Revisiting the Balazs thought experiment in the presence of loss: electromagnetic-pulse-induced displacement of a positive-index slab having arbitrary complex permittivity and permeability |
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Authors: | Kenneth J Chau Henri J Lezec |
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Institution: | 1.Center for Nanoscale Science and Technology,National Institute of Standards and Technology,Gaithersburg,USA;2.School of Engineering,The University of British Columbia,Kelowna,Canada |
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Abstract: | Over a half-century ago, Balazs proposed a thought experiment to deduce the form of electromagnetic momentum in a lossless
and non-dispersive slab by imposing conservation of global momentum and system center-of-mass velocity after a pulse has traveled
through the slab. Here, we revisit the Balazs thought experiment by explicit calculations of momentum transfer and center-of-mass
displacement of a non-dispersive, positive-index slab of arbitrary complex permittivity and permeability using a set of postulates
consisting only of Maxwell’s equations, a generalized Lorentz force law, the Abraham form of the electromagnetic momentum
density, and conservation of both pulse and slab mass. In the case where the slab is lossless, we show that a pulse of arbitrary
shape incident onto the slab conserves both global momentum and system center-of-mass velocity, consistent with the starting
postulates of the Balazs thought experiment. In the case where the slab is lossy, we show, within the context of the above
postulates, that global momentum is always conserved and that system center-of-mass velocity is conserved only when mass transfer
from the pulse to the slab is described by an incremental pulse-mass-transfer model, proposed here, in which the pulse deposits
mass in the slab with a distribution corresponding to the instantaneous mass density profile of the pulse. |
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