Analytical and numerical investigations of displaced thermal state evolutions in a laser process

We investigate how displaced thermal states （DTSs） evolve in a laser channel. Remarkably, the initial DTS, an example of a mixed state, still remains mixed and thermal. At long times, they finally decay to a highly classical thermal field only related to the laser parameters κ and g. The normal ordering product of density operator of the DTS in the laser channel leads to obtaining the analytical time-evolution expressions of the photon number, Wigner function, and von Neumann entropy. Also, some interesting results are presented via numerically investigating these explicit time-dependent expressions.

Omnidirectional iridescence via cylindricallypolarized femtosecond laser processing

We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.

Microstructure of Laser Processed T10 Carbon Tool Steel

The microstructure of the laser melted 1.0%C tool steel have been investigated.The region affected by the laser can be subdivided into 3 zones,which consist of a melted region at the surface,a zone with solid state transformation and the area adjacent to the unaffected substrate where cementite is slightly dissolved.The melted zone possessed a cellular growth morphology consisting of austenite and martensite.The carbon content of the austenite was measured to be over 1 wt-%.A great deal of retained austenite and twinned martensite were found in the first two zones(the melted and solid transformed).

The Characteristics of the Surface Topography of Excimer Laser Processed Al_2O_3 Ceramic

Surface of Al 2O 3 ceramic was processed by an excimer laser and the characteristics of topography were examined based on the application of the microelectromechanical system(MEMS). It is indicated that the statistic parameters of surface topography processed by the excimer laser have an obvious regularity. The arithmetic-mean value R a and the root-mean square value R q change with the changing of processing parameters in the same step and trend, and there is a quantitative relation between them.A simplified model is proposed for the excimer laser processing surface profile, whose results of the analysis and calculation agree basically with the experimental data. Furthermore,the surfaces processed by excimer laser are greatly flat. Skewness root-mean-square value Z· q changed little with the change of the technological parameters. The above characteristics depend on the processing principle of excimer laser, quite different from the cutting processing.

RETAINED AUSTENITE IN LASER PROCESSED STEELS

This paper Presents experimental data on effect of carbon concentration and laser processing regimes on retained austenite quantity. The data on retained austenite decomposition during subsequent temperings at various temperatures as well as after holding at room temperature during 3 years are given.Correla- tion between structural broadening of the X - ray lines of retained gamma - phase and the amount of the latter has been discovered.Mechanisms responsible for the increased quantity of the retained austen- ite in carbon and low alloyed steels after laser hardening are described.

The Application of Laser Processing on Clutch Manufacture

The first multi-function laser processing system in the domestic for clutch manufacture,with abilities of cutting, jointing and heat treatment,was reported in this paper.One external optical path,double laser heads,adjust device by manual operation,automatically track were employed in this system Also the other parts of vehicles can be fabricated by this system,as well as clutches.The special processing to manufacture the clutches of heavy vehicles,which was developed by the project of this laser processing system,achieved the international standards and satisfied the economic development and nation defense in the do- mestic.

Effect of pulsed laser process parameters on welding quality of automobile fuel injector

In this research, pulverization plate and base of a fuel injector in an automobile electronic-controlled engine was joined by pulsed laser welding. The different welding parameters were evaluated and effect of process parameters on joint characteristics was analyzed. The optimal process parameters were obtained as follows： welding current 120 A, welding speed 600 ram/rain, pulse duration 1.80 ms and pulse frequency 60 Hz. The microstructure of weld metal was investigated. Results show that the fusion zone is austenitic dendrite, the weld center is equiaxed grain, while the transition zone between fusion zone and weld center is mixed crystal with austenitic dendrite and equiaxed grain. The weld layered phenomenon was observed, and eddy caused by keyhole effect is the main reason for the formation of layered structure in molten pool.

Present Situation and Developing Trend on Laser Processing Industry in China

Developing trend and present situation on laser processing industry in China are mainly reviewed.The market analysis on laser processing systems are given,some new and rapidly developed laser processing systems are introduced.Finally,the paper also introduces some new kinds of laser systems and equipment.

Fourier hologram method using Gerchberg-Saxton algorithm for parallel femtosecond laser processing

In order to improve femtosecond laser throughput,a parallel processing system consisting of liquid crystal on silicon(LCOS)device as spatial light modulator is put forward.A method is described for displaying Fourier hologram on LCOS,and a high uniformity of several diffraction peaks in the computer reconstruction is achieved.Application of this method to the parallel femtosecond laser processing is also demonstrated,and two intersecting rings and three tangent rings are fabricated respectively by one time in the photoresist.

