The selective laser melting (SLM) is an advanced rapid prototyping technology developed in recent decades by using high energy laser beam to melt metal powder layer by layer. At present, the research on aluminum alloy by SLM at home is mainly concentrated on the Al-Si powder, and the research on the 7 series ultra-high strength aluminum alloy by SLM is still in the initial stage. A series of experiments were carried out on 7075 aluminum alloy powder for the SLM forming process. The microstructure properties and cracks of the 7075 aluminum alloy by SLM samples were analyzed by means of metallographic microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and other instruments. The results show that the crack in the sample is caused by component segregation, second T phase and η′(MgZn2) phase non-equilibrium phase precipitate because of component segregation. And with the increase of the laser energy density, the columnar crystal length, the depth of the molten pool, the mean length of the crack and the tensile strength of the sample increase, the number of cracks decreases.

Additive manufacturing can rapidly and directly produce metal parts with complex geometries, while significantly improving material utilization and reducing costs. Additive manufacturing parts still have a certain gap with forgings in key properties such as fatigue, and it is necessary to find an effective post-processing method. Additive manufactured TC4 was treated by laser peening, and the surface integrity improvement effect of TC4 titanium alloy was investigated. The strengthening effect was compared with the same grade conventional forged titanium alloy. The results show that laser peening has little effect on the surface roughness of the two materials. Furthermore, the surface microhardness of additive manufactured TC4 increased from 348 HV to 367 HV, and the hardening layer reached a thickness of 0.75 mm, while the surface microhardness of wrought TC4 increased from 315 HV to 362 HV, and the hardening layer reached a thickness more than 1 mm. Compressive residual stress was induced into the subsurface of the samples with a maximum value around 400 MPa for the additive manufactured TC4. The affected zone depth was around 0.75 mm. For the wrought TC4, the compressive residual stress was induced into the subsurface of the samples with a maximum value around 600 MPa. The affected zone depth was more than 1 mm. In addition, the density of additive manufactured TC4 was measured by the Archimedes method. The density of additive manufactured TC4 was 98.46%, while the density became 98.92% after one shock of laser peening. Compared with wrought TC4, the relative porosity of additive manufactured TC4 may be the reason for the smaller residual stress amplitude and shallow affected depth by laser peening.

316L stainless steel parts were manufactured on TB-100 selective laser melting equipment with independent intellectual property rights. The low-magnification defects of forming parts with different process parameters (laser power, scanning speed and scanning distance) were studied by metallographic microscope, mainly air bubbles, pores, microcracks and macrocracks. The formation mechanism of various kinds of defects were analyzed. the microstructure and composition of the defects were studied by means of SEM and EDS. The results show that the pores are mainly circular air pores, irregular process pores and oxide inclusions. The air bubbles are mainly hydrogen bubbles and nitrogen bubbles, while the microcracks are mainly caused by penetrating pores and thermal cracks caused by excessive internal stress, macrocracks are mainly the layer cracks caused by excessive residual stress, which belong to cold crack. Linear energy density (E＝P/v) is introduced as a synthetic parameter. As the line energy density increases, the pores decrease gradually. However, when the linear energy density reaches 400 J/m, cracks appear, and a large number of air bubbles defects appear. As the linear energy density continues to increase, the cracks increases gradually. When the linear energy density reaches 583 J/m, the defects were mainly cracks and bubbles decrease. When the linear energy density reaches 875 J/m, the cracks are strip-shaped and the size is significantly increased, and cracks are connected to each other. According to the analysis and test verification, the optimal process parameters of 316L stainless steel are laser power 190～210 kW, laser speed 800～1 000 mm/s and scanning interval 0.90～0.11 mm, and the linear energy density is about 200 J/m. There are no cracks, basically no bubbles, a small amount of pores, and the product density reaches 99.7%.

