  Interactions between light and conducting nanostructures can result in a
variety of novel and fascinating phenomena. These properties may have wide
applications, but their underlying mechanisms have not been completely
understood. From calculations of surface charge density waves on conducting
gratings and by comparing them with classical surface plasmons, we revealed a
general yet concrete picture about coupling of light to free electron
oscillation on structured conducting surfaces that can lead to oscillating
subwavelength charge patterns (i.e., spoof surface plasmons but without the
dispersion property of classical surface plasmons). New wavelets emitted from
these light sources then destructively interfere to form evanescent waves. This
principle, usually combined with other mechanisms (e.g. resonance), is mainly a
geometrical effect that can be universally involved in light scattering from
all periodic and nonperiodic structures containing free electrons, including
perfect conductors. The spoof surface plasmon picture may provide clear
guidelines for developing metamaterial-based nano-optical devices.
