Particle enhanced plasmonic NSOM

Nearfield scanning optical microscopy (NSOM) offers a practical means of optical imaging at a resolution well beyond the diffraction limit of the light. However, its applications are limited due to the strong attenuation of the light transmitted through the sub-wavelength aperture. In this paper, we report the development of particle enhanced plasmonic nearfield scanning optical microscope (PEP-NSOM) with a high optical coupling efficiency and a high spatial resolution. Two plasmonic components, a gold nanoparticle and a plasmonic lens, are integrated on a PEP-NSOM probe. By exciting both propagating surface plasmons and localized surface plasmons, PEP-NSOM probes are capable of focusing light onto the nanoparticle assembled on the aperture of the plasmonic lens, which can further squeeze the light to a few tens of nanometers. Nearfield intensity at the focus points of PEP-NSOM probes is 590 times higher than that of incident light according to numerical simulations. The E-field profile is also shown to be confined laterally <50nm at the imaging plane, which promises good nearfield images with high spatial resolution and low signal-noise ratio. Investigation indicates the local intensity enhancement can be further increased to be 4830 when using a gold nanodimer on the PEP-NSOM probe, which suggests the PEP-NSOM to be an open system of utilizing plasmonic nanostructures for nano-imaging. By providing a strong nano-scale light source, PEP-NSOM can be used as a high speed nano-scale imaging tool for single molecule detection and many other applications requiring high temporal/spatial resolution.