Abstract

Metallic particles are generally considered difficult to trap due to strong scattering and absorption forces. In this paper, numerical studies show that optical tweezers using radial polarization can stably trap metallic particles in 3-dimension. The extremely strong axial component of a highly focused radially polarized beam provides a large gradient force. Meanwhile, this strong axial field component does not contribute to the Poynting vector along the optical axis. Consequently, it does not create axial scattering/absorption forces. Owing to the spatial separation of the gradient force and scattering/absorption forces, a stable 3-D optical trap for metallic particles can be formed.

© 2004 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. A. Ashkin, �??Acceleration and trapping of particles by radiation pressure,�?? Phys. Rev. Lett. 24, 156-159, (1970).
    [CrossRef]
  2. A. Ashkin, �??History of optical trapping and manipulation of small-neutral particle, atoms, and molecules,�?? IEEE J. Sel. Top. Quantum Electron 6, 841-856, (2000).
    [CrossRef]
  3. K. Svoboda and S. M. Block, �??Optical trapping of metallic Rayleigh particles,�?? Opt. Lett. 19, 930-932, (1994).
    [CrossRef] [PubMed]
  4. M. Gu and D. Morrish, �??Three-dimensional trapping of Mie metallic particles by the use of obstructed laser beams,�?? J. Appl. Phys., 91, 1606-1612, (2002).
    [CrossRef]
  5. S. Sato, Y. Harada and Y. Waseda, �??Optical trapping of microscopic metal particles,�?? Opt. Lett. 19, 1807-1809 (1994)
    [CrossRef] [PubMed]
  6. Q. Zhan and J. R. Leger, "Focus shaping using cylindrical vector beams," Opt. Express 10, 324-331 (2002), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-10-7-324">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-10-7-324</a>
    [CrossRef] [PubMed]
  7. Q. Zhan, �??Optical radiation forces on a dielectric sphere produced by highly focused cylindrical vector beams,�?? J. Opt. A: pure appl. opt., 5, 229-232, (2003).
    [CrossRef]
  8. R. Dorn, S Qubis, and G. Leuchs, �??Sharper focus for a radially polarized light beam,�?? Phys. Rev. Lett. 91, 233901, (2003).
    [CrossRef] [PubMed]
  9. S. Quabis, R. Dorn, M. Eberler, O. Glöckl and G. Leuchs, �??Focusing light into a tighter spot,�?? Opt. Commun. 179, 1-7 (2000).
    [CrossRef]
  10. K. S. Youngworth and T. G. Brown, �??Focusing of high numerical aperture cylindrical vector beams,�?? Opt. Express 7, 77-87 (2000), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-2-77.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-7-2-77."</a>
    [CrossRef] [PubMed]
  11. H. Kano, S. Mizuguchi and S. Kawata, �??Excitation of surface-plasmon polaritons by a focused laser beam,�?? J. Opt. Soc. Am. B. 15, 1381-1386 (1998).
    [CrossRef]
  12. E. Wolf, �??Electromagnetic diffraction in optical systems I. An integral representation of the image field,�?? Proc. R. Soc. Ser. A 253, 349-357 (1959).
    [CrossRef]
  13. B. Richards and E. Wolf, �??Electromagnetic diffraction in optical systems II. Structure of the image field in an aplanatic system,�?? Proc. R. Soc. London Ser. A 253, 358-379 (1959).
    [CrossRef]
  14. M. Kerker, The Scattering of Light and Other Electromagnetic Radiation, Academic (New York), 1969.
  15. Y. Harada, T. Asakura, �??Radiation forces on a dielectric sphere in the Rayleigh scattering regime,�?? Opt. Commun. 124, 529-541 (1996).
    [CrossRef]
  16. A. Ashkin, J. M. Dziedzic, J. E. Bjorkholm, and S. Chu, �??Observation of a single-beam gradient force optical trap for dielectric particles,�?? Opt. Lett. 11, 288-290, (1986).
    [CrossRef] [PubMed]

