Naturally sourced photonic and plasmonic crystals derived from diatom frustules

Diatoms are an abundant group of algae, sharing a unique feature; they produce silica exoskeletons featuring intricate nanostructures, known as a frustule. In certain species this includes a porous network with high precision lattices, strongly resembling photonic crystals produced using modern technological processes. Here we show two means for using these frustules as an optical material. Firstly, the unprocessed frustule can be used as a conventional photonic crystal. Secondly, a metal deposition processing step can yield plasmonic crystals. Both show high quality optical properties, analogous to lab-manufactured structures, and are produced over much larger areas at a much lower cost and without specialist equipment. Optical spectra (angularly resolved dispersions) are presented, along with simulation results to corroborate experimental findings and to allow optical mode characterisation and analysis.