Study on Micro-machining Using a Small Particle Controlled by Optical Pressure.

基于激光俘获技术，提出了一种利用聚焦激光产生的光辐射压力控制小颗粒微加工的新方法。已知在光辐射压力作用下，几微米大小的粒子可以被捕获并在液体中移动，这种压力小到pN到nN。这就是所谓的激光捕获技术。我们提出了一种新的微加工方法，利用光辐射压力控制小介电颗粒，如金刚石颗粒或硅球作为加工工具。为了验证我们提出的微加工的可行性，首先，我们进行了捕获力的计算机模拟。仿真结果表明，较大数值孔径的物镜和较大折射率的颗粒适合于这种微加工。其次，构建实验系统，并根据仿真结果进行基础实验。激光捕获的直径颗粒在加工液中沿恒定路径在硅片表面运动数百次。然后，用原子力显微镜观察待加工表面。从AFM图像中发现，即使压力小到0.1nN，金刚石颗粒也会去除几纳米深度的硅片表面。此外，旋转金刚石颗粒的微加工效率高于非旋转金刚石颗粒，并且即使折射率较小的硅球也可以对机械强度较低的表面进行微加工。

This paper presents a new micromachining using a small particle controlled by optical radiation pressure induced by focused laser light, which is based on laser trapping technology. It is known that the particle of several micrometer can be trapped and moved in liquid by optical radiation pressure force, which is as small as pN to nN. it is so called laser trapping technology. We propose the new micromachining using a small dielectric particle, like a diamond grain or a silica sphere, controlled by optical radiation pressure as a machining tool. In order to verify the feasibility of our proposed micromachining, at first, we perform computer simulation of trapping force. The simulation results suggest that the objective with larger numerical aperture and the particles with larger refractive index are suitable for this micromachining. Second, we construct the experimental system and carry out the fundamental experiments based on the simulation results. The laser trapped diameter grain is moved at the constant path in hundreds of times on the silicon wafer surface in machining liquid. After that, the surface to be machined is observed by using AFM. From the AFM image, it is found that the diamond grain removes the silicon wafer surface with the depth of several nanometer, even if the pressure force is as a small as 0.1nN. Furthermore, it is suggested that rotating diamond grain is more efficient for micromachining than non-rotating diamond grain, and that even a silica sphere with smaller refractive index will be able to perform micromachinng for the surface with low mechanical strength.