Interactions between light and material media generally involve an exchange of energy and momentum. Whereas packets of electromagnetic radiation (i.e., photons) are known to carry energy as well as momentum, the eigen-modes of mechanical vibration (i.e., phonons) do not carry any momentum of their own. Considering that, in light-matter interactions, not only the total energy but also the total momentum (i.e., electromagnetic plus mechanical momentum) must be conserved, it becomes necessary to examine the momentum exchange mechanism in some detail. In this presentation, we describe the intricate means by which mechanical momentum is taken up and carried away by material media during reflection, refraction, and absorption of light pulses, thereby ensuring the conservation of linear momentum. Particular attention will be paid to periodically-structured media, which are capable of supporting acoustic as well as optical phonons.
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