In order to utilize the laser cladding technology to achieve the additive manufacturing of the knife blade edge of the die-cutting machine, the laser power, scanning speed and defocusing amount are the influencing factors, and the single-pass laser cladding of WC-reinforced Ni-based mixed powder is performed on the surface of the 45 steel. The experiment was conducted to prepare a single-pass laser cladding gradient coating, and the microstructure structure, defect rate, residual stress and microhardness of the cladding layer were analyzed. According to the analysis results, the microstructure of the cladding layer shows obvious stratification which is conducive to improving the performance of the cladding layer. The defect rate increases with the increase of the scanning speed and the defocus amount, and increases first and then decreases with the increase of laser power. The scanning speed has a significant effect on the defect rate. The difference in temperature between the cladding layer and the substrate and the difference in thermal expansion coefficient between the cladding layer and the substrate during the cladding process are the main causes of residual stress. The influence of each factor on the residual stress is: scanning speed＞laser power＞defocusing amount. The structure of stratified layers helps to reduce the difference of linear expansion coefficient between the cladding layer and the substrate. The microhardness increases stepwise from the substrate to the top of the cladding layer. The microhardness of the top of the cladding layer can reach 70 HRC, which is about 3 to 4 times that of the substrate. It is superior to the actual performance of large-scale use of the imported powder metallurgy carbide die-cutting machine knife blade hardness (63 HRC).

In order to study the effect of laser power on the microstructure and properties of laser cladding 304 stainless steel, the process of laser cladding 304 stainless steel at different laser power was simulated by using ANSYS software. The temperature field under different laser powers was analyzed, and a temperature-time curve at a point 1 mm from the surface of the cladding layer was obtained. A single laser cladding 304 stainless steel experiment was carried out on the surface of 27SiMn steel, and the microstructure, macroscopic morphology and microhardness were analyzed. The results show that the width, depth and area of the temperature field by numerical simulation increase with the increase of laser power. The temperature time cure of this point changes in a sawtooth shape, and the maximum temperature increases with the increase of laser power. Under different laser power, good metallurgical bonding is achieved between the cladding layer and the substrate. The laser power is in the range of 2 100 W to 2 500 W. With the increase of laser power, the grains of the cladding layer become finer and the structure is more compact. When the laser power is 2 700 W, the cladding grain is larger than the power of 2 500 W. The microhardness curves show a step-shaped distribution trend of "low-high-low".

The single pass orthogonal test was carried out for Ni204 by laser cladding technology. The geometry size and microstructure of the clad track were measured by laser confocal microscopy. The effects of different process parameters on the morphology and microstructure of the samples were analyzed by variance analysis. The results show that the power has the most significant influence on the melting width and depth. The influence of scanning speed on the melting height, the ratio of width and height and wetting angle was most significant. When the energy density is too small, the Ni204 alloy powder does not generate a molten pool on the substrate. The microstructure at the boundary of the molten pool is columnar crystal. In the molten pool, the grain growth time is short and recrystallization is not easy, and the molten pool is dendritic. Through analysis, the optimal process parameter groups were Lp＝750 W, Pfr＝0.8 r/min, Ss＝480 mm/min and Lp＝900 W, Pfr＝1 r/min, Ss＝480 mm/min which can ensure the horizontal and vertical overlap without reducing the cladding efficiency.

GH4169 samples were prepared by selective laser melting technique. The macroscopic and microscopic structure morphology and mechanical properties of the manufactured parts were analyzed by optical microscope, scanning electron microscope and electronic universal material testing machine. The results show that the crystal morphology of SLM molded parts is mainly cellular crystal, the diameter of fine columnar crystal is about 0.1～1.0 μm inside the "micro-melting pools", and the cross section is approximate hexagonal shape. Due to the different angles of laser incidence, powder uneven, temperature accumulation and change in heat dissipation conditions during the SLM process, the shape, length, width of the columnar crystal is different in the "micro-melting pools". The tensile specimens of SLM GH4169 molded parts present ductile fracture + cleavage fracture mode.

