Single-molecule spectromicroscopy: a route towards sub-wavelength refractometry

Abstract

We suggest a novel approach for spatially resolved probing of local fluctuations of the refractive index n in solids by means of single-molecule (SM) spectroscopy. It is based on the dependence T₁(n) of the effective radiative lifetime T₁ of dye centres in solids on n due to the local-field effects. Detection of SM zero-phonon lines at low temperatures gives the values of the SM natural spectral linewidth (which is inversely proportional to T₁) and makes it possible to reveal the distribution of the local n values in solids. Here we demonstrate this possibility on the example of amorphous polyethylene and polycrystalline naphthalene doped with terrylene. In particular, we show that the obtained distributions of lifetime limited spectral linewidths of terrylene molecules embedded into these matrices are due to the spatial fluctuations of the refractive index local values.