Experimental Analysis of Optical Trapping System Using Tapered Hemispherically Lensed Optical Fiber

Abstract

We describe the operation and performance of an optical fiber trap realized using a tapered hemispherically lensed optical fiber. Axial and transverse trapping forces exerted on a microsphere are experimentally analyzed to corroborate the optical trapping using an optical fiber. Experimental results are as follows. (i) Transverse force Ftr acting on a sphere is a restoring force that acts to pull the microsphere back to the center of trap. (ii) Axial force Fax always acts to push a sphere in the direction of the beam away from the trapping fiber end. (iii) Vector sum of Ftr and Fax acting on a sphere gives a restoring force directed back to the stable point. (iv) Transverse force Ftr plays a significant role in trapping a micro-sized object by means of an optical fiber.