According to the feature of the easy wear of agricultural machine tools, use laser remanufacturing method to produce NiCr＋WC coating on the surface of farm tools steel. The microstructure of the coating and the interface between the coating and the substrate was analyzed. The temperature field of the remanufacturing layer and its interface was simulated by Abaqus. The experimental results show that using laser remanufacturing method can successfully prepare a wear-resistant layer with good metallurgical bonding with the substrate. The SEM analysis shows that WC of coating and NiCr alloy form a good composite material, and the grains in the coating are refined. The hard WC particles are evenly distributed on NiCr alloy base material, forming a good bonding interface. The simulation results are consistent with the temperature field distribution of the experimental results.

Graphite parts prepared by selective laser sintering technology have poor porosity, bending strength and poor electrical conductivity, and are difficult to directly use as functional structural parts. In this paper, the effects of two post-treatment processes on the overall performance of SLS graphite parts are compared. Studies have shown that the vacuum pressure impregnation of phenolic resin solution has limited performance improvement on SLS graphite parts. After three vacuum pressure impregnation, carbonization and high temperature sintering, the sample density can reach 1.24 g/cm3, correspondingly the flexural strength and conductivity reached 27.11 MPa and 253.80 S/cm, further difficulty is more difficult; and the hot pressing curing process is relatively easy to densify. Under the pressure of 3.00 MPa, the sample density can reach 1.59 g/cm3, after carbonization and high temperature sintering. Its flexural strength and electrical conductivity reach 33.88 MPa and 380.98 S/cm. Finally, the feasibility of the above process was verified by post-processing the porous graphite skeleton and graphite mold.

The Al-12%Si alloy powder with particle size of 50～100 μm was printed on 6063 aluminum alloy substrate by powder feeding laser melting 3D printing device. The microstructure evolution of 3D printing Al-12%Si alloy with/without transverse steady magnetic field was studied. The results show that the deposited samples obtained by laser melting show obvious laminar accumulation characteristics, and the composition contains a bright white α-Al phase and an Al-Si eutectic phase and a part of the darker α-Al phase, and the sample density reaches 94%. At the magnetic field strength of 0.5 T, the bead interface is formed in the bottom region of the sample and a plurality of equiaxed α-Al phases are formed at the edges. The magnetic field has the effect of converting the columnar crystals into equiaxed crystals. Moreover, the α-Al phase can be converted from a columnar crystal to an equiaxed crystal, and a high-order dendritic arm can be formed.

Ti6Al4V is an ideal biomedical material with good biocompatibility and excellent mechanical properties, and 3D printing technology is a revolutionary manufacturing technology that can personalized biomedical materials. Therefore, the use of 3D printing technology to prepare Ti6Al4V implants has become one of the hotspots in tissue engineering research in recent years. However, there are a large number of randomly distributed spherical cavities inside Ti6Al4V prepared by 3D printing technology, which hinders the wide use of 3D printed titanium alloy. The formation mechanism of internal cavities of titanium alloy prepared by selective laser melting and electron beam melting deposition is summarized. The effects of high energy beam energy density and scanning strategy on the cavities are analyzed, and the effect of internal cavities on the tensile and fatigue properties of the printed parts is revealed.

Fiber laser welding of low alloy high strength steel HC420LA was carried out with different laser power and defocusing distance. The effects of power and defocusing distance on the morphology, microstructure, hardness distribution and tensile properties of the joints were studied. The results show that the welded joints without porosity and crack can be obtained by fiber laser welding of the steel plate of HC420LA. When the laser welding power is 1 000 W, the weld formation is better. With the increase of laser power, the weld width increases, and the lower surface has a slight arc pit. The negative defocusingdistance has a significant effect on the weld section shape, and the ratio of upper and lower melting width increases with the increase of negative defocusingdistance.The main microstructure in the weld zone of laser welded HC420LA steel consists of martensite, ferrite and bainite. There is no softening zone in welded joint, and the hardness of weld is higher than that of heat affected zone and base metal. With the increase of power, the hardness of weld decreases gradually. The hardness of weld with larger negative defocusing distance is slightly higher than that with positive defocusing distance. In the direction perpendicular to the weld, the tensile strength of the welded joint is higher than that of the base metal. The strength-ductility balance of the weld increases slightly with the increase of power, and the change of the defocusing distance has a great influence on the strength-ductility balance, but there is no obvious rule.

