We aim to develop multilayer structures that alternate dielectric and metallic layers with nanoscale thickness for extremely high resolution imaging and optical sensing. Such structures constitute hyperbolic metamaterials (HMMs) that can act as super-lenses with a spatial resolution of some tens of nanometers, thus well below the diffraction limit. The layered geometry and fabrication, that does not require costly lithography processes, accompanied by the use of materials like SiO2 as dielectric and Ag as metal, make this device platform suitable for integration with existing thin film technology, and therefore highly appealing for implementation in smart phones and point of care diagnostics.
The resolution of conventional optics is limited by diffraction, which allows only imaging of features that are larger than half of the wavelength of the probing light. While there are techniques to push this limit towards smaller wavelengths, like super-resolution imaging, use of deep-UV light, and optical near field probing, none of them offers a facile and low cost integration into mobile devices.
HMM structures, in principle, enable perfect imaging of nanoscale objects. At the current state of the art, only structures that work at one specific wavelength (in the UV-blue) visible range, related to a specific dielectric singularity (the epsilon-near-zero (ENZ) condition), have been realised.
The TEHRIS project will design novel multilayer systems that enable to achieve the dielectric singularity in the HMMs not only at a fixed frequency, but at a tunable wavelength within a spectral band in the visible and NIR range. To this end we will explore multiple dielectric materials and model the optical properties of the projected HMM within the effective medium theory (EMT). The structures with the desired properties will be fabricated by electron-beam evaporation, as well as atomic layer deposition of the materials and sputtering technique, and their optical properties will be measured by spectroscopic ellipsometry. With this approach, we will achieve multilayer films with only few hundreds of nanometer thickness that can function as perfect lenses, i.e. lead to a 1:1 image of nanoscale features.
The final objective of TEHRIS will be a proof of concept super-lens working at a tunable wavelength in the visible and NIR spectral range. Such films can be fabricated on surfaces with either micro- or macroscale lateral extension and therefore are extremely versatile for integration in today’s mobile systems and common electronics.