CORDIS - EU research results

Multi-focal scanning plasmonic nanoscope for super resolution imaging of living cells

Final Report Summary - MULTISPLASH (Multi-focal scanning plasmonic nanoscope for super resolution imaging of living cells)

Optical super-resolution is well established reality in modern imaging techniques and has given rise to a recent Nobel Prize in chemistry. Using the photochemistry of florescent molecules, different approaches (STED, PALM, STORM) allow us today obtain images at tenth of nanometer resolution. Yet, the super-resolution of these approaches is often accompanied by limitations in other imaging parameters such as the acquisition time or the field-of view. The need for an imaging technique that is robust not only in resolution but also in other parameters has motivated, among others, the development of this project.

This projects aims at developing an alternative imaging technique which can provide optical super-resolution using novel principles from nanophotonics. The main objectives of the proposal are focused towards an imaging technique that offers:
1. Large field-of-view
2. Fast acquisition time
3. Optical super-resolution
4. Biological relevance

The main idea of this project is to achieve super-resolution via confining light to a metal-dielectric interface. Metal-dielectric interfaces support plasmonic modes that propagate along the interface with a wavelength shorter than light. The smallest size to which light can be focused is determined by the wavelength in what is known as the diffraction limit. Therefore, shortening the light wavelength using surface wave would allow us to scale this limit below 100 nanometers and provide nanoscopy.

Our first results (Nano Letters 2014) showed that using a thin Silicon-nitride membrane coated with Silver allowed us to create a two dimensional platform that supported optical modes with a wavelength more than two times shorter than that of the light in air. These results showed a scaled diffraction limit of nearly 110 nanometers which is better than the resolution typically used for imaging in biology, medicine or industry. Following on this super-resolution, we implemented a methodology that allows for fast imaging. Specifically, by creating and observing fringes of light in this short wavelength platform we demonstrated (Applied Physics Letters 2015) compatibility with structured illumination microscopy (SIM) that allows for fast imaging and the possibility of a large field-of-view.

Aiming to optimal super-resolution capabilities we successively developed a photonic-plasmonic platform that would enhance the resolution even further and add extra technological benefits. Namely by utilizing a Silicon film we provided super-resolution on a chip which can be used to merge on a single platform electronics and photonics. Using the refractive index of Silicon we reduced the wavelength of light on such a chip by four times resulting in a greatly scaled diffraction limit. These Silicon-based lenses (Optica 2015) are capable to focus light down to a spot of nearly 60 nanometers and allow for a very high degree of control. In fact the size, and shape of such foci could be controlled at will resulting, for example, in the smallest optical vortex reported (Physical Review B - Rapid Communication 2016). Optical vortices on such a nanoscale might provide relevant for future quantum optics applications. At the actual stage (publication in preparation) we upgraded the platform so as to be also fully compatible with the semiconductor technology used to manufacture most electronics chips, namely CMOS compatibility.

In the last stage of this project we assembled the information acquired in the previous stages in an optimal microscopy design that can fulfill all objectives. We concluded that such optimal designed should be based on creating and scanning multiple fringes of light in a short wavelength platform. These results, supported by numerical calculations, have been recently accepted in Optics Letters (to be published) and are being currently filed for a patent application.

To summarize, the research performed during this project has provided progress beyond the state-of-the-art in microscopy by: (a) the development of a planar lens that can achieve super-resolution using visible light, (b) the implementation of such a lens in an industrially relevant platform such as the silicon technology, (c) the concept of a new super-resolution microscopy that provides no major limitation.

The results achieved in this project have the potential to provide new biomedical developments and to merge electronics and photonics, and hold both scientific and socio-economical relevance. A large number of high impact publications in journals from three main scientifically societies (chemistry, physics and optics) highlight the quality of the works performed as well as its interdisciplinary nature. The submission of a patent application is a clear indication of transferring knowledge from academia to industry with the potential to provide applications. The foreseen applications will be beneficial to the broad public either directly by the implementation of more advanced biomedical technology that will improve public health, or indirectly via the development of commercial enterprises which will improve the job market and the competitively of the related products. The experience acquired during this project, in terms of scientific excellence, leadership and managment, and IP rights, has allowed the development of the researcher and facilitated his career advancement in academia or industry.

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