page_title: Sarfus
section_title: Principles
hierarchical_section_title: Sarfus / Principles
caption_attribution_description: English: Polarisation state of light reflected on a Surf (0) and on a sample on the Surf (1). Français&#160;: Etat de la polarisation de la lumière réfléchie par le Surf (0) et par un échantillon présent sur le Surf (1)
context_page_description: Sarfus is an optical quantitative imaging technique based on the association of:
  an upright or inverted optical microscope in crossed polarization configuration and
  specific supporting plates – called surfs – on which the sample to observe is deposited.
  Sarfus visualization is based on the perfect control of the reflection properties of polarized light on a surface, which leads to an increase in the axial sensitivity of optical microscope by a factor of around 100 without reducing its lateral resolution. Thus this new technique increases the sensitivity of standard optical microscope to a point that it becomes possible to directly visualize thin films and isolated nano-objects in real-time, be it in air or in water.
context_section_description: A recent study on polarized light coherence leads to the development of new supports – the surfs – having contrast amplification properties for standard optical microscopy in cross polarizers mode. Made of optical layers on an opaque or transparent substrate, these supports do not modify the light polarization after reflection even if the numerical aperture of the incident source is important. This property is modified when a sample is present on a surf, a non-null light component is then detected after the analyzer rendering the sample visible.
  The performances of these supports are estimated from the measurement of the contrast (C) of the sample defines by: C = (I₁-I₀)/(I₀+I₁) where I₀ and I₁ represent the intensities reflected by the bare surf and by the analyzed sample on the surf, respectively. For a one nanometer-film thickness, the surfs display a contrast 200 times higher than on silicon wafer.
  This high contrast increase allows the visualization with standard optical microscope of films with thicknesses down to 0.3 nm, as well as nano-objects (down to 2 nm diameter) and this, without any kind of sample labelling (neither fluorescence, nor radioactive marker). An illustration of the contrast enhance is given hereafter with the observation in optical microscopy between cross polarizers of a Langmuir-Blodgett structure on a silicon wafer and on a surf.
  In addition to visualization, recent developments have allowed accessing to the thickness measurement of the analyzed sample. A colorimetric correspondence is carried out between a calibration standard made of nano-steps and the analyzed sample. Indeed, due to optical interference, a correlation exists between RGB (red, green, blue) parameters of the sample and its optical thickness. This leads to 3D-representation of the analyzed samples, the measurement of profile sections, roughness and other topological measurements.
caption: Light polarisation after reflexion on a surf (0) and on nanoscale sample on a surf (1).
exif: {}