  Following our recent idea of using plasmonic and non-plasmonic nanoparticles
as nanoinductors and nanocapacitors in the infrared and optical domains [N.
Engheta, A. Salandrino, and A. Alu, Phys. Rev. Letts., Vol. 95, 095504,
(2005)], in this work we analyze in detail some complex circuit configurations
involving series and parallel combinations of these lumped nanocircuit elements
at optical frequencies. Using numerical simulations, it is demonstrated that,
after a proper design, the behavior of these nanoelements may closely mimic
that of their lower frequency (i.e., radio frequency (RF) and microwave)
counterparts, even in relatively complex configurations. In addition, we
analyze here in detail the concepts of nanoinsulators and nanoconnectors in the
optical domain, demonstrating how these components may be crucial in minimizing
the coupling between adjacent optical nanocircuit elements and in properly
connecting different branches of the nanocircuit. The unit nanomodules for
lumped nanoelements are introduced as building blocks for more complex
nanocircuits at optical frequencies. Numerical simulations of some complex
circuit scenarios considering the frequency response of these nanocircuits are
presented and discussed in details, showing how practical applications of such
optical nanocircuit concepts may indeed be feasible within the current limits
of nanotechnology.
