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Investigation of the interactions between femto-second pulse laser and ultrapure water

飞秒脉冲激光与超纯水相互作用的研究

基本信息

批准号：
20246037
负责人：
SAITO Takayuki
金额：
$ 31.62万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2010
项目状态：
已结题

项目摘要

Femtosecond-pulse lasers (fs pulses) cause very interesting phenomena due to their extremely high energy density. The effects on substances are not thermal, but multi-photon absorption. When this multi-photon absorption of fs pulses operates on water, extraordinary phenomena different from laser-induced cavitation by a usual laser such as a nano-pulse laser are induced. In the present investigation, fs pulses of 50-150fs in duration, 1kHz in repetition rate and 0.2-1.4μJ in pulse energy were focused at ultrapure water in a glass cell through several types of lens. The fs pulses split from original beams through a beam splitter were used as probe light. The femtosecond-order time-resolved optical measurement was realized by adjusting a light path length of the probe light (fs pulses). By effectively using this measurement technique, we elucidated the changes of refraction index of the water, the bubble nucleation and growth processes at an interval of femtoseconds, and the bubble properties at an interval of milliseconds. Based on these results, we have elucidated a relationship between those and fs-pulse peak intensity. In addition, we investigated the nucleation and growth processes in femtosecond- to picosecond-order. Finally, we have discovered the water molecules excited by the multi-photon absorption were decomposed into H_2 and O_2 molecules. We found out a new method of hydrogen production.Furthermore, based on the above results, the interactions between a solid transparent material (quartz) and the fs pulses were investigated. An optical fiber was microfabricated by the fs pulses, and a new type optical fiber probe was created. The excellent performances of the probe were demonstrated in micro droplet/bubble measurement (the paper received the Outstanding Paper Award from Institute of Physics, 2010).

飞秒脉冲激光(飞秒脉冲)由于其极高的能量密度而引起非常有趣的现象。对物质的影响不是热效应，而是多光子吸收。当飞秒脉冲的这种多光子吸收在水中工作时，会产生不同于普通激光(如纳米脉冲激光)诱导的空化的特殊现象。在超纯水中，通过几种透镜，获得了脉宽为50-150fs、重复频率为1μ、脉冲能量为0.20-1.4fps的飞秒脉冲。从原始光束通过分束器分离出来的飞秒脉冲被用作探测光。通过调节探测光(飞秒脉冲)的光路长度，实现了飞秒量级的时间分辨光学测量。通过有效地利用这种测量技术，我们解释了水的折射率的变化，气泡在飞秒间隔内的成核和生长过程，以及气泡在毫秒间隔上的性质。基于这些结果，我们阐明了它们与飞秒脉冲峰值强度之间的关系。此外，我们还研究了飞秒到皮秒量级的成核和生长过程。最后，我们发现多光子吸收激发的水分子被分解为H_2和O_2分子。在此基础上，研究了固体透明材料(石英)与飞秒脉冲的相互作用。利用飞秒脉冲微细加工了光纤，制作了一种新型光纤探头。该探头在微滴/气泡测量中表现出优异的性能(该论文获得了2010年中国物理研究所优秀论文奖)。