Polarisation-resolved near-field mapping of a coupled gold nanowire array

21.06.2013, 00:00

Newsletter 6

Scanning near-field optical microscopy (SNOM) is a powerful tool for resolving optical features on the nanoscale. We have used SNOM to measure a transverse 2D near-field distribution and have developed a fibre-based calibration technique to measure the local polarisation state of surface plasmon polariton (SPP) modes. The SPPs are guided on a hexagonal array of gold nanowires incorporated into the cladding of a solid-core fused silica photonic crystal fibre (PCF). Because of the close proximity of the nanowires, the individual guided SPPs are coupled to their nearest-neighbours, forming plasmonic supermodes which are excited by launching light into the glass core of the PCF. The guided SPPs show a quadrupolar intensity distribution whose orientation depends on the polarisation of the launched core light. Their local polarisation state is radial, which we were able to resolve using a polarisation-sensitive near-field probe in light-collection mode. All the experimental results were in good agreement with finite-element modelling and coupled-mode-theory. The polarisation-sensitive near-field technique developed is likely to be useful in many areas of nanophotonics.

Contact: patrick.uebel(at)mpl.mpg(dot)de
Group: Russell Division
Reference: P. Uebel et al., Opt. Exp. 20, 28409 (2012); highlighted in Virt. J. of Biomed. Opt. 8 (2013).