This PDF file contains the front matter associated with SPIE Proceedings Volume 7515, including the Title Page, Copyright information, Table of Contents, the Conference Committee listing and the Introduction.

In the paper, taking into account thermal issues caused by the optical absorption of elctro-optic crystal in the high repetition and high average power laser, and establishing the thermodynamic model of electro-optic crystal and using the finite element analysis software for thermodynamic analysis of BBO electro-optic crystals, the temperature distribution is obtained, and the thermal focal length and depolarization loss is calculated.

Now, the processing of natural stone plates is the high performance sawing machine primarily,many researchers deeply studied the processing characters in the sawing process and the strength characters during the processing. In order to realize the profiled-processing and pattern- carving of the natural stone, It lays a solid foundation for the laser cutting and the pattern-carving technology of natural stone plate. The working principle, type and characteristics of laser cutting are briefly described. The paper selects 6 kinds stone plates of natural taken as experimental sample,the experimental sample was China Shanxi Black, Old Spain Golden Yellow, New Spain Golden Yellow, Jazz White, Maple Leaf Red, Cream White respectively. Use high power CO₂ laser cutting system,the stone plates cutting experiment of 6 kinds different hardness, the best working speed are obtained,The experimental results indicate that: The laser cutting speed has no correlation with the ingredient content of stone plate.

As a non-contact cleaning method, laser cleaning can effectively remove particulate contaminations of sizes as small as 0.1 μm without damage to the optics. In this work, 10.6 μm CO₂ laser was utilized to clean the dimethylsilicone oil contaminated on the surface of the gold-coated K9 glass. The dimethylsilicone oil contaminants with different degree were obtained by 10-30 minutes of vapor condensation. Single point irradiation mode was used to study the removal of the dimethylsilicone oil. The cleaning different degree of contaminations was investigated at the variable laser parameters, including laser power, laser frequency, and irradiation time. Optical microscope was used to analyze the cleaning effect. The results show that CO₂ laser can effectively remove the dimethylsilicone oil. On the premise that the gold-coated K9 glasses are not damaged, the cleaning area increases with the increase of radiation time and laser power. The cleaning area doesn't change much with the variation of laser frequency when the other parameters are the same. In addition, at the same laser parameters, the cleaning area increases as contamination degree increases.

A switching power control system of fast axial flow CO₂ lasers based on DSP is presented. The key techniques are described in detail, include the control principle, realization method and program design. The experiment showed that the system make the laser discharge stably and work in multi-mode. The discharge current can be adjusted from 3mA to 85mA continuously. 20-2000Hz frequency, 0-100% duty cycle laser pulse is achieved. The power supply can improve the processing efficiency and quality.

Laser curing is a new application which has distinct advantages compared with traditional curing methods. In this paper we shall present a curing machine based on diode lasers and 25 channels were achieved which means as much as 25 curing points can be realized simultaneously during a short period.

Increasing the output power of the fast axial flow CO₂ laser requires a proportional growth of the mass flow with the laser power for convective cooling of the active laser medium. The previous research on high power CO₂ laser was mostly focused on gas discharge. However, little attention was focused on the gas circulation system, which is also an essential technology to ensure the long time stable work of the high power fast axial flow CO₂ laser. Based on the analysis of the characteristics of the 7 KW fast axial flow CO₂ laser, expounded the important role of the gas circulation system, and then analyzed the parameters, the structure and the design of the system. After that, this paper compared various types of blowers and heat exchangers, chose magnetic levitation radial turbine blower and rectangle finned heat exchanger, in light of the prominent performance and compact structure. Further more, this paper also supplied the methods of the blower and heat exchanger selection and design. The results indicate that the magnetic levitation radial turbine blower and rectangle finned heat exchanger which have been chosen are suitable to the 7 kW fast axial flow CO₂ laser.

