Mapping of surface plasmon polaritons on nanostructured thin film disks using cathodoluminescence imaging

Abstract

In this paper we report investigations on mapping of surface plasmon polaritons (SPPs) on nanostructured thin film disks using electron-beam excitation. Square and circular disks with sub-micron characteristic dimensions were patterned using electron-beam lithography. Two-dimensional confinement of SPPs resulted into standing wave patterns that were imaged using cathodoluminescence spectroscopy. Several modes of the disks were identified and were found to be dependent on disk geometry as well as position of the electron beam. Detailed analysis of specific modes is provided using panchromatic imaging of the disks. SPP wavelengths as small as 100 nm are predicted from the dispersion curves of 15 nm thick Ag films. Extremely small mode volumes on disks as small as 65 nm are mapped. Our investigations enhance understanding of light-matter interaction at nanoscale with potential applications in various areas including photonics, optoelectronics, chemical and biological sensing, and next generation optical communication. © 2011 SPIE.