Micromanipulation of cells and microparticles using optical fibers

Abstract

Optical tweezers is a powerful tool which is used to capture and manipulate microscopic particles such as dielectric microspheres and cells. In the single optical trap the beam is strongly focused to a diffraction limited spot by a high numerical aperture objective. Resently a new version of optical trap was demonstrated with optical fibers. Compared with the common optical tweezers which required high power microscope objective and carefully adjusted optical path, the fiber optical tweezers are compact in size and less expensive. Moreover, they have also a working distance not necessarily close to the objective as for a typical optical tweezers.In this work we present the development of a single beam optical fiber trapping system integrated with an optical fiber ablation system for micromanipulation of biological objects. The fiber trap was formed using a continuous wave He-Ne laser operating at 632.8 nm. The fiber ablation system was formed using a free-running Er:YAG laser operating at 2.94 m with pulse duration of 80 m. The ablation beam was coupled into the front end of a fluoride glass optical fiber via a focusing lens of 100 mm and a pinhole of 50 m. We evaluated the fluoride glass optical fiber as far as attenuation and as far as the spatial distribution of the energy output is concerned. We verified that optical trapping and the micromanipulation of micro objects were easily achieved, by a focused laser beam, emerging from optical fiber inclined at 42 degrees to the sample.