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Negative Electromagnetic Radiation Pressure

Categories: Laboratory for Surface Modification (LSM)
Speaker: Henri Lezec, NIST, Center for Nanoscale Science and Technology
Date & Time: October 27, 2011 - 12:00pm
Location: CHEM 260

We investigate, both experimentally and theoretically, the radiation pressure exerted by a plane wave of visible-frequency light on a flat slab of dissipative material which is left-handed, i.e. having electric permittivity and magnetic permeability which are both negative [1].
In particular, we characterize the radiation-pressure response of an optical-frequency, broadband, left-handed metamaterial based on stacked Ag/Si/Ag plasmonic waveguides, each designed to be left-handed over most of the visible spectrum. A fully-absorbing flat slab of this metamaterial, integrated onto a low-stiffness cantilever, is shown to experience a pull when illuminated at normal incidence by a plane-wave of free-space wavelength in the range 460 nm to 600 nm. Radiation-induced pull is further confirmed by levitation of free-standing slabs of the metamaterial under illumination at 532nm.
An analytical model is proposed which closely matches, without any adjustable parameters, both magnitude and spectral dependence of the measured pressure response. In this model, the real part of the effective refractive index of the metamaterial contributes to a proportionately-large negative absorption force, which, when it exceeds the always positive Lorentz force, yields in a net negative pressure on the object.
Using finite-difference-time domain simulations, we demonstrate how momentum is conserved under classical Lorentz-force interactions between light wave and slab. In addition, we show how our model for quantum absorption force, based on Doppler-shifted photon exchange between an emitter in the laboratory and an absorber on the cantilever, simultaneously conserves momentum as well. As a result, total system momentum is conserved at all times.

[1] V. Veselago, "The Electrodynamics of Substances with Simultaneously Negative Values of and ," Sov. Phys. Usp., vol. 10, pp. 509-514, 1968.

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