TC4 titanium alloy bottom-locking joint with a thickness of 3 mm was welded by disk laser. The type of porosity was judged by analyzing the pores characteristics. The suppress effects of porosity were studied by using three welding methods: pulsed laser welding, laser heat-conduction welding and defocused laser beam-high speed welding. The results show that a large number of porosities exist in the center of the weld, the porosity is irregular and large, and the surface of the porosity wall is rough, mainly for small pores. By using pulsed laser welding with lower welding speed and appropriate pulse frequency, the porosity is decreased to 0.5%～1%. By using laser heat-conduction welding with 0.4 m/min of welding speed, ＋15 mm of laser beam defocusing distance, the porosity is 0%, but the welding deformation is large and incomplete penetration defect is possibly formed. By using defocused laser beam-high speed welding, the porosity is obviously decreased with higher welding speed and longer laser beam defocusing distance. At the parameter of 2～3 m/min of welding speed, ＋5～＋7 mm of laser beam defocusing distance, the porosity is 0%～5%, and the porosity is significantly and stably suppressed.

Laser transmission welding is widely used in medical, electronics, automobile and package fields due to its excellent welding performance. At present, fiberglass-doped is an important method of modified plastic for improving the usability of plastic products. However, fiberglass-doped method can contribute to a sharp decline in plastic laser transmittance, and it presents a technology difficulty for laser transmission welding. To solve this problem, a technology study of laser transmission welding of fiberglass-doped ABS and PP is carried out in order to obtain the best welding process. Firstly, according to the mechanism of laser transmission welding, the process problems of welding fiberglass-doped ABS and PP are pointed out. Secondly, the preliminary welding experiment of fiberglass-doped ABS and PP is implemented to obtain the suitable scope of welding process parameters. Then, the Taguchi experiment is accomplished to analyze the effects of process parameters on shear strength through proposing the concept of laser energy per unit of area. The experiment analysis shows that the laser energy per unit of area can well describe the relationship between weld shear strength and process parameters. Besides, the optimal laser energy per unit of area for welding fiberglass-doped ABS and PP is 0.43 J/mm2.

Welding 10 mm Q345B steel plate by using laser-MAG hybrid welding, the effects of laser power, MAG current, defocusing amount and welding speed on weld penetration and width were analyzed by multiple linear regression method. The MATLAB algorithm was used to optimize the model and get the best combination of welding process parameters. The experimental results show that when the laser power is 3 kW, the current is 320 A, the defocusing amount is-2 mm, and the welding speed is 8.3 mm/s, the weld penetration width ratio is maximized, and the verification result is not more than 5% from the actual value, the mathematical model can effectively predict the welding quality.

In order to study the influence of the processing environment on the infiltration property of laser-induced aluminum plates, pure aluminum plates were processed with a nanosecond laser under vacuum and air atmosphere, respectively. The effects of vacuum and air atmosphere on the surface microstructure of the laser-induced aluminum sheets were compared and analyzed by using an optical surface profilometer and a scanning electron microscope (SEM). The effects of vacuum and air different processing environments and different storage environments on the infiltration property of the sample were compared and analyzed by a contact angle measuring instrument. The results show that under the same laser parameters, the surface roughness of the sample processed in the vacuum environment is obviously smaller than that processed in the air. While the samples processed in the air environment have the property of changing from super-hydrophilic to hydrophobic or even super-hydrophobic, the samples processed in the vacuum environment keep constant hydrophilic properties. Moreover, samples processed with laser in the air and then heat-treated in vacuum are more favorable for the conversion of their infiltration properties, which can greatly improve the efficiency of preparing the super-hydrophobic aluminum plate.

