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Multiscale Optical imaging of complex fields based on the use of azobenzene nanomotors


The ability to image the optical near-field intensities that result when nanostructured materials and devices are exposed to light is essential for both advancing scientific knowledge and for enabling applications. Since ordinary optical microscopy cannot resolve beyond about a half wavelength of visible light, other approaches that go beyond this diffraction limit must be used, such as scanning near-field optical microscopy (SNOM) and photoemission electron microscopy (PEEM). We study experimentally and theoretically the optical near-fields produced by metal nano-particles under a variety of illumination conditions through photochemical imaging. Our non-invasive method relies on the optically induced vectorial molecular mass transport of a light sensitive copolymer. The experimental and theoretical results clearly show that this method can map the three spatial components of the optical near-field of complex metal nanostructures. The method was applied to map the electromagnetic near-field of various metal nanostructures: nanorods, bowties, nanocubes… In particular, in the case of the bowtie we find that longitudinally polarized plasmons are confined at the top of the metallic structures. Furthermore, the intricate optical near-fields in the polymer lead to molecular trapping regions at intensity minima as clearly demonstrated experimentally and theoretically. In parallel, we developed a model based in the probability of absorption by the azo-molecule. Moreover, various hypothesis are made in order to take into account the polymer matrix.The statistical model-based Monte Carlo method shows good agreement with far-field and near-field observations. Using the complex calculated electromagnetic field, we mimic the experimentally obtained topography showing the predictive aspect of our model. We show that our method of photochemical imaging allows for mapping the optical near field of complex metal nanostructures. Moreover, we show that the model we developed is a very good predictive tool allowing us to numerically map the expected topographies induced by photoactivated molecular mass motion.
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Dates and versions

hal-02888448 , version 1 (03-07-2020)


  • HAL Id : hal-02888448 , version 1


Jerome Plain. Multiscale Optical imaging of complex fields based on the use of azobenzene nanomotors. 9th Asian Photochemistry Conference (APC 2016), Dec 2016, Singapore, Singapore. ⟨hal-02888448⟩


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