergamot, poria coconut, Chinese angelica, chicken blood vine, were measured by using developed experimental devices. The purpose of the research was to evaluate the qualitative characteristics of additives to meat semi-finished products for the potential formation of the desired properties of the products due to the analysis of the received spectrograms of trace elements of the samples when applying the LIBS method, quantitative analysis for processing the received information. The determined values of the electron temperature of the plasma, the electron density of the used raw material samples, and the assessment of the local heat balance were used as evaluation criteria. When processing the obtained data, the characteristics of the laser-induced plasma surface of the presented samples were analyzed; the electron temperature and electron density were determined, and a quantitative analysis of trace elements was carried out. LIBS technology allows rapid real-time monitoring and qualitative analysis of trace elements online and over long distances. During the research, it turned out that quantitative analysis requires further study and optimisation of experimental conditions, such as pre-treatment of samples. These conditions optimise defocusing, double laser pulse, and sample temperature, which increases the signal/noise ratio of all spectral lines. The combination of fluorescence spectroscopy and Raman technology enables higher detection sensitivity and better molecule control, creating a quantitative analysis method model that can reduce matrix effects and overcome the self-absorption effect. Among the difficulties of using LIBS technology, several elements can be noted online simultaneously, compared to Raman. The combination of spectroscopy and fluorescence spectroscopy can obtain more comprehensive information about the composition of materials, which can become a potential platform for monitoring trace elements in food products.

Research and development of double layer P-doped laser induced graphene thin film electrode for flexible micro-supercapacitor applications

Laser-induced graphene (LIG) has garnered significant attention for its cost-effectiveness and high efficiency in fabricating flexible micro-energy storage devices. In this study, we devised a simple method to fabricate double layer P-doped LIG electrodes through repetitive laser induction technology for high-performance flexible energy storage applications. Instead of utilizing commercial polyimide (PI) thin film, we optimized the formation process of P-doped PI thin film and achieved a highly flexible double layer P-doped LIG thin film electrode with a uniformly porous structure and the high porosity through repeated laser induction processes. Experimental results demonstrated that the developed double layer P-doped LIG thin film electrode exhibits high porosity, high specific areal capacitance of 180 mF cm−2, and high energy density of 0.025 mWh cm−2. Furthermore, an all-solid-state micro-supercapacitor utilizing hydrogel electrolyte was assembled, demonstrating a high areal capacitance of 62 mF cm−2 and excellent cycling stability with 95% capacitance retention after 6000 charging/discharging cycles. Moreover, the developed all-solid-state micro-supercapacitor successfully powered a light-emitting diode, showcasing its significant potential for practical energy storage applications.

Bio-inspired mobile robot design and autonomous exploration strategy for underground special space

PurposeTo make the robot that have real autonomous ability is always the goal of mobile robot research. For mobile robots, simultaneous localization and mapping (SLAM) research is no longer satisfied with enabling robots to build maps by remote control, more needs will focus on the autonomous exploration of unknown areas, which refer to the low light, complex spatial features and a series of unstructured environment, lick underground special space (dark and multiintersection). This study aims to propose a novel robot structure with mapping and autonomous exploration algorithms. The experiment proves the detection ability of the robot.Design/methodology/approachA small bio-inspired mobile robot suitable for underground special space (dark and multiintersection) is designed, and the control system is set up based on STM32 and Jetson Nano. The robot is equipped with double laser sensor and Ackerman chassis structure, which can adapt to the practical requirements of exploration in underground special space. Based on the graph optimization SLAM method, an optimization method for map construction is proposed. The Iterative Closest Point (ICP) algorithm is used to match two frames of laser to recalculate the relative pose of the robot, which improves the sensor utilization rate of the robot in underground space and also increase the synchronous positioning accuracy. Moreover, based on boundary cells and rapidly-exploring random tree (RRT) algorithm, a new Bio-RRT method for robot autonomous exploration is proposed in addition.FindingsAccording to the experimental results, it can be seen that the upgraded SLAM method proposed in this paper achieves better results in map construction. At the same time, the algorithm presents good real-time performance as well as high accuracy and strong maintainability, particularly it can update the map continuously with the passing of time and ensure the positioning accuracy in the process of map updating. The Bio-RRT method fused with the firing excitation mechanism of boundary cells has a more purposeful random tree growth. The number of random tree expansion nodes is less, and the amount of information to be processed is reduced, which leads to the path planning time shorter and the efficiency higher. In addition, the target bias makes the random tree grow directly toward the target point with a certain probability, and the obtained path nodes are basically distributed on or on both sides of the line between the initial point and the target point, which makes the path length shorter and reduces the moving cost of the mobile robot. The final experimental results demonstrate that the proposed upgraded SLAM and Bio-RRT methods can better complete the underground special space exploration task.Originality/valueBased on the background of robot autonomous exploration in underground special space, a new bio-inspired mobile robot structure with mapping and autonomous exploration algorithm is proposed in this paper. The robot structure is constructed, and the perceptual unit, control unit, driving unit and communication unit are described in detail. The robot can satisfy the practical requirements of exploring the underground dark and multiintersection space. Then, the upgraded graph optimization laser SLAM algorithm and interframe matching optimization method are proposed in this paper. The Bio-RRT independent exploration method is finally proposed, which takes shorter time in equally open space and the search strategy for multiintersection space is more efficient. The experimental results demonstrate that the proposed upgrade SLAM and Bio-RRT methods can better complete the underground space exploration task.

