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Applied Optics

Applied Optics


  • Editor: James C. Wyant
  • Vol. 45, Iss. 18 — Jun. 20, 2006
  • pp: 4263–4269

Characterization of objective transmittance for optical tweezers

N. B. Viana, M. S. Rocha, O. N. Mesquita, A. Mazolli, and P. A. Maia Neto  »View Author Affiliations

Applied Optics, Vol. 45, Issue 18, pp. 4263-4269 (2006)

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We have measured the overall transmittance of a laser beam through an oil immersion objective as a function of the transverse size of the laser beam, using the dual-objective method. Our results show that the objective transmittance is not uniform and that its dependence on the radial beam's position can be modeled by a Gaussian function. This property affects the intensity distribution pattern in the sample region and should be taken into account in theoretical descriptions of optical tweezers. Moreover, one must consider this position dependence to determine the local laser power delivered at the sample region by the dual-objective method, especially when the beam overfills the objective's back entrance. If the transmittance is assumed to be uniform, the local power is overestimated.

© 2006 Optical Society of America

OCIS Codes
(110.0180) Imaging systems : Microscopy
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.4640) Instrumentation, measurement, and metrology : Optical instruments
(140.7010) Lasers and laser optics : Laser trapping

ToC Category:
Instrumentation, Measurement, and Metrology

Original Manuscript: August 24, 2005
Revised Manuscript: October 17, 2005
Manuscript Accepted: November 18, 2005

Virtual Issues
Vol. 1, Iss. 7 Virtual Journal for Biomedical Optics

N. B. Viana, M. S. Rocha, O. N. Mesquita, A. Mazolli, and P. A. Maia Neto, "Characterization of objective transmittance for optical tweezers," Appl. Opt. 45, 4263-4269 (2006)

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  11. If the refractive index of sample chamber nS is smaller than the numerical aperture NA, then the rays at a distance p > ≥ Rc = nSRobj/NA from the axis are eliminated by total internal reflection. This is the case for water samples (nS = 1.33) with objectives of 1.4 NA. In this case we could substitute Rc for Robj throughout this section. However, the effect of this replacement is negligible because of the transmittance decay for large radial distances. For instance, Eq. (9) would yield, with Rc instead of Robj, an output power smaller by only 2%.

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