Diode laser has been used with side-pumped in the solid-state laser for gaining high output laser power. But the beam quality of the output laser, and the M² factor is more than 20. The high power diode end-pumped laser of LYPE can overcome the shortcoming of the above, can get high output power and good beam quality. With 25W end-pumped, We had gotten the 13 W output power at 1064nm, and 6W at 532nm, and 2.5W at 355nm, and 1.2W at 266nm; By 40W pumped, gotten 20W at 1064nm. And the pulse repetition frequency is from 1 kHz to 100 kHz, and the output mode is TEM00, and M² is less than 1.5.

This paper first describes the characteristics and the transmission characteristics of laser, and analyzes the theory that charge-coupled device (CCD) takes out the information charge from the charge packet by the scanning order to make the received images reproduce as the electrical signal form. On this basis, an on-line thickness measurement system is designed with a laser, a diaphragm, a filter, lenses, a charge coupling device (CCD), a splitting prism and other components. The system has several functions, such as dust-proof, shock-proof, anti-high and anti-low temperature, anti-electromagnetic interference, and so on; the measurement range is wide, the measurement accuracy is high and the dynamic tracking speed is fast, etc. With this system, the length, the width and the thickness of the steel plate can be measured real-time. At last this paper analyzes and discusses the system error with the real examples, and gives a few important conclusions.

It is very important for testing of temperature field in laser processing. A new CCD camera based on DSP for measurement of temperature field in laser molten pool is presented in this paper. It uses a DSP as the main CPU without the computer to process images. In this way, the system is simple and efficient. It can not only display 2D morphology and gradient images of temperature field, but also give numerical distribution of temperature field. Comparing with PC-based system, DSP-based system has a small and integrated size, measuring temperature in real time and quickly processing images. After further developing, the system based on DSP could be an useful device in laser processing.

In this paper the beam characteristics of off-axis negative branch confocal strip unstable resonator have been studied. The resonator geometric relation is derived, and the formulas of mirror geometric parameters are expressed. Numerical simulation has also been carried out for negative branch strip off-axis confocal unstable resonator by means of Fox-Li iteration method and Collins Formula. The result shows that the intensity at the optic axial is stronger than other region and the phase distribution is close to uniform distribution on the output mirror, the far field intensity angle distribution is a typical Gaussian distribution of fundamental mode with little side lobe because of the straight edge diffraction. The influence of tilted mirror with different angle on far-field light intensity distribution for both negative and positive branch also have been compared, which shows that negative-branch is far less sensitive to the misalignment of mirror than positive branch.

An 81 MHz TEM electromagnetic wave transmitting between the electrodes would cause the nonuniform discharge along the electrodes. The variation of the voltage distribution with pressure and feed-in power bring difficulties to design match network. In order to achieve impedance matching, the 2000W RF slab discharge platform the different type of matching network are used. Through analyzing the matching network, the equivalent electrical parameter is estimated. In the experiment, though using resonance inductances the voltage distribution along the electrodes is improved. The results show that under the typical condition of the RF slab laser operation, the π matching network can work well and the reflective power is less than 5%. When a mid-feed point is used, the feed-in power is 2000W, two 28nH inductances are attached at both end of the electrodes, two 24nH inductances are fixed on both points of one-fourth of the electrodes, the uniform discharge is got on the 500mmx40mm electrodes, and the feed-in power density is 65W/cm³.

University Paris XI has developed a facility, which called LASERIX, intended to realize and use for applications transient collisional X-ray laser (XRL) beamlines at various wavelengths. It is based on the effect caused by beamlines of the ultra-intense infrared laser (100TW) rip into the high-density and high-temperature plasma, providing XUV laser pulses at alterable wavelengths of 7-40nm This soft-X laser source is widely used in biology, bio-medical, solid physics, plasma physics and many other domains. In order to make LASERIX a stable XUV laser source, the stable infrared beams are neededThe stability of the beams enhances the energy of X laser pulses. A system of detecting temperatures in different points of the laser chain and monitoring laser beam has been developed. For the second step, a new compressor has been built to produce auxiliary infrared laser beam which helps to improve the XUV pulse's energy. This article elaborates on the design and installation of them with the results discussed.

