This study was aimed to investigate the formation of thin films on a nanostructured surface. Optical characterization revealed the presence of Fano-like resonance phenomenon in such single-layer structure, surrounded by a lower refractive index media. Also, we demonstrate a 5 µm thick photonic multilayer structure composed of alternating high- and low-index materials, providing angular selectivity of light. The proposed 2D structure can be considered as a promising component for intracavity spatial filtering even in high power microlasers. Moreover, the possibility to control polarization with such photonic structures will be presented.
This study was aimed to investigate the growth process of thin films on a pre-structured surface using different optically transparent materials and their optical properties. As results of conformal deposition of ion beam sputtered dense single layers on nano-modulated surfaces showed, replicability of surface modulation depends on the layer’s material itself. Among investigated metal oxides, namely tantalum, niobium, hafnium, and silicon oxides, materials with higher molecular weight tend to better repeatability of the initial structure. As an example, the surface modulation depth of tantalum oxide single layer of ~1 μm thickness has preserved almost 97 % of the initial structure, while the silica layer showed the most rapid smoothening of modulation since preserved only ~ 65 %. Considering that tantalum oxide single layers showed the best replicability results, its optical properties were investigated in a more detailed way. Optical characterization revealed the presence of Fano-like resonance phenomenon in such single-layer structure with high refractive index, surrounded by a lower refractive index media. Due to the coupling of thin film's waveguided modes with excited Fabry-Perot modes this phenomenon results in extremely low transmittance lines in the transmittance maps in a plane of the angle of incidence θ and wavelength λ. Moreover, these resonance lines show sensitivity to the angle and the wavelength of the incident light, which can serve as a demonstration of spatial and spectral filtering properties in such compact photonic single-layer structures.
In this study, we report Fano-like coupling of electromagnetic radiation to infinitely extended planar waveguiding modes of a spatially unbounded system, which specifically is a nanostructured thin film. Proposed design differs from conventional Fano-resonant systems, since conventional ones emerge from coupling to compact resonators with discrete spectrum. In this context, nanostructured thin films are explored by numerical simulations along with an analytical study, followed by the fabrication of the films by the ion beam sputtering method on nano-modulated substrates. Experimental results showed Fano-like resonances of high sensitivity to wavelength and incidence angle of the radiation. Hence, proposed design can be a potential candidate for frequency- and spatial filtering of light in transmission/reflection through/from such nanostructured thin films.
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