Three-dimensional analysis of the movement of various micron-sized particles under laser radiation pressure

The fundamental characteristics of particle movement in a weakly focused laser beam were investigated from the viewpoint of particle separation. A three-dimensional analysis model based on equations of motion was proposed to clarify the characteristics of the long-range transportation of micron-sized particles having various physical properties. The accuracy of the model was confirmed by measuring the actual movement of a glass, nickel, and aluminum oxide particles. For the glass particle, the calculated trajectory was in good agreement with the measured one. For the nickel particle, the calculation gave a qualitatively correct result. From the measured movements of irregular shaped aluminum oxide particles, it was clarified that the shape of the particle affected its transport distance as well as its refractive index. The possibilities of particle separation based on a difference in refractive index and shape were suggested because the transport distance of a particle depended on these factors.