A small amount of micro-pores are formed on the substrate surface of some materials after laser cladding, and the existence of the micro-pores directly results in the mechanical properties of the material during the laser shock peening. The numerical simulation of micro-pores integrated laser shock peening of aluminum alloys was carried out. The two-dimensional axisymmetric finite element models of homogeneous substrate and micro-pore substrate were established in ABAQUS finite element software. The effects of micro-pores in the cladding layer on the velocity, the residual stress field, the plastic deformation and the energy change of the shock wave during laser shock processing were researched. The basic mechanisms of these effects have been systematically studied. The numerical simulation results show that there is significant compressive stress around the micropores compared with the homogeneous substrate. The existence of micro-pores weakens the propagation velocity of the shock wave, and the wave velocity decreases by about 3.94%. In addition, the existence of the micro-pores affects the final energy absorption.

Aiming at the problem that the external parameters of the on-vehicle 3D LIDAR needs to be calibrated before installation, a calibration method for LIDAR external parameters is proposed under the consideration of LADAR's invisible scanning beam and multi-line scanning. Firstly, scanning a ordinary carton, and the random sample consensus algorithm (RANSAC) is used to fit the initial model of three planes in the obtained point cloud data, with the vertical relationship between the two sides of the carton and the ground as a constraint. Then the rotation and translation steps are used to optimize the fitting precision of the plane model, and the corresponding vector and point are extracted from the optimal model. Next, solving the rotation and translation parameters of the LIDAR using the transformation model of 3D coordinate system based on space vector, calibration of all external parameters can be done by collecting data once. Finally, the effectiveness of the algorithm is verified by the simulation and the results of 3D reconstruction of the outdoor environment after calibration.

The existing traffic sign recognition technology has the problems of high recognition rate, high power consumption or low recognition rate and low power consumption. Aiming at this problem, a new light WACNN of recognition algorithm is constructed. Firstly, six layers convolutional neural network are constructed by using TensorFlow, in which the first three layers are convolutional pooling layers, the fourth layer is 1×1 convolutional layer, the fifth layer is fully connected layer, the sixth layer is output layer, and the first four layers are then added batch normalization method. Secondly, histogram equalization is used to preprocess traffic sign images. Finally, the model is tested on GTSR. The experimental results show that the proposed model not only greatly shortens the training time, but also the recognition accuracy can reach 97%.

optical fiber sensing was proposed, and the measurement principle and key technologies of the system were studied. Through modeling and analyzing the intensity of the emitted light of the fiber-optic sensor emitting fiber, the corresponding relationship between the intensity-enhanced function and the measured distance was found. Aiming at the influence of the stability of the light source in the measurement system and the change of the surface reflectivity of the workpiece on the topography measurement, proposed a compensation technique to increase the reference light path. The experimental results show that the calibrated displacement modulation characteristic curve has good repeatability, the repeatability error is 3.82%, and the linear range of the curve slope is 0.2～0.6 mm, and the sensitivity is 1.11 mW/mm, the micro-displacement measurement is performed in the linear interval, and the average absolute error of the measurement is 2.8 μm. The step of the workpiece with a height calibration of 100.0 μm is measured 10 times, and the average absolute error of the step height is 6.2 μm, which indicates that the measurement system can better measure the surface topography of the work piece.

With the improvement of living standards, people pay more and more attention to food safety issues, and counterfeit wine is an inescapable topic in food safety. The rapid and accurate identification of different brands of wine has great reality for counterfeit wine identification and food safety. Based on this, a method for rapid identification of different brands of white wine by XGBoost algorithm combined with laser-induced fluorescence (LIF) was proposed. The laser-induced fluorescence technique was used to collect the fluorescence spectrum of liquor, and then the raw spectrum data of the obtained liquor was identified by XGBoost algorithm. The experiments took 40° and 45° liquor as the research object, selected 6 kinds of wine samples, collected 40 sets of spectra for each wine sample, randomly selected 30 sets for XGBoost model training, and the remaining 10 groups were used for training good model test. In the experiment, the training time of the XGBoost algorithm is 0.172 s, and the trained model test recognition rate is 98.33%. The experimental results show that the XGBoost algorithm combined with laser-induced fluorescence technology can quickly and accurately identify different brands of liquor.

