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Proceedings Paper

Manipulation of optically levitated particles
Author(s): Oscar Isaksson; Magnus Karlsteen; Mats Rostedt; Dag Hanstorp
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Paper Abstract

The development of an experimental system in which optical levitation combined with Millikan´s classical oil drop experiment will be presented. The focus of the apparatus is a glass cell (25x72x25 mm3) in which an oil drop is levitated using a vertically aligned laser beam. A laser power of about 0.9 W is needed to capture a drop, whereas typically 0.3 W is sufficient to maintain it in the trap. An alternating electric field is applied vertically across the cell, causing the drop to oscillate in the vertical direction. The amplitude of the oscillations depends on the strength of the electric field and the q/m ratio of the oil drop. The oscillations are observed by imaging scattered laser light onto either a screen or a position sensitive detector. The number of discrete charges on the drop can be reduced by exposing it to either UV-light or a radioactive source. The radius of the drop is measured by detecting the diffraction pattern produced when illuminated with a horizontally aligned He-Ne laser beam. The mass of the drop can then be determined since the density of the oil is known. Hence, absolute measurements of both the mass and the charge of the drop can be obtained. The goal of the experiment is to design a system which can be used to demonstrate several fundamental physical phenomena using the bare eye as the only detector. The experimental set-up will be further developed for studies of light scattering and spectroscopy of liquids and for studies of interactions between liquid drops.

Paper Details

Date Published: 12 September 2013
PDF: 8 pages
Proc. SPIE 8810, Optical Trapping and Optical Micromanipulation X, 88100O (12 September 2013); doi: 10.1117/12.2023860
Show Author Affiliations
Oscar Isaksson, Chalmers Univ. of Technology (Sweden)
Univ. of Gothenburg (Sweden)
Magnus Karlsteen, Chalmers Univ. of Technology (Sweden)
Mats Rostedt, Univ. of Gothenburg (Sweden)
Dag Hanstorp, Univ. of Gothenburg (Sweden)

Published in SPIE Proceedings Vol. 8810:
Optical Trapping and Optical Micromanipulation X
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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