Optical 'gecko toe': Near-field force sticks a metamaterial to any surface

Zhang, J., MacDonald, K.F. and Zheludev, N.I. (2012) Optical 'gecko toe': Near-field force sticks a metamaterial to any surface. SPIE Photonics Europe 2012, , Brussels, Belgium. 16 - 19 Apr 2012.

Abstract

We have identified a new type of optically-driven force, the near-field force of attraction between an illuminated planar plasmonic metamaterial and a dielectric or metallic surface. This force provides an optically controlled adhesion mechanism mimicking the gecko toe van der Waals attraction. It can be orders of magnitude stronger than conventional radiation pressure, can exceed the Casimir forces in the system and at illumination intensities of just a few tens of nW/µm² it can overcome the Earth's gravitational pull on a metamaterial located within a few tens of nanometres of a surface.
This newly identified near-field force has a resonant nature linked to the confinement of energy in the metamaterial's plasmonic mode and acts to close the gap between the metamaterial film and the surface. It has been evaluated for different types of metamaterial using both the Maxwell stress tensor formulism and the energy gradient approach, which coincide in predicting the magnitude and the resonant frequency dependence of the force on the wavelength of external excitation.
The near-field force holds considerable advantages for nanoscale manipulation in that it depends on both light intensity and wavelength - offering dynamic controllability and spectral selectivity. It may serve applications in optical trapping/tweezing and in the control of light with light via optically reconfigurable metamaterials.

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Contributors

Author: K.F. MacDonald

Author: N.I. Zheludev

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