Study on High Frequency Dynamics of Liquid Surface by Laser Induced Surface Vibration Spectroscopy

激光诱导表面振动光谱研究液体表面高频动力学

基本信息

批准号：
11450036
负责人：
SAKAI Keiji
金额：
$ 8.06万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We developed a new technique of picking up the liquid surface in a non-contact manner by a cw-laser radiation. The momentum change of light at the laser transmission through the air-liquid interface appears as the radiation pressure, which deforms the liquid surface into the shape determined by the balance between the Laplace force of the curved surface and the radiation pressure. The displacement of the liquid surface is inversely proportional to the surface tension, which was measured by an optical probe. The dynamic response of the liquid surface deformation was theoretically derived under the periodical modulation of the radiation pressure. The experimentally observed spectra were in good agreement with the theory giving the dynamic properties of the liquid surface.Objectives of microscope were employed to excite the high frequency surface vibration. The laser spot was focused on the liquid surface within the diameter of several microns and the surface vibration was excited over the frequency of 1 MHz.We also tried to excite the wave propagating on the liquid surface with linear a wavefront. The laser light was linearly focused on to the liquid surface with a cylindrical lens with the width of several microns and the length of 200 microns. Coherent wave was successfully excited in the frequency range from 100 Hz up to several tens of kHz. We can accurately determine the mechanical properties on and near the surface, such as surface tension and shear viscosity, by measuring the surface wave propagation.The technique of the laser induced surface deformation (LISD) has a potential as the measurement tool of the surface dynamic properties, such as the time dependent surface tension and surface visco-elasticity.

我们开发了一种通过连续激光辐射以非接触方式拾取液体表面的新技术。激光传输通过气液界面时光的动量变化表现为辐射压力，使液体表面变形为由曲面拉普拉斯力与辐射压力之间的平衡所决定的形状。液体表面的位移与表面张力成反比，表面张力是通过光学探针测量的。理论上推导了辐射压周期性调制下液面变形的动态响应。实验观察到的光谱与给出液体表面动态特性的理论非常吻合。采用显微镜物镜来激发高频表面振动。将激光光斑聚焦在直径几微米的液体表面上，并在1 MHz频率上激发表面振动。我们还尝试用线性波前激发在液体表面传播的波。激光通过宽度为数微米、长度为200微米的柱面透镜线性聚焦到液体表面。在100 Hz到几十kHz的频率范围内成功激发了相干波。通过测量表面波传播，我们可以准确地确定表面及其附近的机械性能，例如表面张力和剪切粘度。激光诱导表面变形（LISD）技术具有作为表面动态测量工具的潜力特性，例如随时间变化的表面张力和表面粘弹性。