Transmission in graphene through a double laser barrier

We study the tunneling behavior of Dirac fermions in graphene subjected to a double barrier potential profile created by spatially overlapping laser fields. By modulating the graphene sheet with an oscillating structure formed from two laser barriers, we aim to understand how the transmission of Dirac fermions is influenced by such a light-induced electric potential landscape. Using the Floquet method, we determine the eigenspinors of the five regions defined by the barriers applied to the graphene sheet. Applying the continuity of the eigenspinors at barrier edges and using the transfer matrix method, we establish the transmission coefficients. These allow us to show that oscillating laser fields generate multiple transmission modes, including zero-photon transmission aligned with the central band ε and photon-assisted transmission at sidebands ε + l ϖ, with l = 0, ± 1, ⋯ and frequency ϖ. For numerical purposes, our attention is specifically directed towards transmissions related to zero-photon processes (l = 0), along with processes involving photon emission (l = 1) and absorption (l = − 1). We find that transmission occurs only when the incident energy is above the threshold energy ε > k y + 2ϖ, with transverse wave vector k y . We find that the variation in distance d 1 separating two barriers of widths d 2 − d 1 suppresses one transmission mode. Additionally, we show that an increase in laser intensity modifies transmission sharpness and amplitude.

Fundamental spatial mode high power 808 nm double trench wide ridge waveguide laser

—Lasers operating at a wavelength of 808 nm, with watt-level output power and high beam quality in the fundamental spatial mode, have garnered significant attention due to their potential applications across various fields. Transverse optical confinement in double trench ridge waveguide lasers is determined by the width of the ridge and the refractive index difference between the ridge and trench. In this study, we have designed and fabricated a wide ridge laser operating at 808 nm with high power output and stable fundamental spatial mode based on this principle. The fundamental spatial mode operation was successfully achieved with an 8 μm ridge waveguide laser, producing an impressive output power of 1.3 W. The device exhibits a stable far-field as the current was increased from 0.3 A to 1.8 A. The laser's output power exhibits a 14% reduction with an increase in temperature of 80 °C, demonstrating a decrease rate of only 1.25 mW/°C and a wavelength variation rate of 0.22 nm/°C, indicating low sensitivity to temperature changes.

Double-pulse-laser volumetric modification of fused silica: the effect of pulse delay on light propagation and energy deposition.

Volumetric modification of dielectrics by ultrashort laser pulses is a complex dynamic phenomenon involving material photoexcitation and associated nonlinear processes. To achieve control over modification, it is necessary to gain a deep insight into the dynamics of laser-excited processes that can be realized using double-laser-pulse experiments with different time separations supported by numerical simulations. In this paper, we apply this approach to investigate fused silica modification with femtosecond laser pulses that provides time-resolved information about the dynamic behavior of the laser-excited bandgap material. It is shown that the laser-generated free-electron plasma causes a shielding effect for the following pulse with a characteristic duration of ∼600 fs after the pulse action. Within this time interval, the second pulse produces a reduced modification as compared to a longer time separation between pulses. For double pulses with different energies, it was found that the volumetric modification is stronger when a lower-energy pulse couples with material first. This is explained by the combination of the effects of the re-excitation of self-trapped excitons, which are generated as a result of free electron recombination and associated light shielding. Experimental results are supported by numerical simulations of double laser pulse propagation in nonlinear media based on Maxwell's equations. Our findings offer a route for better controlling the inscription of 3D photonic structures in bulk optical materials.