Laser marking has been found wide application in many fields. However, laser colorful marking has seldom been used because of its complexity of processing. Recently, the researchers have been attracted on this research for its' huge potential market. Nevertheless, the mechanism of laser colorful marking is still not quite clear. In order to explore essence of laser colorful marking on metal, this paper introduces the mechanism of laser colorful marking on stainless steel and titanium and the mechanism of color generation of film processed by laser colorful marking. The mechanism of laser colorful marking on metal is the optical films which are oxide and nitride coated on the surface of metal, are generated by controlling laser energy input and the approach of scanning region. It was found that the films on surface of stainless steel contain ferric oxides and nitrides and the films on surface of titanium contain titanium oxides and nitrides. The composition of films with different color is different in terms of substance.

For its unique advantages including compact architecture, small volume, light weight, less thermal effect, high conversion efficiency, excellent beam quality, etc., high power fiber laser booms since 1990s and has been used in many fields, especially in material processing, such as marking, cutting, scribing, drilling and texturing, etc. As a new solid-state laser, more and more fiber lasers are employed in laser processing in china nowadays, but most of them are produced by IPG and SPI. In the last decade, many efforts have been done for fiber laser in some domestic universities and institutes, such as Nankai University, Tsinghua University and Shanghai institute of optics & fine mechanics, but no mature product of fiber laser has been brought out until now. To achieve high power all fiber lasers, many key technologies should to be solved.

Ship is easy to rust because of its special working condition. Removal of the rust from the ship surface is generally required for maintaining ship. The feasibility of removing rust using pulsed laser has been confirmed by the past researches. However, the general utilized laser, e.g., pulsed Nd: YAG laser with narrow pulse duration and high peak power, suffers very low average power and throughput. TEA CO₂ laser, which also has narrow pulse duration and high peak power, is expected to obtain high throughout because it is easy to obtain high average power. This paper investigated the feasibility and the efficiency of removal of rust from the ship steel using TEA CO₂ pulsed laser. The results show that TEA CO₂ pulsed laser can effectively clean the rust by using suitable parameters without damage the substrate. A cleaning threshold for stripping rust of power density exists. Also, the effect of the process parameters on the efficiency and performance as well as the removal mechanism were studied in this paper.

Periodic nonlinearity is the main limitation on the accuracy of the nano-displacement measurements in the heterodyne interferometers. It is mainly produced by non-ideal polarized beams of the leaser and imperfect alignment of the optical components. In this paper, we model the periodic nonlinearity resulting from non-orthogonality and ellipticity of the laser beam by using combination of neural networks such as stacked generalization method and mixture of experts. The ensemble neural networks used for nonlinearity modeling are compared with single neural networks such as multi layer percepterons and radial basis function.

Photodynamic therapy (PDT) treatment is a new treatment for tumour and Dermatology. With the successful development of the second-generation photosensitizer and the significant manifestations in clinics, PDT has shown a more extensive application potentials. To activate the photosensitizer, in this paper, we present a GaAs-based diode laser system with a wavelength of 635 nm. In this system, to prolong the working life-time of the diode lasers, we use specific feedback algorithm to control the current and the temperature of the diode laser with high precision. The clinic results show an excellent effect in the treatment of Condyloma combined with 5-ALA.

Societal pressure to renewable clean energy is increasing which is expected to be used as part of an overall strategy to address global warming and oil crisis. Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by government, of which the costs and prices lower continuously. The next generation thin-film devices are considered to be more efficiency and greatly reduced silicon consumption, resulting in dramatically lower per unit fabrication costs. A key aspect of these devices is patterning large panels to create a monolithic array of series-interconnected cells to form a low current, high voltage module. This patterning is accomplished in three critical scribing processes called P1, P2, and P3. All-solid-state Q-switched lasers are the technology of choice for these processes, due to their advantages of compact configuration, high peak-value power, high repeat rate, excellent beam quality and stability, delivering the desired combination of high throughput and narrow, clean scribes. The end pumped all-solid-state lasers could achieve 1064nm IR resources with pulse width of nanoseconds adopting acoustic-optics Q-switch, shorter than 20ns. The repeat rate is up to 100kHz and the beam quality is close to diffraction limit. Based on this, 532nm green lasers, 355nm UV lasers and 266nm DUV lasers could be carried out through nonlinear frequency conversion. Different wave length lasers are chose to process selective materials. For example, 8-15 W IR lasers are used to scribe the TCO film (P1); 1-5 W green lasers are suitable for scribing the active semiconductor layers (P2) and the back contact layers (P3). Our company, Wuhan Lingyun Photo-electronic System Co. Ltd, has developed 20W IR and 5W green end-pumped Q-switched all-solid-state lasers for thin-film solar industry. Operating in high repeat rates, the speed of processing is up to 2.0 m/s.

