Development of All Optical, Super Precise manipulator

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Optical trapping technique, which uses a strongly focused laser beam, has been an important tool for the precise manipulation of micrometer-sized particles such as polystirene latex spheres and biological cells. For these particles, a force generated by refraction at the particle surface is thought to contribute significantly to optical trapping because a large fraction of light is refracted. Therefore, a strongly absorptive particle, which has a large complex index of refraction, has been considered to be difficult to trap optically. We succeeded in trapping three kinds of micrometer-sized metal particles with a fixed, nonscanning laser beam. On the basis of the ray optics, kinetic forces generated by the momentum transmission from the light, is calculated for metal particles. As a result, the facts observed experimentally are well explained with the calculated results. Possibility to trap other materials such as semiconductors is also predicted by the force calculations. This means the optical trapping technique is able to be widely applied in various fields of basic and applied studies.Furthermore, we performed a basic experiments of an optical hererodyne interferometry, which has spatial resolution of nanometer. It is thought that a basic technology for all optical, precise manipulator is established by combining the optical trapping and the heterodyne interferometry techniques.