New technique of single-beam gradient-force laser trapping in air condition

Laser trapping is becoming an important technique for microsystem technologies. To apply it to industrial uses, it should be developed to function in air. However, there is not much research about laser trapping in air. One of the reasons is the difficulty of trapping micro-objects. Therefore, we have proposed a new technique to trap micro-objects in air. In particular, we focused our attention on the substrate where the micro-object is set. By applying a textured surface and employing tungsten carbide as the substrate material, the trapping probability was improved by a remarkable amount. Although a certain degree of improvement was attained, the trapping was still not perfect. To ascertain the forces working on the micro-object, an analytical calculation of the adhesion forces and an electromagnetic simulation of the optical forces were implemented. Based on these calculations, we discuss what the most important factor is for successful laser trapping in air.