Dispersion equations of bulk modes in a rectangular waveguide of semiconductor metamaterial are derived by a modified "Marcatili method". The existence conditions for bulk modes are discussed, and the Brillouin diagrams of different bulk modes and the lowest TM bulk mode in different waveguides are drawn. They demonstrate that different heights correspond to different guidance frequency ranges which have no superposition with each other and a waveguide with larger height possesses wider pass band of light. In addition, tendencies of degeneracy for different modes are observed. These properties are of particular relevance to devices requiring band-pass or single-mode propagation. Then a rectangular resonant cavity with different anisotropic parameters is designed and investigated, which is filled partially with a right-handed semiconductor metamaterial (RHSM) and partially with a left-handed semiconductor metamaterial (LHSM). The resonant mode solutions of the general case of the 3-D rectangular resonator cavity filled with non-dispersive RHSM and dispersive LHSM are explored by use of a graphical method. It is demonstrated that the resonant modes in such a resonator cavity are closely dependent on the spatial dispersion relation of the semiconductor metamaterial. The resonant cavity including three subcases of different combinations of real and imaginary propagation constants of the two regions is discussed. This novel 3-D semiconductor metamaterial brings a new method to construct rectangular resonant cavities and provides more design flexibility and tolerance.

A numerical model of the folded resonator is founded by using the eigenvector method. The beam characteristics and relative amplitude distribution of dominant mode of the N-shaped three-folded resonator with different aperture diameter are obtained by numerical simulation. The experiment of the resonator is done on HUST5000 high power transverse flow CO₂ laser. The results show that the mode volume of the N-shaped three-folded resonator with the aperture diameter of 25mm can match the gain zone of the transverse flow CO₂ laser well, the output power and beam mode are fit for industrial applications. The laser welding system based on this resonator is developed for gas generator of automobile safety airbag.

Microchannels are fabricated into transparent materials usually have two different methods, the first method is using tight focused femtosecond laser processing and chemical etching, and in the other method, many laser-produced voids are linked together to form a hollow channel, whereas both methods of channel fabrication is relatively slow, a novel method of parallel processing channels have been demonstrated based on the self-focusing formation theory. In addition, It provides a theoretical basis for the further study on the microchannel fabricating of femtosecond laser.

Aiming to the accuracy output laser power control of RF excited CO2 laser. A pulse width laser power modulating unit and corresponding experiments was studied. Hardware circuit based on TMS320F2812 microprocessor and software program based on CCS3.1 platform was designed. On condition of given working mode of the laser and laser power, when real laser power was detected as the feedback, appropriate ignition pulse, maintenance pulse, continuous working mode modulating pulse, pulse working mode modulating pulse was given to realize a loop control system for laser power. When the pulse width modulator was used to modulate the laser power, the modulating frequency can be modulated in the range of 5 Hz~5 KHz if the laser was working in pulse mode. And the laser power can be modulated in the range of 5%~95% of the maximum value at any mode with the fluctuate accuracy within ±2%.

In this paper, three-dimensional cutting test of auto-body panel was carried out by CO₂ laser on the five-axis linkage numerical control cutting machine. First, the advantage of adopting 3D laser cutting method to process Auto-body Panel was summarized, and the essential factor in cutting quality was discussed. Then, the technical difficulty in three-dimensional laser cutting was addressed, and several experiments and theory analysis on problems such as collision and overburning at upslope, downslope, and corner were conducted, with corresponding improvement methods and solutions proposed. Finally, the cutting quality was evaluated with respect to kerf width, surface roughness, and the size of heat affected zone (HAZ). The experimental results indicated that to obtain three dimensional cutting workpiece with superior cutting quality and high cutting precision, the incident angle changed with the pose of cutting head should be limited to 20°. Narrow kerf (0.28~0.50mm), smooth surface (2.68μm~7.22μm) and small heat affected zone (appr. 70μm) can be obtained under the condition of appropriate technological parameters. Besides, overburning can be eliminated effectively at upslope, downslope and corner by decreasing laser power, adopting pulse laser, or using the air as assisting gas alternatively.

