Ordered, quasi-ordered, and even disordered nanostructures can be identified as constituent components of several protists, plants and animals, making possible an efficient manipulation of light for intra- and inter- species communication, camouflage, or for the enhancement of primary production. Diatoms are ubiquitous unicellular microalgae inhabiting all the aquatic environments on Earth. They developed, through tens of millions of years of evolution, ultrastructured silica cell walls, the frustules, able to handle optical radiation through multiple diffractive, refractive, and wave-guiding processes, possibly at the basis of their high photosynthetic efficiency. In this study, we employed a range of imaging, spectroscopic and numerical techniques (including transmission imaging, digital holography, photoluminescence spectroscopy, and numerical simulations based on wide-angle beam propagation method) to identify and describe different mechanisms by which Pleurosigma strigosum frustules can modulate optical radiation of different spectral content. Finally, we correlated the optical response of the frustule to the interaction with light in living, individual cells within their aquatic environment following various irradiation treatments. The obtained results demonstrate the favorable transmission of photosynthetic active radiation inside the cell compared to potentially detrimental ultraviolet radiation.

The link between shape and function allows understanding the evolutionary success of several organisms and their constituent parts. This is true in particular for diatoms, unicellular microalgae which contribute massively to primary production and carbon sequestration on a global scale, and which are characterized by an impressive diversity in dimension...

Spatially disordered but uniformly distributed point patterns characterized by so-called blue-noise long-range spatial correlations are of great benefit in computer graphics, especially in spatial dithering thanks to the spatial isotropy. Herein, the potential photonic properties of blue-noise disordered, homogeneous point processes based on farthest-point optimization are numerically investigated for silicon photonics. The photonic properties of blue-noise two-dimensional patterns are studied as a function of the filling fraction and benchmarked with photonic crystals with a triangular lattice. Ultrawide and omnidirectional photonic band gaps spanning most of the visible spectrum are found with estimates of gap–midgap ratios of up to 55.4% for transverse magnetic polarization, 59.4% for transverse electric polarization, and 32.7% for complete band gaps. The waveguiding effect in azimuthal defect lines is also numerically evaluated. These results corroborate the idea that long-range correlated disordered structures are helpful for engineering novel devices with the additional degree of freedom of spatial isotropy, and capable of bandgap opening even without total suppression of infinite-wavelength density fluctuations.

Nature provides various organisms with ordered or quasi-ordered dielectric nanostructures that enable several animals, plants, and protists to manipulate light, optimizing inter- and intra-species communication, camouflage, or solar light harvesting. In particular, diatom microalgae possess nanostructured silica cell walls, known as frustules, which efficiently interact with optical radiation through multiple diffractive, refractive, scattering, waveguiding, and frequency down-conversion mechanisms. These properties contribute to diatoms’ efficiency in photosynthesis, UV tolerance, and possibly influence the phototaxis mechanisms of motile species. In our study, we utilized several imaging, spectroscopic, and numerical techniques to explore the optical functionalities of individual frustule components in the pennate, motile diatom Pleurosigma strigosum. We discuss the implications of frustule photonic properties on the living cell, and envision the exploitation of these properties in multifunctional, bio-derived photonic devices.