Using double pulse laser ablation in air to enhance the strength of laser-driven shocks

In the process of multi-pulse laser ablation, inter-pulse delay time, Δt, is known to be an important parameter for maximizing ablation efficiency as well as impulse imparted to the target. In this work, using photon Doppler velocimetry, we show that for single pairs of colinear pulses (1064 nm, 8 ns, ∼ 60 J cm-2 per pulse) in air, the peak free surface velocity of the back surface of an aluminum target (125 µm thick) is increased, by a factor of nearly 3, when Δt = 10 microseconds, compared with both pulses arriving simultaneously (Δt = 0). Fast imaging of the ablation process suggests this enhancement is due to rarefaction of the contiguous air in the passage of the leading shock produced by ablation, which then in turn allows a larger fraction of the energy of the second pulse to reach the target surface. This interpretation is strengthened by additional experiments in which the two pulses do not overlap on the target surface, but the shock strength is nevertheless enhanced. Given a fixed energy budget this work suggests a prescription for maximizing laser-driven shock strength by judicious choice of inter-pulse delay.

Single-mode, surface-emitting quantum cascade laser at 26 μ m

We present the simulation, design, fabrication, and characterization of planarized double metal quantum cascade lasers based on InGaAs/GaAsSb. Intended for astrophysical heterodyne measurements and having the cavity embedded in benzocyclobutene, the devices are equipped with thermal bridges on either side of the ridge, in order to improve the heat dissipation. The lasers are shown to vertically emit a single mode around 26 μm in pulsed operation, with peak powers of ≈ 30 μW and a current density threshold of Jth = 3.7 kA/cm2. Maximum operation temperature is around 170 K, with the maximum supported duty cycle being extended from the initial 15% to about 30% with the help of the improved thermal management technique.

Characteristics of broadband OPCPA based on DKDP crystals with different deuterations for the SEL-100 PW laser system.

We present the performances of a broadband optical parametric chirped pulse amplification (OPCPA) using partially deuterated potassium dihydrogen phosphate (DKDP) crystals with deuteration levels of 70% and 98%. When pumped by a Nd:glass double frequency laser, the OPCPA system using the 98% deuterated DKDP crystal achieves a broad bandwidth of 189 nm (full width at 1/e2 maximum) from 836 nm to 1025 nm. For the DKDP crystal with length of 43 mm, the pump-to-signal conversion efficiency reaches 28.4% and the compressed pulse duration is 13.7 fs. For a 70% deuterated DKDP crystal with a length of 30 mm, the amplified spectrum ranges from 846-1021 nm, the compressed pulse duration is 15.7 fs, and the conversion efficiency is 25.5%. These results demonstrate the potential of DKDP crystals with higher deuteration as promising nonlinear crystals for use as final amplifiers in 100 Petawatt (PW) laser systems, supporting compression pulse duration shorter than 15 fs.

Flow Visualisation by Laser Sheet in a Smoke-Tunnel

The application of wind tunnel for visualizing flow over any bluff or streamline body plays an indispensable role in concepting various aerodynamical phenomenon such as formation of vortices, generating lift and drag, calculation of velocity vector and pressure profiles etc. Flow visualization through smoke and laser optics in a subsonic wind tunnel to capture vortex formation over airfoils, cylindrical and conical bodies is the experimental approach which has been studied and manifested elaborately in the article. Using smoke as a seeding material, the flow of the same is allowed to pass over the model which is illuminated via a double pulse laser beam to visualize the formation of vortex and capture the same for future references. The experimentation of the above models is carried out in a Honeycomb subsonic wind tunnel in the Aerodynamics Lab of Aerospace Engineering in the university. The article will cover Computational Fluid Dynamics (CFD) performed on ANSYS for the particular NACA series, Cross correlation PIV for plotting velocity vector for the captured images of the seed particles and the respective images of the entire experimental set-up. The images captured during this experiment can be later used by the aerodynamicists for optimizing aerodynamic efficiency of the experimented models depending on the vortex formation and flow pattern. The images can also be used for advance calculations required in Particle Image Velocimetry (PIV) for calculating velocity of every speed particle.

