Fluorophore interactions with nano-layered metamaterials

Recently, devices called `superlenses` have been receiving a lot of attention, particularly in the context of near-field imaging technology and cloaking devices. Such superlenses can consist of stacked sub-wavelength thick metal- dielectric layers that can be coated onto a substrate. The proposed project constitutes an investigation into the optical electromagnetic response properties of several metal/dielectric stacks forming such a "superlens". The parameters of these stacks can be tuned to support various resonant and non-resonant excitations, many of which have yet to be experimentally studied in detail. An investigation of their interactions with fluorescent emitters can be used to study these excitations and is of prime interest for various fields such as nano-optics and fluorescence imaging. We will investigate the superlens transmission and reflection properties, as well as the fluorescence modifications of (single) fluorescent emitters (lifetime, spectral shift) when they are placed at well defined distances in the close vicinity of the superlens surface. If the superlenses indeed support the excitation/dissipation and transmission modes predicted, these would directly be manifested in a change in lifetime, observed quenching in far-field measurements, enhanced or reduced transmission through the superlens and, when relevant, the image-plane intensity profile. Exactly how each of these vary as a function of emitter-superlens distance and emitter frequency will allow us to confirm or negate any predicted (waveguiding, plasmonic, excitonic) modes supported by the metal-dielectric stacked superlenses.

This interdisciplinary project shows how to pinpoint and tweak mutual interactions of common fluorescent molecules on specially designed biocompatible surfaces. For thin metal-dielectric coated quartz slides we demonstrated that such coating allow for an optical read-out of the exact distance between coating and the fluorescent molecule with a precision of 5-10 nm. This provides us with a fascinating microscopy tool for (biological) fluorescence imaging that operates far beyond the common 250 nm resolution limit of light microscopy. A resolution power beyond the usual optical limit is often referred to as superresolution. "Functional" super-resolution microscopy as in our case uses clever experimental techniques and tricks borrowed from physics and material sciences to reconstruct a super-resolved image. What are the motivation and prerequisites to realize our approach? First, optical nano-sectioning within a submicron region above an interface is highly desirable for many disciplines in the life sciences, particularly when it comes to investigations of membrane proteins. However, such nano-sectioning is often the Achilles heel of most light microscopy techniques with difficulties to obtain high resolution in depth. Second, a drawback to most current approaches is the a priori need to physically scan in the axial dimension, which can be undesirable for optically sensitive or highly dynamic biological