Abstract
We present a method for fabricating buried nanostructures by growing a dielectric cover layer on a corrugated surface profile by atomic layer deposition of TiO2. Selecting appropriate process parameters, the conformal growth of TiO2 results in a smooth, nearly flat-top surface of the structure. Such a hard surface can be easily cleaned without damage, making the nanostructure reusable after contamination. The technique has wide applicability in resonance-domain diffractive optics and in realization of quasi-planar metamaterials. We discuss design issues of such optical elements and demonstrate the method by fabricating narrow-band spectral filters based on the guided-mode resonance effect. These elements have strong potential for, e.g., sensing applications in harsh conditions.
Highlights
In a variety of optoelectronic and photonic device applications, nanostructured optical elements are expected to withstand rather extreme operating conditions
In this paper we present a fabrication technique that satisfies the requirements stated above
When this technique is used, the optical function of the element is based on the internal nanostructure underneath the essentially flat surface
Summary
Rizwan Ali[1], Muhammad Rizwan Saleem[1,2], Matthieu Roussey[1], Jari Turunen1 & Seppo Honkanen[1]. We discuss design issues of such optical elements and demonstrate the method by fabricating narrow-band spectral filters based on the guided-mode resonance effect These elements have strong potential for, e.g., sensing applications in harsh conditions. TiO2 is an excellent choice as a cover material due to its transparency over a wide spectral bandwidth, stability at high temperatures, relatively large dielectric constant, and high mechanical and chemical robustness When this technique is used, the optical function of the element is based on the internal nanostructure underneath the essentially flat surface. We illustrate the fabrication process by applying it to a particular class of nanostructured elements, i.e., Guided-Mode Resonance Filters (GMRFs)[4,5] These are narrow-band spectral filters based on guided-mode excitation anomalies in diffraction gratings with wavelength-scale periodicity, exhibiting strong reflection peaks at wavelengths that depend on the structural parameters of the grating. Experimental results are further described, and discussion and conclusions are drawn
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