Optical manipulation is a term we use to encompass the application of optical forces to move, guide and trap (in 2D and 3D) mesoscopic objects.  Optical tweezers – single beam 3D trapping - is the method we describe here in most detail given its importance for the field of Biophotonics. Optical tweezers relies upon a highly inhomogeneous spatial field distribution of the beam.  This causes a small but significant optical force (~pN) to act upon a dielectric or biological particle (of higher refractive index than its surroundings) near the focus and is the case we deal with here.  This attracts the particle towards the highest intensity part of the field through what is commonly termed the gradient (dipole) force.

Our group has been very active in the last decade at various advances within this field. In particular we have pioneered new methods of passive optical sorting both in the near and far field, explored the use of vortex and 'non-diffracting' light fields, looked at the concept of optical binding and recently developed the first ever trapping through turbulent media.

Reviews

Light forces the pace: Optical manipulation for Biophotonics, D.J. Stevenson, F. Gunn-Moore and K. Dholakia, J. Biomed. Opt 15(2), 041503 (2010) (highlighted in SPIE Reviews and the Virtual Journal of Biological Physics Research)

Light beats the spread: “non-diffracting” beams, Michael Mazilu, David J. Stevenson, Frank J. Gunn-Moore and Kishan Dholakia, Laser & Photonics Reviews 4 (4), 529 - 547 (2010).

Gripped by light: Optical Binding Kishan Dholakia and Pavel Zemánek, Reviews of Modern Physics 82, 1767–1791 (2010)

Optical trapping takes shape: the use of structured light fields, K Dholakia and WM Lee, Advances In Atomic, Molecular, and Optical Physics 56, 261-337 (2008) (pdf)

Some of our Key Papers (please see publications for full list)

In situ wave-front correction: application to micromanipulation T Čižmár, M Mazilu and K Dholakia, Nature Photonics 4, 388 - 394 (2010) (highlighted in Nature Photonics News & Views)

Optically mediated particle clearing using Airy wavepackets, Jörg Baumgartl, Michael Mazilu & Kishan Dholakia. Nature Photonics 2, 675-678 (2008)

Long-range one-dimensional longitudinal optical binding, V. Karásek, T. Čižmár, O. Brzobohatý, P. Zemánek, V. Garcés-Chávez, and K. Dholakia, Phys. Rev. Lett. 101, 143601 (2008)

Microfluidic Sorting in an Optical Lattice (link to article) 
M.P. MacDonald, G.C. Splading and K. Dholakia, Nature 426, 421 (2003)

Simultaneous micromanipulation in multiple planes using a self-reconstructing light beam (pdf) (link to article - restricted) V. Garcés-Chávez, D. McGloin, H. Melville, W. Sibbett and K. Dholakia, Nature 419, 145 (2002).

Creation and Manipulation of Three-Dimensional Optically Trapped Structures
M. P. MacDonald, L. Paterson, K. Volke-Sepulveda, J. Arlt, W. Sibbett, and K. Dholakia, Science 296, 1101-1103 (2002)

Controlled Rotation of Optically Trapped Microscopic Particles
L. Paterson, M. P. MacDonald, J. Arlt, W. Sibbett, P. E. Bryant and K. Dholakia, Science 292, 912-914 (2001)

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