A Novel Approach for the Fabrication of Sharkskin Structured Bionic Surfaces with Hydrophobic Wettability:Laser Processing and Ordered Abrasive Belt Grinding

A new process for the fabrication of sharkskin bionic structures on metal surfaces is proposed.The sharkskin bionic surface was successfully machined on the surface of IN718 by laser sequencing of the abrasive belt surface,laser processing of the layered scale-like structure,and ribbed texture grinding.The flexible contact properties of belt grinding allow ribbed structures to be machined uniformly on a hierarchical,scale-like microstructure.Sharkskin bionic microstructures with radii greater than 75µm were prepared after parameter optimisation.The influence of processing parameters on the geometrical accuracy of the microstructure was investigated,the microstructure microform and elemental distribution were analyzed,and the relationship between the ribbed microstructure and chemical properties of the surface of the bionic sharkskin on wettability was revealed.The results indicate that reducing the laser power and increasing the laser scan rate can reduce the laser thermal effect and improve the microstructure processing accuracy.The laser ablation process is accompanied by a violent chemical reaction that introduces a large amount of oxygen and carbon elements and infiltrates them at a certain depth.The wettability of the surface undergoes a transition from hydrophilic(contact angle 69.72°)to hydrophobic(contact angle 131.56°)due to the adsorption of C-C/C-H and the reduction of C=O/O=C-O during the placement process.The ribbed microstructure changes the solid-liquid contact on the surface into a solid-liquid-gas contact,which has an enhanced effect on hydrophobicity.This study is a valuable guide to the processing of hydrophobic layered bionic microstructures.

Effect of Laser Processing Pattern on the Mechanical Properties of Aluminum Alloy Adhesive Joints

Adhesive bonding is a promising joining technology for joining lightweight aluminum structures,offering advantages such as the absence of additional heat input,connection damage,and environmental pollution.To further enhance the strength of aluminum adhesive joints,this study investigates the influence of laser surface treatment on their mechanical properties.Specifically,the effect of laser processing patterns and their geometric parameters on aluminum alloy adhesive joints is examined.A fiber laser is used to process crater array and multi-groove pattern on A6061 aluminum surface.The impact of crater overlap ratio and groove distance on various aspects,including aluminum surface morphology,roughness(Sa),adhesive joints shear,tensile strength,and failure modes is discussed.Laser confocal microscope tests,water contact angle tests,lap shear tests,and cross tensile tests are employed to analyze these parameters.The results indicate that as the crater overlap ratio increases,the S_(a) value of the aluminum surface increases.Moreover,the shear strength of adhesive joints initially increases and then decreases,while the tensile strength consistently increases.On the other hand,an increase in groove distance leads to a decrease in S_(a),as well as a reduction in both shear and tensile strength of adhesive joints.For shear loading conditions,mechanical interlocking is identified as one of the bonding mechanisms in aluminum adhesive joints featuring crater array and multi-groove patterns.The formation of interlocking structures is found to be influenced by the aluminum surface pattern and its associated parameters,as revealed through failure surface analysis.Specifically,adhesive and crater or groove interactions contribute to the formation of interlocking structures in specimens with a crater overlap ratio of -60% or groove distances of 120,180,300,and 400μm.Conversely,specimens with overlap ratios of 0%,40%,and 60% exhibit interlocking structures formed by the adhesive and crater edge.

Femtosecond laser processing of microcavity lasers

In this paper, we reviewed the fabrications of functional microcavity lasers in soft materials such as polymer and protein by femtosecond laser processing. High-quality （Q） microdisks with a laser dye （Rhodamine B, RhB） acting as gain medium were fabricated that produced whispering-gallery-mode （WGM） lasing output. We also obtained unidirectional lasing output with a low lasing threshold in a deformed spiral microcavity at room temperature. Photonic-molecule （PM） microlasers were prepared to investigate the interaction and coupling effects of different cavities, and it was found that the distance between the two disks plays an important role in the lasing behaviors. Single-mode lasing was realized from a stacked PM microlaser through Vernier effect. Furthermore we adopted the biocompatible materials, RhB-doped proteins as a host material and fabricated a three-dimensional （3D） WGM microlaser, which operated well both in air and aqueous environment. The sensing of the protein micro- lasers to Na2SO4 concentration was investigated. Our results of fabricating high-Q microlasers with different materials reveal the potential applications of femtosecond laser processing in the areas of integrated optoelectronic and ultrahigh sensitive bio-sensing devices.

Evolution law of Wigner function in laser process

Based on the density operator＇s operator-sum representation recently obtained by Fan and Hu for a laser process （Opt. Commun., 2008, 281： 5571; Opt. Commun., 2009, 282： 932; Phys. Lett. B, 2008, 22： 2435）, we derive the evolution law of Wigner operator, the law is concisely expressed in T exp[-2T（ate-（k-g）t - a.）（ae-（k-g）t a）]; where g the normally ordered form A（a,a＊,t） = -T/π., and a are the cavity gain and the loss, respectively, and T - （a - g）（g-t-g - 2ge-2（k-g）t）-1. When 1 exp[-2（at a＊）（a a）] which is the initial Wigner operator. Using this t = O, A（a,a＊,t） →1/π , formalism the evolution law of Wigner functions in laser process can be directly obtained.

