  Undoubtedly, Raman spectroscopy is one of the most elaborated spectroscopy
tools in materials science, chemistry, medicine and optics. However, when it
comes to the analysis of nanostructured specimens, accessing the Raman spectra
resulting from an exciting electric field component oriented perpendicularly to
the substrate plane is a difficult task and conventionally can only be achieved
by mechanically tilting the sample, or by sophisticated sample preparation.
Here, we propose a novel experimental method based on the utilization of
polarization tailored light for Raman spectroscopy of individual
nanostructures. As a proof of principle, we create three-dimensional
electromagnetic field distributions at the nanoscale using tightly focused
cylindrical vector beams impinging normally onto the specimen, hence keeping
the conventional beam-path of commercial Raman systems. Using this excitation
scheme, we experimentally show that the recorded Raman spectra of individual
gallium-nitride nanostructures of sub-wavelength diameter used as a test
platform depend sensitively on their location relative to the focal vector
field. The observed Raman spectra can be attributed to the interaction with
transverse or longitudinal electric field components. This novel technique may
pave the way towards a characterization of Raman active nanosystems using full
information of all Raman modes.
