This thesis uses liquid-phase femtosecond laser processing of zinc flakes in anhydrous ethanol. The results show that a micro-nano composite structure is formed; and the period of the composite structure is increased nearly 10 times compared with that fabricated in air. The direction of period structure is distributed at an acute angle to the processing direction and not directly related to the polarization direction. The formation direction of the micro-pores is the same as that of the vortex flow in the liquid.
Femtosecond laser was used to fabricate antireflective holes on the surface of ZnS. The micro hole structures were formed by different single laser pulse energy. It was found that with the increase of single pulse energy, the infrared transmittance of ZnS surface decreased. Under optimal parameters (single pulse energy of 0.1 μJ), the average infrared transmittance of ZnS increased to over 79%, 4% improvement compared to the untreated ZnS. The light transmission in planar ZnS and micro hole structures ZnS was simulated by FDTD, which theoretically verified the antireflection property of micro hole structures.
Digital medical 3D printing technology is a new hi-tech which combines traditional medical and digital design, computer science, bio technology and 3D print technology. At the present time there are four levels application: The printed 3D model is the first and simple application. The surgery makes use of the model to plan the processing before operation. The second is customized operation tools such as implant guide. It helps doctor to operate with special tools rather than the normal medical tools. The third level application of 3D printing in medical area is to print artificial bones or teeth to implant into human body. The big challenge is the fourth level which is to print organs with 3D printing technology. In this paper we introduced an application of 3D printing technology in tumor operation. We use 3D printing to print guide for invasion operation. Puncture needles were guided by printed guide in face tumors operation. It is concluded that this new type guide is dominantly advantageous.
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.
Selective laser sintering (SLS) technology which is based on additive material shows great advantages for its'
almost no limitation in sintering material. Beside additive fabrication traditional laser processing technologies such
as laser cuttinglaser drillinglaser marking are based on removing material. In this paper laser vaporizing sintering (LVS) fabrication technology has been introduced to fabricate thin wall structure. This technology is based on both material removal by laser vaporizing and material addition by laser sintering. This is a novel technology which combines two different methods to fabricate micro part. This method can sinter several powder particles together to form microstructure. It can be used to fabricate 2.5 dimension thin wall parts and hopefully will be developed to a new material removing-adding technology to produce micro-components.
In Selective Laser Micro Sintering the powder particles should be assembled or arranged and
sintered together. Optical tweezers make used of optical refractive force to manipulate micro objects.
Currently the manipulated objects are limited to nano or several micro meters scale. In this paper we develop
a novel optical tweezers which employs pulse laser force to drive bigger particles and assemble them. This
pulse laser is controlled to form spiral trap which can grasp big particles. In our experiment the 50μm-
100μm-diameter metal particles were moved on a solid surfaces in a process we call 'laser spiral driving
force'. Nearly any shape particle, including sphere and non-regular shape, can be moved on the surfaces.
In laser sintering we adopt the method of Nd: YAG frequency doubling to acquire short wave laser in order to obtain fine focus. The paper describes and discusses the method as well as the beam quality of the laser. Based on experiments and theories, we studied frequency doubling in a KTP crystal on Nd:YAG laser by the resonant external ring cavity. The Nd:YAG laser average power is 50w with Q-switch and its frequency is 1005Hz. In the experiment the wavelength of 0.532μm green light output was obtained with 31.4% light conversion efficiency when 1.064μm input average power is 35w. In the green light the proportion of TEM00 model is about 95%. The method is proved to be an effective way to solve the problem of how to get a mini-focus. It is especially useful in the application of laser rapid prototyping. The experimental results for the characteristics of ring cavity frequency doubling were analyzed. The two lasers of 1.064μm and 0.532μm on the beam quality were compared in this paper. The thesis provides the pictures of beam focuses tested with CCD and compares some experimental results with those pictures. A theory of the ring cavity frequency doubling has been put forward in this paper. The sintering effect of the 0.532μm laser was showed in contrast with the 1.064μm laser. The experimental results show that the short wave laser is better for the micro fabrication.