Osteogenic and antibacterial ability of micro-nano structures coated with ZnO on Ti-6Al-4V implant fabricated by two-step laser processing

The biological performance of Ti-6Al-4V implant is primarily determined by their surface properties.However,traditional surface modification methods,such as acid etching,hardly make improvement in their osseointegration ability and antibacterial capacity.In this study,we prepared a multi-scale composite structure coated with zinc oxide(ZnO)on Ti-6Al-4V implant by an innovative technology of two-step laser processing combined with solution-assistant.Compared with the acid etching method,the physicochemical properties of surface significantly improved.The in vitro results showed that the particular dimension of micro-nano structure and the multifaceted nature of ZnO synergistically affected MC3T3-E1 osteogenesis and bacterial activities:(1)The surface morphology showed a‘contact guidance'effect on cell arrangement,which was conducive to the adhesion of filopodia and cell spreading,and the osteogenesis level of MC3T3-E1 was enhanced due to the release of zinc ions(Zn^(2+));(2)the characterization of bacterial response revealed that periodic nanostructures and Zn^(2+)released could cause damage to the cell wall of E.coli and reduce the adhesion and aggregation of S.aureus.In conclusion,the modified surface showed a synergistic effect of physical topography and chemical composition,making this a promising method and providing new insight into bone defect repairment.

The Effect of Laser Sintering Process Parameters on Cu Nanoparticle Ink in Room Conditions

Copper is an interesting material for printed electronics inks because, for example, of its good conductivity and lower raw material price compared to silver. However, post-processing Cu inks is challenging because of non-conductive copper oxide. In this work, inkjet-printed Cu nanoparticle structures were sintered on a polyimide substrate with a continuous-wave 808-nm diode laser. Laser sintering was tested by varying the sintering parameters (optical power and scanning velocity), and the electrical resistance of the samples was measured. A minimum sheet resistance of approx.90 mΩ/□ was obtained. All tests were run in room conditions. Sintered structures were then analyzed from SEM images. Results showed that laser sintering produces good repeatability, that a scanning velocity increment positively affects the process window, and that multiple sintering cycles do not increase conductivity.

Quantitative Analysis of Composition Change in AZ31 Magnesium Alloy Using CF-LIBS After Laser Material Processing

The concentration of elements in molten metal of AZ31 magnesium alloy after long pulsed Nd：YAG laser processing was quantitatively analyzed by using calibration-free laser-induced breakdown spectroscopy （CF-LIBS）. The composition change in AZ31 magnesium alloy under different laser pulse width was also investigated. The experimental results showed that CF-LIBS can obtain satisfactory quantitative or semi-quantitative results for matrix or major elements, while only qualitative analysis was possible for minor or trace elements. Moreover, it is found that the chemical composition of molten metal will change after laser processing. The concentration of magnesium in molten metal is lower than that present in the base metal. The Mg loss increases with an increase of pulse width in the laser processing. This result shows that the selective vaporization of different elements is affected by the pulse width during laser processing.

EFFECT OF LASER MELTING PROCESSING ON MICROSTRUCTURE OF GRAY CAST IRON

The microstructure of the laser hardened layer on the HT20-40 gray cast iron after laser melting processing'was examined by optical microscopy,transmission electron microscopy (TEM)and scanning electron microscopy(SEM).Experimental results showed that a struc- ture with dendritic(M+A')and interdendriticly laminal transformed ledeburite (M+A'+Fe_3C)was produced after laser melting processing.The martensite is a mixture of dis- location martensite and twin martensite.Dislocation pile-ups and twins were found in the residual austenite.Microsegregation of composition and heterogeneity of microstructure were also apparent after laser melting processing.

Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality(IAQ) directly affects the health of occupants. Household manufacturing equipment(HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment(HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration(PNC) and particle emission rate(PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 m W, the mode diameters of particles were < 150 nm, and PNCs were > 2.0 × 10^(4) particles/cm^(3). Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C 8 aromatics(ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles(UFPs) was > 5 × 10^(4) particles/cm^(3) during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.

A zone-layered trimming method for ceramic core of aero-engine blade based on an advanced reconfigurable laser processing system

Ceramic structural parts are one of the most widely utilized structural parts in the industry. However, they usually contain defects following the pressing process, such as burrs. Therefore, additional trimming is usually required, despite the deformation challenges and difficulty in positioning. This paper proposes an ultrafast laser processing system for trimming complex ceramic structural parts. Opto-electromechanical cooperative control software is developed to control the laser processing system. The trimming problem of the ceramic cores used in aero engines is studied. The regional registration method is introduced based on the iterative closest point algorithm to register the path extracted from the computer-aided design model with the deformed ceramic core. A zonal and layering processing method for three-dimensional contours on complex surfaces is proposed to generate the working data of high-speed scanning galvanometer and the computer numerical control machine tool, respectively. The results show that the laser system and the method proposed in this paper are suitable for trimming complex non-datum parts such as ceramic cores. Compared with the results of manual trimming, the method proposed in this paper has higher accuracy, efficiency, and yield. The method mentioned above has been used in practical application with satisfactory results.

New application of non-Hermitian Hamiltonian operator in solving master equation for laser process

We find that laser process can be equivalently described by a symplectic evolution in the context of thermo field dynamics, and the corresponding coherent state evolution for the corresponding master equation is recognized. More interestingly, this embodies a new application of non-Hermitian Hamiltonian operator which can well expose the entanglement between the system and its environment.