We report on confocal scanning imaging through highly scattering media. Various practical effects including those of the annular pupils and the size of the confocal pinhole as well as of the numerical aperture of objectives on the image quality are examined xperimentally. The combination of an annular objective with a finitesized detector may prove advantageous for improving image quality.
Plasmonic nano-antennas have proven the outstanding ability of sensing chemical and physical processes down to the nanometer scale. Sensing is usually achieved within the highly confined optical fields generated resonantly by the nano-antennas, i.e. in contact to the nanostructures. In this paper, we demonstrate the sensing capability of nano-antennas to their larger scale environment, well beyond their plasmonic confinement volume, leading to the concept of "remote" (non contact) sensing on the nanometer scale. On the basis of a bowtie-aperture nano-antenna (BNA) integrated at the apex of a SNOM fiber tip, we introduce an ultra-compact, moveable and background-free optical nanosensor for the remote sensing of a silicon surface (up to distance of 300 nm). Sensitivity of the BNA to its large scale environment is high enough to expect the monitoring and control of the spacing between the nano-antenna and a silicon surface with sub-nanometer accuracy. This work paves the way towards a new class of nanopositionning technique, based on nano-antenna resonance monitoring, that are alternative to nanomechanical and optical interference-based devices.
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