Bonn 2025 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 74: Photonics II
Q 74.8: Vortrag
Freitag, 14. März 2025, 16:15–16:30, HS Botanik
Colloidal self-assembly for 3D second-harmonic photonic crystals — •Thomas Kainz1,2, Ullrich Steiner1,2, and Viola Vogler-Neuling1,2 — 1Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland — 2NCCR Bio-inspired Materials, University of Fribourg, Fribourg, Switzerland
Three-dimensional nonlinear photonic crystals can simultaneously generate different nonlinear processes, like second-harmonic generation (SHG) and other sum- and difference-frequency processes. However, creating large crystals in all three dimensions presents a considerable challenge, primarily due to the chemical inertness of metal oxides. This study shows the first demonstration of colloidal-crystal-templating into a second-order optical material. Different templates made of polystyrene opals are self-assembled from monodisperse nanospheres with tunable unit sizes. These are infiltrated with barium titanate sol-gel, which results after calcination in an inverse fcc network of tetragonal barium titanate. We fabricated samples with unprecedented sizes (above 3000 unit cells in x, y directions and 100 in z). The achieved reflectivity values are above 80 % throughout the fabrication. We can tune the final photonic bandgap over the whole optical range, matching it to material and setup requirements. We successfully replicated the photonic network into a second-order material and demonstrated, for the first time, a linear photonic band gap from a fully scalable three-dimensional photonic crystal made of a nonlinear optical material. This enables the experimental investigation of SHG within a bandgap, like inhibited spontaneous emission.
Keywords: 3D nonlinear photonic crystal; Second-harmonic generation; Inhibited spontaneous emission; Colloidal self-assembly; Polystyrene opals