The conditions that the droplet's thermodynamic parameters change with time have been calculated, and the contrast between them when different laser pulse patterns are selected have been analyzed accordingly. The results show that: Two atomization processes are formed, and the second one is not evident for the case of gaussian distribution laser pulse. The change trend of the time-related expansion velocity is first increased, then decreased for the case of flat top distribution laser pulse, and is first increased, then maintained for the case of gaussian distribution laser pulse. The expansion process displays a stable stage in which the expansion velocity fluctuates slightly after atomization for the case of gaussian distribution laser pulse. In the terminal phase of the laser pulse, negative expansion acceleration appears for the case of flat top distribution laser pulse. The time-related temperature variations are more complicated for the case of flat top distribution laser pulse.

In order to achieve the Omni-directional detection and be compatible with the forward intercept warhead to have a good damage effect to the anti-ship missile with a certain distance, so the double laser beam forward detection techniques for the anti-missile of the medium-caliber naval guns was given. The theory of this technique is that translating the speed variable into time variable to identify the target conditions, this method can simplify the design of the software. Due to the size restrictions, a special biconical reflector with two different forward angles was designed to make double laser beams. The receive system was divided into two parts to solve the receive problem of the reflection signals. This technique can exclude the interference of the ocean waves and own projectiles effectively, so the sea-skimming flying reliability is increased.

A novel approach Laser Ablation Combined with Chemical Flow Etching is proposed. How laser pluses energy density, repetition rate, pulse width, scan velocity and other parameters cause the eclipsed quantity and the surface quality by combining etching method on metal materials is studied by using experiments. Moreover the effects of corrosive style, its concentration and rushing velocity and other flow parameters are also analyzed in combining process. Experimental results show that the new approach is inspiring in enhancing surface quality and machining velocity. It is obvious that the liquid is the important factor of reducing lags and roughness, also of increasing eclipsing quantity.

In the area of Laser marking, the general control method is insert control card to computer's mother board, it can not support hot swap, it is difficult to assemble or it. Moreover, the one marking system must to equip one computer. In the system marking, the computer can not to do the other things except to transmit marking digital information. Otherwise it can affect marking precision. Based on traditional control methods existed some problems, introduced marking graphic editing and digital processing by the computer finish, high-speed digital signal processor (DSP) control marking the whole process. The laser marking controller is mainly contain DSP2812, digital memorizer, DAC (digital analog converting) transform unit circuit, USB interface control circuit, man-machine interface circuit, and other logic control circuit. Download the marking information which is processed by computer to U disk, DSP read the information by USB interface on time, then processing it, adopt the DSP inter timer control the marking time sequence, output the scanner control signal by D/A parts. Apply the technology can realize marking offline, thereby reduce the product cost, increase the product efficiency. The system have good effect in actual unit markings, the marking speed is more quickly than PCI control card to 20 percent. It has application value in practicality.

Laser keyhole welding process is not well understood because the related physics are too complex. Numerical simulation of transient keyhole evolution provides fundamental data needed to improve understanding of the mechanisms of porosity formation during laser welding. In this paper, a three dimensional mathematical model was proposed to simulate the keyhole formation process of laser welding. The coupled effects of multi-reflections Fresnel absorption of keyhole, heat conduction, heat convection, heat radiation and Knudsen jump boundary conditions on the liquid-vapor evaporation interface were considered in this model. A level set method and a fast sweeping method were developed to solve the model. The transient keyhole shape, the surface recession speed due to evaporation and the thermal distribution of keyhole wall were investigated. The time-varied surface tension force of keyhole wall was also calculated.