The domestic high-power RF slab CO2 laser has no dielectric film on the surface of the copper electrode. The surface of the bare copper is easily oxidized during the discharge process. It is damaged by laser electronic sputtering. The waveguide loss is seriously, which affects the light output efficiency of the laser. In order to solve the above problems, the Al＋Al2O3 hybrid waveguide dielectric film was developed. The composition of electrode film was analyzed and the anti-electron sputtering ability was tested. Experiments was conducted to detect the anomalous dispersion of CO2optical waves on the film surface. The micro analysis shows the film is composite of Al and O, the atomic ratio is over 2∶3, and the micro-structure is Al＋Al2O3, which meets the design of electrode surface film structure; the reflectance under different incident angle was tested, when incident angle is between 10°to 170°, the highest reflectance of Al2O3 film surface to CO2 with a wavelength of 10.6 μm is 85%. Discharge test shows the average optical efficiency of coated electrode laser is 10.4%. However, that of naked Cu electrode laser is 6.5%.

An all polarization-maintaining fiber laser system consisting of a low repetition rate mode-locked oscillator based on nonlinear amplified loop mirror cascaded with two-stage amplifiers are introduced. The experimental result shows that the output of the oscillating cavity is a stable mode-locked pulse with a maximum chirp, the pulse width is 90.25 ps, the corresponding Fourier transform limit is 141 fs, and it can be compressed to 431 fs with a center wavelength of 1064 nm and a 3 db spectral width of 10.4 nm. After the two-stage amplifier, the pulse average power can be amplified to 2.1 W, and the average output power is 1.5 W and the pulse width is 417 fs after compression using the grating pair. The whole system can obtain low repetition rate and high energy pulses output without passing through the acousto-optic modulator, which is a new idea to improve the pulse energy, and also facilitates the miniaturization of the mode-locked laser.

The miniaturization is the current development trend of pulsed laser proximity fuze. In addition to considering the impact of structural overload, the problem of space electromagnetic interference caused by the miniaturization of the structure can not be ignored. Based on the miniaturization background, a theoretical model of pulsed laser emission system is established, and the instantaneous discharge peripheral radiation is simulated by Comsol software. Analyzing the electromagnetic radiation interference on the detection system caused by the pulse current of the emission system, it proposes the anti-electromagnetic radiation interference measures based on the electromagnetic shielding mechanism. The experimental and simulation results show that the instantaneous discharge of the laser emission system will produce great electromagnetic radiation interference effectively suppressed by the 45 steel combined shielding mechanism.

According to the working characteristics of He-Ne laser DC high voltage, a He-Ne laser power supply is successfully designed. The He-Ne laser power supply is based on the PWM control chip SG3524, and adopts a constant frequency pulse width modulation control mode to automatically adjust the output power to obtain a stable power output. The flyback transformer driver circuit is reasonable designed. The effective control of the power supply current and the self-stabilization of the current during operation are realized. The current stability of the laser power source and the laser light power stability are tested at current values of 3, 4 and 5 mA. The test results show that the laser power output current and the laser output power are both stable. The power supply has the advantages of simple structure, high efficiency and stability, small size , light weight , which has strong promotion.

It is difficult to ensure perfect alignment of the laser resonator in the process of actural assembly and operation process. Therefore, it is necessary to study the stability of resonator. The "Rigord analysis method" is used to analyze the variation of power extraction efficiency for parabolic mirror off-axis unstable resonator and spherical mirror resonator, when the angle is out of adjustment. The output characteristics of the two types of resonator are discussed, and the stability of the off-axis unstable resonator is studied when the radius of curvature of the resonator mirror increased. The results show that the power extraction efficiency of the parabolic mirror resonator is 5.6% higher than that of the spherical mirror one when mirror tilt angles varied between ―6 mrad to 6 mrad. For parabolic mirror resonator, the power extraction efficiency is 3.5% higher that of the spherical mirror resonator, when the variation of cavity length is in the range of ―1 mm to 1 mm. When the radius of curvature of resonator mirror is increased by 2 mm, the power extraction efficiency of the parabolic mirror resonator is increased and the anti-misalignment characteristics are better.

