[OPTICAL REVIEW Vol. 6, No. 3 (1999) 224-226]

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

Kozo TAGUCHI, Kentaro ATSUTA, Takeshi NAKATA and Masahiro IKEDA

Department of Electronics and Electrical Engineering, Fukuyama University, Gakuen-cho, Fukuyama, Hiroshima, 729-0292 Japan

(Received December 7, 1998; Accepted December 28, 1998)

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.

Key words : optical fiber, laser beam effects, optical trapping, axial trapping force, transverse trapping force