Label Free Linear Nanoscopy

In this presentation we will show how usage of metallic free moving nanoparticles (label free) can be used for obtaining super resolved imaging in general and specifically for obtaining sub wavelength resolution and yielding the realization of linear effects based nanoscopy. The basic concept includes the conversion of the sub wavelength spatial features from evanescent waves into harmonic propagating waves by doing down conversion of the high spatial frequencies and then using the time multiplexing in order to perform the full reconstruction of the spatial-spectrum. We are using low concentration of nanoparticles having average distance being larger than the width of the imaging point spread function (PSF) which allows performing localization for the position of the moving nano-particles while having significantly sub wavelength precision for this localization. This localization precision is converted into the imaging resolution after performing the proper digital decoding process over the time varying images created from the back scattered light. In order to reduce the temporal window required for the super-resolved reconstruction, different types of nanoparticles are used (different in dimensions and in their aspect ratio) and the applied illumination contains several wavelengths and is also being modulated in time according to specific temporal sequencing. The temporal modulation of the illumination sources allows realization of a lock-in amplification of the signal to noise ratio leading to increased precision of localization even for smaller nano-particles. In addition, the time varying polarization state of the back scattered light is also examined and used to further enhance the obtainable super-resolved reconstructed image.