Many factors influence laser cutting quality. In this paper, the influence of laser head movement on 3D laser cutting is investigated. Except normal movement which laser head is vertical to work piece surface, three types of movement defined in 3D laser cutting are considered. Experimental design method is used to analyse cutting result. In order to quantitatively describe the relationship between cutting quality and cutting parameters, artificial neural network (ANN) has been setup. The quality marks system is used to evaluate cutting result. The test shows the calculated quality points by ANN is very similar with actual cutting result. The laser head forward movement is better than the others. The ANN is very useful to optimize cutting parameters, predict cutting result and deduce new information.
There are many micro-fabrication technologies. Some micro-components can be fabricated by selective laser sintering (SLS). When selective laser sintering metal powders is used to produce micro-components, there are numbers of factors which will influence final result, such as laser wavelength, laser power, diameter of laser beam, scanning speed, particle size and materials etc. These factors are not single but interfere with each other. The change of one factor will greatly affect the character of final micro-components (such as width of scanning track , dimension error, component hardness ,etc). In selective laser sintering metal powders, many experiments are needed in order to get the optimum process parameters. However, this will cost much time and money. Moreover in later process, new experiments will be needed in order to get the optimum process parameters due to the change of one factor. Many models about selective laser sintering metal powders have been investigated in the past. Nevertheless, these models are about the interaction of laser and metal powders, and the physical and thermal response to the initial condition. They are provided for the macro-fabrication. No model can be applied in the micro-domain, and no one aims at the influence of these factors on the character of the final micro-component. In this paper a numerical model about the relation of these factors and the character of final micro-components is provided to minimize the number of experiments. This model will include the major factors of SLS in micro-domain, and through such a model we can deduce the numerical value of optimum process parameters from final micro-component character instead of making a lot of process experiments. Therefore the cost of micro-fabrication with SLS techniques will be greatly reduced.
As laser microfabrication develops fast more and more micro parts of MEMS are produced with laser micro processing technology. Excimer laser ablation is a versatile tool for the micro machining of various materials. Excimer laser materials processing, which is performed in most cases using a mask projection system forms a 3D shape by ablation material. Recently a large number of articles about polymer ablation with excimer lasers have appeared. However the powder material especially metallic powder is paid little attention in excimer laser micro machining. In this paper several types of powder material are investigated in excimer laser ablation. The ablation rate of different powder materials with various fluence ranges, wavelengths, and pulse lengths are studied in experiment. The parameters of excimer laser were optimized to fabricate a micro part. The diameter of about 100 micron gear made of nano powder was finally produced with a mask project system using nanopowder. This method is more efficient than laser writing with a focal spot.
Selective laser sintering (SLS) is a process that uses a rastering laser to sinter powder particles into a computer defined shape. In order to fabricate micro part with laser sintering the laser beam spot should be focused smaller, on the other hand the size of sintered powder particles should be smaller too. Therefore Nd:YAG laser doubling frequency is used to obtain mini-focus. Based on theories of nonlinear and resonant cavity, an equipment which perform frequency doubling on YAG laser(1.06μm) by the external resonant ring cavity has been designed. With the equipment the wave length of 0.532μm green light was output. The focused laser spot of 15μm diameter was obtained with 10W power. Meanwhile the micron metal powder was used in selective laser micro sintering (SLMS). The behavior of laser sintering different metal powder was investigated. Finally the micro Chinese characters which is small as a tip of match made with laser selective micro sintering micron metal powder are shown.