In order to improve the acceptance temperature bandwidth of laser second harmonic generation, temperature insensitivity of laser second harmonic generation in LiB3O5 (LBO) crystal is proposed by using non-principal plane phase matching method. It is found that when using the LBO crystal for second harmonic generation of 1 064 nm laser, there is a phase matching direction that is not on the principal plane, and the temperature full width at the half maximum (FWHM) in this direction is wider than that in the conventional principal plane direction. In the experiment, the LBO crystal with a cutting angle of (θ＝58.4°, φ＝27.0°) is used for second harmonic generation of 1 064 nm laser, and the temperature FWHM is 76.0 ℃, which is 12 times the temperature FWHM of traditional principal plane phase matching.

It is easy to form micron-level anodic oxide film on the surface of 5083 aluminum alloy, which could significantly affect the afterwards welding quality. Laser cleaning of anodic oxide film on 5083 aluminum alloy surface is studied by using nanosecond fiber laser under the wavelength of 1 064nm. The effects of laser power, scanning speed and pulse width on the laser cleaning effect were studied by using different laser cleaning process parameters. The optimized laser parameters combination was summarized and the corresponding cleaning effect was verified. The results show that there is an optimized combination of laser processing parameters. And the optimized laser power, scanning speed, frequency and pulse width are 42 W, 4 725 mm/s, 250 kHz and 100 ns, respectively. SEM results indicate the anodic oxide film could be fully removed, thus achieving good cleaning effect.

Objective: to assess the clinical efficacy of Er:YAG laser compared with traditional scaling and root planing (SRP) in the treatment of chronic periodontitis (CP) by evidence-based medicine. Methods: Electronic databases including PubMed, EMbase, The Cochrane Library, CNKI, VIP data and Wanfang data were searched to collect literatures which are randomized controlled trials of Er:YAG laser and SRP alone for the treatment of CP from establishment to September 2018. Two researchers independently screened the literature, quality evaluation and data extraction in accordance with inclusion and exclusion criteria, and Revman5.3.3 software was applied for statistical analysis. Results: a total of 11 RCTs were included. The meta results showed no significant difference in periodontal probing depth (PPD) between the Er:YAG laser and the SRP alone［MD＝0.05, 95% CI(-0.01, 0.12), P＝0.12), and clinical attachment loss (CAL), SRP group was superior to Er:YAG laser group ［MD＝0.13, 95% CI(0.02,0.24), P＝0.02］, 3 months after treatment. There was no statistically significant difference between the two groups after 6 months. Conclusion: the existing evidence shows that Er:YAG laser has no obvious therapeutic advantage compared with traditional SRP in short-term and medium-term clinical efficacy.

To investigate the effect of He-Ne laser irradiation combined with antibiotic prophylaxis on postoperative incision healing after cardiac pacemaker implantation. Methods: a total of 146 patients with permanent cardiac pacemaker implantation from March 2013 to October 2018 were randomly divided into Group C (n＝73, antibiotic treatment) and group L (n＝73, He-Ne laser combined with antibiotic treatment). The clinical efficacy, postoperative incision pain, comfort, postoperative infection rate, cystic hematoma rate and incision healing time were observed and compared between the two groups. The complications such as skin peeling and burns were recorded. Results: ①There was no significant difference between the two groups in total efficiency rate and total significant efficiency (P>0.05). ②Postoperative incision pain scores in group L at 2, 3, 5 and 7 days were all lower than those of group C (P0.05), but the healing time of incision in group L was significantly lower than that in group C (P<0.05). ⑤No serious skin burns, blisters or other damage occurred in group L. Conclusion: He-Ne laser irradiation combined with antibiotic prophylaxis can shorten the incision healing time after cardiac pacemaker implantation, reduce the incision pain, improve patient comfort and safety.