Raman spectroscopy as a probe for the coupling of light into ensembles of sub-wavelength-sized nanowires

We use Raman scattering to investigate how light penetrates into and escapes out of GaN nanowires with diameters and interspacings smaller than the effective wavelength of the light. Quantitatively, the efficiencies for light coupling into and out of the nanowires can be explained by considering the nanowire ensemble as a homogeneous effective medium. The observed phonon modes in the Raman spectra, however, suggest that light enters the nanowires to a considerable extent through their side facets even for normal incidence. This finding is supported by rigorous calculations of the spatially distributed light intensity within a periodic nanowire structure. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747208]