Zuo Tie-chuan

Laser microfabrication with metallic powder

Rapid prototyping (RP) technology has developed fast in the last year. It is an inevitable trend to adopt laser melting metal powder material directly to make metal parts from RP technology to rapid manufacturing. However, at present it is still at the stage of explorlation to utilize micro powder metal material for microfabrication. In this article two methods of microfabrication were investigated. One is selective laser microsintering. Equipment of YAG doubling frequency laser was used to sinter metallis powder materials to fabricate the micro part. Another is microladding fabrication. With special designation of a powder feeder the fused deposition of metallic powder was conducted. The impact factors such as laser parameters, processing parameters on microfabrication, were analyzed. Through optimization in the parameters, a micrometal part has been successfully fabricated.

Analysis of X-Ray Photoelectron Spectroscopy of Polymethyl Methacrylate Etched by a KrF Excimer Laser

The C 1s and O 1s electrons in polymethyl methacrylate etched by different incident laser intensities are analysed by x-ray photoelectron spectroscopy. The results show that when the incident laser fluence increases gradually, the percentage of carbon atoms in C–C bonds decreases while the one in carbonyl group (C=O) and alkoxy group (C–O) increases, and the percentage of oxygen atoms in C=O bonds increases while the one in C–O bonds decreases. Based on the analysis of the chemical structure, the energy level transition, energy diversion, and dissociation of bonds are theoretically examined, which is consistent with the experimental results.

The development of laser microprocessing in China

In 1995 the National Center of Laser Technology (NCLT) of China was opened. From that time there has been research on laser microfabrication at NCLT. Under the support of the National Science Foundation and Beijing Science Foundation several projects involving laser micro processing have been carried out. NCLT has make great progress in the field of laser micro processing with excimer laser and powder microsintering using YAG laser. Based on the principle of excimer laser micromachining, a micromachining system, including a beam delivery system, mask illumination system based on fly’s eye homogenizer, double telecentric optical and electrical system, has been developed. The application of micromachining technology to the fabrication of MEMS has been conducted and 50∼500µm diameter micro-gears have been made using polymers and ceramics. Meanwhile the excimer laser has been to manufacture microfluid biochip. Besides this the microfabrication using laser sintering powder material has been investigated at NCLT. This represents the one aspect of the development of laser microprocessing in China.In 1995 the National Center of Laser Technology (NCLT) of China was opened. From that time there has been research on laser microfabrication at NCLT. Under the support of the National Science Foundation and Beijing Science Foundation several projects involving laser micro processing have been carried out. NCLT has make great progress in the field of laser micro processing with excimer laser and powder microsintering using YAG laser. Based on the principle of excimer laser micromachining, a micromachining system, including a beam delivery system, mask illumination system based on fly’s eye homogenizer, double telecentric optical and electrical system, has been developed. The application of micromachining technology to the fabrication of MEMS has been conducted and 50∼500µm diameter micro-gears have been made using polymers and ceramics. Meanwhile the excimer laser has been to manufacture microfluid biochip. Besides this the microfabrication using laser sintering powder material has been investigated at NCL...

Three-Rod Resonator for Krypton Lamp Pumped 1.8 kW Continuous-Wave Nd:YAG Laser

A three-rod series resonator cw Nd:YAG laser suitable for the industrial applications is presented. The symmetrical resonator laser has been developed and is rated at 1820-W output power with beam parameter product 24 mm.mrad. By utilizing the symmetrical resonator design, the characteristic of beam with multi-rod is not obviously decreased compared with that of a single one. The system total electro-optics efficiency of lamp pumped YAG crystal is as high as 4.0%. The main factors, which affect output power and beam quality of high power solid-state laser module, are theoretically analysed.

The investigation on laser microfabrication with metallic powder

Rapid Prototyping (RP) technology develops fast recent year. It is an inevitable trend to adopt laser melting metal powder material directly to make metal part from RP technology to RM (Rapid Manufacturing). However at present it is still at the stage of exploring to utilize micro powder metal material for micro-fabrication. In this paper two methods of microfabrication were investigated. One is selective laser micro sintering. Equipment of YAG doubling frequency laser was used to sinter metallic powder materials to fabricate micro part. Another is microcladding fabrication. With special designation of powder feeder the fused deposition of metallic powder was conducted. The impact factors such as laser parameters, processing parameters on micro fabrication were analyzed. Through optimization in the parameters, a micro metal part has been successfully fabricated.Rapid Prototyping (RP) technology develops fast recent year. It is an inevitable trend to adopt laser melting metal powder material directly to make metal part from RP technology to RM (Rapid Manufacturing). However at present it is still at the stage of exploring to utilize micro powder metal material for micro-fabrication. In this paper two methods of microfabrication were investigated. One is selective laser micro sintering. Equipment of YAG doubling frequency laser was used to sinter metallic powder materials to fabricate micro part. Another is microcladding fabrication. With special designation of powder feeder the fused deposition of metallic powder was conducted. The impact factors such as laser parameters, processing parameters on micro fabrication were analyzed. Through optimization in the parameters, a micro metal part has been successfully fabricated.

Stimulated Emission of Gamma Photon from Ultrashort Pulse Intense Laser-Solid-Target Interaction*

The efficient production of energetic gamma photons is a significant physical process in the relativistic ultrashort pulse laser-plasma inducing photonuclear action. Based on the interaction of laser-solid-target, an analytical theory on stimulated gamma photon emission from a hot electron Bring the target-nucleus is developed by a relativistic full quantum method. The emitting power or probability of gamma photon in arbitrary space direction can be calculated for laser irradiating solid-target normally. It is valid only if the scatter-centre is immovable or its motion can be neglected compared with that of the scattered electrons.