We have already developed an optical fiber trapping system and verified that optical trapping and manipulation of a micro object were easily achieved by a focused laser beam emerging from an optical fiber inserted into a sample chamber. In this paper, we described the performance of an optical fiber trap realized using a tapered hemispherically lensed optical fiber and experimentally analyzed the axial and transverse optical forces exerted on a micro-sphere to corroborate the optical trapping using a lensed optical fiber.
Experimental results were as follows. (i) Transverse force
Ftr, acting on a sphere was restoring force that acted to pull the micro-sphere back to the center of trap. (ii) Axial force
Fax always acted 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 gave a restoring force directed back to the stable point. (iv) Transverse force played a significant role in trapping a micro-sized object by means of an optical fiber.
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