  We exploit the near field enhancement of nano-antennas to investigate the
Raman spectra of otherwise not optically detectable carbon nanotubes (CNTs). We
demonstrate that a top-down fabrication approach is particularly promising when
applied to CNTs, owing to the sharp dependence of the scattered intensity on
the angle between incident light polarization and CNT axis. In contrast to tip
enhancement techniques, our method enables us to control the light polarization
in the sample plane, locally amplifying and rotating the incident field and
hence optimizing the Raman signal. Such promising features are confirmed by
numerical simulations presented here. The relative ease of fabrication and
alignment makes this technique suitable for the realization of integrated
devices that combine scanning probe, optical, and transport characterization.
