Electromagnetic energy storage and power dissipation in nanostructures

• Presented a combined analysis of local energy storage and power dissipation in nanostructures.
• Related the absorption enhancement and energy storage enhancement.
• Obtained a lower limit for the electric energy density of general lossy dispersive media.
• Strong local field enhancement at resonance is interpreted from the energy storage point of view.

The processes of storage and dissipation of electromagnetic energy in nanostructures depend on both the material properties and the geometry. In this paper, the distributions of local energy density and power dissipation in nanogratings are investigated using the rigorous coupled-wave analysis. It is demonstrated that the enhancement of absorption is accompanied by the enhancement of energy storage both for material at the resonance of its dielectric function described by the classical Lorentz oscillator and for nanostructures at the resonance induced by its geometric arrangement. The appearance of strong local electric field in nanogratings at the geometry-induced resonance is directly related to the maximum electric energy storage. Analysis of the local energy storage and dissipation can also help gain a better understanding of the global energy storage and dissipation in nanostructures for photovoltaic and heat transfer applications.