  An optical characterization tool of Raman spectroscopy with extremely weak
scattering cross section tool is not popular to analyze scattered signal from a
single nanostructure in the sub-diffraction regime. In this regard, plasmonic
assisted characterization tools are only relevant in spectroscopic studies of
nanoscale object in the sub-diffraction limit. We have reported polarized
resonance Raman spectroscopic (RRS) studies with strong electron-phonon
coupling to understand the crystalline orientation of a single AlGaN nanowire
of diameter about 100 nm. AlGaN nanowire is grown by chemical vapor deposition
technique using the catalyst assisted vapor-liquid-solid process. The results
are compared with the high resolution transmission electron microscopic
analysis. As a matter of fact, optical confinement effect due to the dielectric
contrast of nanowire with respect to that of surrounding media assisted with
electron-phonon coupling of RRS are useful for the spectroscopic analysis in
the sub-diffraction limit of 325 nm (lamda(2N.A.)^(-1)) using an excitation
wavelength (lamda) of 325 nm and near ultraviolet 40X far field objective with
a numerical aperture (N.A.) value of 0.50.