In this paper two common 3D flexible processing methods using high power laser are introduced. One is high power YAG laser robot which use fiber to propagate laser beam. The robot holds laser head to move along spatial route on the surface of 3D part. The movement of robot influences laser processing result. Another is CO2 laser multi-axis system which uses mirrors to transfer laser beam. The quality of laser beam has great effect on propagation of laser beam and therefore influences laser processing quality. In these systems the programming is key to process 3D part. Currently the low efficient on-line teach-in programming is mainly used in these systems. Authors introduce their own developed high efficient off-line auto programming software for 3D laser processing---LaserCAM. The LaserCAM software in auto manufacture in China has been successfully applied.
In this paper two common 3D flexible processing methods using high power laser are introduced. One is high power YAG laser robot which use fiber to propagate laser beam. The robot holds laser head to move along spatial route on the surface of 3D part. The movement of robot influences laser processing result. Another is CO2 laser multi-axis system which uses mirrors to transfer laser beam. The quality of laser beam has great effect on propagation of laser beam and therefore influences laser processing quality. In these systems the programming is key to process 3D part. Currently the low efficient on-line teach-in programming is mainly used in these systems. Authors introduce their own developed high efficient off-line auto programming software for 3D laser processing---LaserCAM. The LaserCAM software in auto manufacture in China has been successfully applied.
The laser micro-fabrication technology for micromachine is a noticeable research direction in micro-machine manufacture. In this paper several laser micro-fabrication technologies have been introduced. They are laser mask project lithograph, focus laser beam etching, selective laser sintering rapid fabrication and laser direct deposited fused powder. Authors also introduce the micro gears made with excimer laser mask exposure lithograph in PMMA and the micro Chinese character which is as small as a tip of match made with powder laser sintering technology. Furthermore authors propose another way to make micro-part which use fiber laser or disk laser combined with nano powder.
This paper briefly introduce our work on new biochip manufacuring utilizing excimer laser micromachining. The experiment results shows, that this technology have potentials in actual microstructure forming, processing way, manufacturing cost, efficiency, etc. We investigate the projection mask ablation on PMMA, and get the microgear sample. With the relative motion between the workpiece and the mask, the repeated excimer laser pulse will etch a 3D microstructures, or even form several different profiles on the straight line microgroove. This will be very useful for the microchannel formation on Biochip.
For gas laser, working gases in resonator have two interaction with laser. One is to generate excited radiation, the other is to affect the propagation of the laser beam. For the latter, gas thermal lens has great effect on laser beam in the resonator for high-power CO2 laser because of long resonator and high laser power in resonator. In this paper, a physical model for gas thermal lens is proposed. As well as the influence of thermal lens upon the propagation of the laser beam in the resonator according to this model is analyzed. It is found that gas thermal lens will transform the laser beam acting as a negative lens which is at the middle of the resonator since the symmetry of the resonator. This negative lens will transform the beam waist position and radius to deviate the idea beam waist position and radius which are determined by the passive resonator. And this deviation causes the mismatch of the transformed laser beam with the resonator. Further more this mismatch results in the energy couple of TEM00 beams to the higher ones to form the mix-mode laser beam and decreasing laser beam quality. In the paper the effects of the laser power, on laser beam modes are analyzed. And as an example, the laser output mode of a high-power CO2 laser with radio-frequency excited and fast-axis-gas-flow is calculated from the above theory. Meanwhile, the output mode of this type of laser is measured by high-power laser beam analyzer - laserscope UFF100. And the calculation is accord with the measurement. So for high-power C02 laser, the gas thermal lens is an important reason which influence the output mode ofthe laser beam.
In this paper, the theory of 3D laser welding and cutting was established firstly. Then the expert system for 3D laser processing and software of 3D laser processing CAD/CAM were developed, respectively. Under the guidance of these software, with high power CO2 laser, the 3D covers of a car have been cut and edge smoothed, which decrease the number of models and shorten the period of production. With adoption of this technology, the covers of extended Hong Qi cars and furthermore Da Hong Qi cars have been processed successfully, which will bring out the innovation of production design and the revolution of processing technology in manufacture industry.
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