Japan Long-Term Research Visit: Picosecond Time-Resolved Spectroscopy of Laser Plumes

该奖项将支持伊利诺伊大学厄巴纳-香槟分校机械与工业工程系M. Quinn Brewster教授对日本进行为期9个月的长期访问，与工业科学技术机构机械工程实验室（MEL）的Yukio Yamada教授进行合作研究项目。国际贸易和工业部。这项研究将包括对激光羽流皮秒时间分辨光谱的研究。与激光材料加工相关的一个主要问题是实现激光能量到工作场所的有效耦合。这种耦合是由激光与材料相互作用产生的羽流/等离子体/激波中目标表面和目标表面上复杂的非线性机制控制的。各种研究表明，与羽流形成有关的透过率和/或热耦合系数急剧下降。羽流的特征在很大程度上是未知的，但已知取决于入射激光通量水平。这项研究解决了在高功率激光照射下铝靶上形成的羽流的结构和传热机制的难题。这项研究支持了一项由美国国家科学基金会赞助的研究，该研究的主要目标是开发技术，用于确定激光能量耦合到金属目标时羽流吸收、散射和发射的相对重要性。研究结果具有优化和扩大激光在材料加工中的应用的潜力。MEL的设备是最先进的，包括高功率处理激光器，快速扫描光谱仪，皮秒，脉冲染料激光器和光示波器。这种设备在世界上只有少数实验室才有。现代实验设施和应用皮秒时间分辨光谱学的经验的结合，日本东道主研究员和高功率激光与材料相互作用的经验，美国首席研究员的一部分提供了一个独特的机会，以扩大对美国至关重要的技术的知识库工业的竞争力。

This award will support a long-term visit of nine months by Professor M. Quinn Brewster, Department of Mechanical and Industrial Engineering, University of Illinois at Urbana- Champaign, to Japan for a cooperative research project with Professor Yukio Yamada at the Mechanical Engineering Laboratory (MEL), Agency for Industrial Science and Technology, Ministry of International Trade and Industry. The research will include a study of the picosecond time-resolved spectroscopy of laser plumes. A major problem associated with laser material processing is achieving efficient coupling of laser energy into the workplace. This coupling is governed by complicated, non- linear mechanisms at the target and above the target surface in a plume/plasma/shock wave generated by laser-material interaction. Various studies have shown sharp decreases in the transmissivity and/or thermal coupling coefficients associated with plume formation. Characteristics of the plume are largely unknown, but are known to depend upon incident laser flux level. This research addresses the difficult problem of shedding more light on the structure of, and heat transfer mechanisms in, the plume formed above Al targets when irradiated by high power lasers. This research supports a companion NSF-sponsored study which has as a primary objective the development of techniques which can be used to determine the relative importance of plume absorption, scattering, and emission on coupling of laser energy into metal targets. Results of the research have the potential of optimizing and expanding the use of lasers in materials processing. The facilities at MEL are state-of-the-art and include high power processing lasers, rapid scan spectrometers, and picosecond, pulsed dye lasers and photo-oscilloscopes. This type of equipment is found in only a few laboratories in the world. The combination of modern experimental facilities and experience in application of picosecond time-resolved spectroscopy on the part of the Japanese host researcher and experience in high-power laser-material interaction on the part of the U.S. principal investigator offers a unique opportunity to expand the knowledge- base of a technology which is of critical importance to U.S. industrial competitiveness.