Nonlinear nanohole arrays made by combining sol-gel chemistry and soft nanoimprint lithography
High aspect ratio nanostructures in metal-oxides are challenging to produce using top-down fabrication techniques.
Here, we introduce soft-nanoimprint lithography as a scalable and simultaneously nm-precise fabrication technique for nanohole arrays in barium titanate. Our nanohole array exhibits an optical bandgap in the infrared as well as a strong resonance in the near-infrared.
The sol-gel-derived barium titanate films form polycrystalline structures with non-centrosymmetric crystal domains that enable second harmonic generation. The increased optical field confinement within the imprinted resonant nanostructures further enhances the frequency doubling efficiency by an order of magnitude. Our approach therefore combines increased nonlinear efficiencies with scalability, yielding a promising platform for flat nonlinear optical components.
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