  Nanostructures have become an attractive subject due to many applications,
particularly the photonic bandgap effect observed in photonic crystals.
Nevertheless, the fabrication of such structures remains a challenge because of
accurate requirement concerning regularity, shape, hole depth etc. of the
structure. E-beam lithography permits a good control of dimensional parameters
but needs a 1-step fabrication process. In our work, we have to combine
traditional strip-load waveguides (SiO2/SiON/SiO2 on Si) and nanostructures
whose dimension are totally different. This imposes a 2-step process where
waveguides and nanostructures are successively fabricated. We have at our
disposal different ways to characterize these nanostructures. A direct aspect
control during and after FIB treatment can be achieved by FIB and SEM imaging.
Scanning near-field optical microscopy (SNOM) is currently the most effective
way to test guiding confinement in such surface structures by detecting the
evanescent field.
