On resolving the refractive index and the wave vector
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Updated: Jul 19, 2026

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
Published on: August 13, 2019
1Department of Electronics and Telecommunications, Norwegian University of Science and Technology, Trondheim, Norway. johannes.skaar@iet.ntnu.no
Abstract:
The identification of the refractive index and the wave vector for general (possibly active) linear, isotropic, homogeneous, and nonspatially dispersive media is discussed. Correct conditions for negative refraction necessarily include the global properties of the permittivity and permeability functions epsilon=epsilon(omega) and mu=mu(omega). On the other hand, a necessary and sufficient condition for left handedness can be identified at a single frequency (Re epsilon/|epsilon|+Re mu/|mu|<0). At oblique incidence to semi-infinite, active media, it is explained that the wave vector generally loses its usual interpretation for real frequencies.
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