Optical near field in integrated plasmonics on silicon photonics

Abstract

The integration of plasmonic nanostructures on silicon photonics enhances the photonic properties and functionalities of optical devices such as silicon photonic waveguides in the near infrared spectrum. Indeed, the use of electromagnetic surface waves associated with charge density waves on the surface of a conducting material (i.e. surface plasmons-polaritons) could confine and therefore enhance the local electromagnetic field relative to the electromagnetic field in a silicon photonic waveguide. In such a hybrid plasmonic-photonic integrated platform, the surface plasmons-polaritons are used for short-distance and strong interaction with matter while the photonic modes in silicon photonic waveguides are used for long-distance propagation of information. The integration of the plasmonic nanostructures and the photonic waveguides is based on evanescent directional coupling. Due to the subwavelength confinement of the electromagnetic fields in the plasmonic structures, optical near field measurements with the use of near-field scanning optical microscopes (NSOM) are required to reveal and to understand the propagation characteristics of light in integrated plasmonic devices on silicon photonics. The aim of this contribution is to present and to discuss the optical near field images of some integrated plasmonic devices. The interpretation of NSOM images provides a rich understanding of the physical mechanisms involved in plasmonic-photonic integrated structures.