IEEE J. Sel. Top. Quantum Electron

A. Ashkin, �??History of optical trapping and manipulation of small-neutral particle, atoms, and molecules,�?? IEEE J. Sel. Top. Quantum Electron 6, 841-856, (2000).
[CrossRef]

J. Appl. Phys.

M. Gu and D. Morrish, �??Three-dimensional trapping of Mie metallic particles by the use of obstructed laser beams,�?? J. Appl. Phys., 91, 1606-1612, (2002).
[CrossRef]

J. Opt. A: pure appl. opt.

Q. Zhan, �??Optical radiation forces on a dielectric sphere produced by highly focused cylindrical vector beams,�?? J. Opt. A: pure appl. opt., 5, 229-232, (2003).
[CrossRef]

J. Opt. Soc. Am. B.

H. Kano, S. Mizuguchi and S. Kawata, �??Excitation of surface-plasmon polaritons by a focused laser beam,�?? J. Opt. Soc. Am. B. 15, 1381-1386 (1998).
[CrossRef]

Opt. Commun.

S. Quabis, R. Dorn, M. Eberler, O. Glöckl and G. Leuchs, �??Focusing light into a tighter spot,�?? Opt. Commun. 179, 1-7 (2000).
[CrossRef]

Y. Harada, T. Asakura, �??Radiation forces on a dielectric sphere in the Rayleigh scattering regime,�?? Opt. Commun. 124, 529-541 (1996).
[CrossRef]

Opt. Express

Opt. Lett.

Phys. Rev. Lett.

A. Ashkin, �??Acceleration and trapping of particles by radiation pressure,�?? Phys. Rev. Lett. 24, 156-159, (1970).
[CrossRef]

R. Dorn, S Qubis, and G. Leuchs, �??Sharper focus for a radially polarized light beam,�?? Phys. Rev. Lett. 91, 233901, (2003).
[CrossRef] [PubMed]

Proc. R. Soc. London Ser. A

B. Richards and E. Wolf, �??Electromagnetic diffraction in optical systems II. Structure of the image field in an aplanatic system,�?? Proc. R. Soc. London Ser. A 253, 358-379 (1959).
[CrossRef]

Proc. R. Soc. Ser. A

E. Wolf, �??Electromagnetic diffraction in optical systems I. An integral representation of the image field,�?? Proc. R. Soc. Ser. A 253, 349-357 (1959).
[CrossRef]

Other

M. Kerker, The Scattering of Light and Other Electromagnetic Radiation, Academic (New York), 1969.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1.
Fig. 1.

Geometry used in the optical trapping calculation. Q(r, φ) is an observation point in the focal plane. The particle to be trapped is at the focus.

Fig. 2.
Fig. 2.

Line scan of calculated focal plane energy density distribution for a highly focused radial polarization. It can be seen that axial component is dominant. For comparison, result for linearly polarized incident is also shown (green line).

Fig. 3.
Fig. 3.

Calculated axial component of time averaged Poynting vector for a highly focused radial polarization. (a) 2-dimensional distribution near focus; (b) line scan of (a) at the focal plane.

Fig. 4.
Fig. 4.

Calculated radiation forces on 38.2 nm (diameter) gold particle. (a) Transverse gradient force along x-axis; (b) axial gradient force along z-axis; (c) sum of axial scattering and absorption forces along z-axis; (d) sum of axial scattering and absorption forces on x-axis. For comparison, result for highly focused linearly polarized incident is also shown (red dotted lines)

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

E ( r , φ , z ) = E r e r + E z e z
E r ( r , φ , z ) = 2 A 0 θ mx cos 1 2 ( θ ) P ( θ ) sin θ cos θ J 1 ( k r sin θ ) e i k 1 z cos θ d θ
E z ( r , φ , z ) = i 2 A 0 θ mx cos 1 2 ( θ ) P ( θ ) sin 2 θ J 0 ( k r sin θ ) e i k 1 z cos θ d θ
P ( θ ) = { P 0 if sin 1 ( N A 1 ) θ sin 1 ( N A n 1 ) 0 otherwise

Metrics