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We numerically model the axial trapping forces within optical tweezers arising from Laguerre-Gaussian laser modes. For an 8 mu m diameter sphere suspended in water, the higher-order modes produce an axial trapping force several times larger than that of the fundamental. Partial absorption results in a transfer of the orbital angular momentum from the Laguerre-Gaussian mode to the trapped particle. This results in the rotation of the particle by what may be called an optical spanner (wrench). For an absorption coefficient of alpha = 5700 m(-1) and a laser power of 10 mW, we find that an 8 mu m diameter sphere would acquire an angular acceleration of 10 x 10(4) rad s(-2) and a limiting angular velocity of 0.2 rad s(-1).
|Keywords:||Wollaston prism; multichannel Fourier-transform spectroscopy; field of view; optical throughput; etendue|
|Glasgow Author(s) Enlighten ID:||Padgett, Prof Miles|
|Authors:||Simpson, N., Allen, L., and Padgett, M.|
|College/School:||College of Science and Engineering > School of Physics and Astronomy|
|Journal Name:||Journal of Modern Optics|
|Journal Abbr.:||J. Mod. Opt.|