Using single and double laser pulses on the molecular Ni4@C48H36 system to design integrated nanospintronic units.

The accomplishment of long-distance spin transfer scenarios between several magnetic centers is a big challenge for building and supporting spin-logic units for developing future all-optical magnetic unit operations. Using high-level quantum chemistry theory CCSD and EOM-CCSD, we systematically study the ultrafast laser-induced spin-dynamics process on a carbon-based material, to which four magnetic centers are attached. We show that the CCSD method with the 6-31G basis set calculation is sensitive to the C-Ni bond length. The spin density distribution, which is computed using EOM-CCSD with LanL2DZ+ECP calculations, Mulliken population analysis, including spin-orbit-coupling (SOC) and a magnetic field, fulfills the requirements for achieving spin dynamics processes. Different local spin-flip and spin-transfer processes are accomplished within the subpicosecond regime. The impact of the propagation direction of the laser pulse by switching their polar and the azimuthal angles in spherical coordinates on the spin dynamics processes is analyzed. Double laser pulses with time delay δt ≥ 200 × FWHM yield in a realistic magnetic field gradient selectively a lateral resolution, which corresponds to distances smaller than the CMOS scale (2 nm in 2024) while our system size is comparable to the CMOS scale. Here Λ and V processes with two quasi-degenerate intermediate levels are used. We propose a model of an integrated spin-logic processor created from an array of individual spin-logic blocks, which are realized by four magnetic centers Ni. The findings of this study demonstrate the enormous potential of using laser-induced spin dynamics as the fundamental mechanism for future molecular magnetic technology.

Fabrication of bioinspired closed chute structure on TC4 surface by double laser beam ablation for enhanced dynamic anti-icing performance

The dynamic behavior of water droplets plays an important role in anti-icing performance, as when they impact on superhydrophobic surfaces, the rebound process effectively removes potential ice crystal nuclei on the surface, thereby reducing ice condensation and accumulation, ultimately preventing ice formation. In this study, inspired by the cuticle structure of springtails and the tilted arrangement of pigeon feathers, a bionic superhydrophobic surface with closed chute structure is proposed. The closed chute structure reduces the adhesion force between the surface and water droplets, enhancing directional rebounding ability and accelerating water droplets' separation from the surface for enhanced anti-icing performance. Considering the morphology of hierarchical closed structures is difficult to be regulated by single laser beam ablation, the superhydrophobic surface with closed chute structure is successfully fabricated by double laser beam ablation. This method optimizes the spatial distribution of the laser energy field by adjusting the rotation angle of the half-wave plate (HWP). By combining the analysis of micromorphology, elemental distribution, dynamic and static anti-icing tests etc., it is verified that the superhydrophobic surface with closed chute structure can improve the dynamic anti-icing performance, which provides a new method for anti-icing design in engineering field.

Designing a square periodic racemic helix photonic metamaterial using phase-controlled interference lithography for tailored chiral response

In this study, we propose a double exposure phase-controlled laser interference lithography (DE-PCLIL) approach in 4 + 1 beams interference to design a three-dimensional (3D) racemic helical periodic nanostructure. The explicit azimuthal rotation of each beam by π/2 between the two exposures and the resultant intensity distribution discover the racemic 3D helix structure arranged in the square unit cell. The proof of concept is experimentally demonstrated by recording a series of cross-sectional images at different z-planes of the volumetric interference pattern on a CMOS camera using a spatial light modulator (SLM). Additionally, we propose an approach to realize tapering in such a geometry through a slight variation of the interference angle in both exposures. We numerically investigated optical modes and circular dichroism (CD) characteristics of the racemic helix metamaterial. The racemic helix metamaterial structure offers an angle of incidence and polarization-insensitive coupled mode. Through numerical studies, we propose an alternative way to bring 3.4-fold CD signal enhancement by varying the phase of a particular handed helix only through modulating the local chiral field. Such 3D structure is profound with perfect absorption in broad spectral regions, potentially suited for plasmonic absorber-based photovoltaic and photo-catalysis applications.