Quantitative readout of optically encoded gold nanorods using an ordinary dark-field microscopeElectronic supplementary information (ESI) available: Experimental setup and sample preparation. See DOI: 10.1039/c3nr00726j

In this paper we report on a new use for dark-field microscopy in order to retrieve two-dimensional maps of optical parameters of a thin sample such as a cryptograph, a histological section, or a cell monolayer. In particular, we discuss the construction of quantitative charts of light absorbance and scattering coefficients of a polyvinyl alcohol film that was embedded with gold nanorods and then etched using a focused mode-locked Ti:Sapphire oscillator. Individual pulses from this laser excite plasmonic oscillations of the gold nanorods, thus triggering plastic deformations of the particles and their environment, which are confined within a few hundred nm of the light focus. In turn, these deformations modify the light absorbance and scattering landscape, which can be measured with optical resolution in a dark-field microscope equipped with an objective of tuneable numerical aperture. This technique may prove to be valuable for various applications, such as the fast readout of optically encoded data or to model functional interactions between light and biological tissue at the level of cellular organelles, including the photothermolysis of cancer. Submicron-resolved mapping of optical absorbance and scattering is achieved by the comparison of dark-field and bright-field micrographs, which is illustrated with a pattern of gold nanoparticles in polyvinyl alcohol. This method may serve to inspect samples such as cryptographs, histological sections and cell monolayers.