Far field photoluminescence imaging of single AlGaN nanowire in the sub-diffraction length scale using optical confinement of polarized light

TL;DR

This paper demonstrates far-field photoluminescence imaging of a single AlGaN nanowire at sub-diffraction scales by exploiting optical confinement of polarized light, revealing proximity-induced PL enhancement due to stimulated emission.

Contribution

It introduces a novel far-field imaging method for single nanowires using polarized light confinement, achieving sub-diffraction resolution without plasmonic structures.

Findings

PL intensity scales as 1/(l×d) with NW length and separation

Proximity induces stimulated emission enhancing PL

Achieved imaging of single nanowire beyond diffraction limit

Abstract

Till now the nanoscale focussing and imaging in the sub-diffraction limit is achieved mainly with the help of plasmonic field enhancement assisted with noble metal nanoparticles. Using far field imaging technique, we have recorded polarized spectroscopic photoluminescence (PL) imaging of a single AlGaN nanowire (NW) of diameter ~ 100 nm using confinement of polarized light. The nanowires on the substrate have a nematic ordering. It is found that the PL from a single NW is influenced by the proximity to other NWs with the PL intensity scaling as 1/(lxd), where l and d are the NW length and the separation from the neighbouring NW, respectively. We show that this proximity induced PL intensity enhancement can be understood, if we assume the existence of reasonably long lived photons in the intervening space between the NWs. A nonzero non-equilibrium population of such photons causes stimulated emission leading to the enhanced PL emission with the intensity scaling as 1/(lxd). The effect is analogous to the Purcell enhancement of polarized optical emissions induced by confined photons in micro-cavities. The enhancement of PL emission facilitated the far field spectroscopic imaging of a single semiconducting nanowire in the sub-diffraction regime.