Highly Reproducible, Bio‐Based Slab Photonic Crystals Grown by Diatoms

Abstract

Slab photonic crystals (PhCs) are photonic structures used in many modern optical technologies. Fabrication of these components is costly and usually involves eco‐unfriendly methods, requiring modern nanofabrication techniques and cleanroom facilities. This work describes that diatom microalgae evolved elaborate and highly reproducible slab PhCs in the girdle, a part of their silicon dioxide exoskeletons. Under natural conditions in water, the girdle of the centric diatom Coscinodiscus granii shows a well‐defined optical pseudogap for modes in the near‐infrared (NIR). This pseudogap shows dispersion toward the visible spectral range when light is incident at larger angles, eventually facilitating in‐plane propagation for modes in the green spectral range. The optical features can be modulated with refractive index contrast. The unit cell period, a critical factor controlling the pseudogap, is highly preserved within individuals of a long‐term cultivated inbred line and between at least four different C. granii cell culture strains tested in this study. Other diatoms present similar unit cell morphologies with various periods. Diatoms thereby offer a wide range of PhC structures, reproducible and equipped with well‐defined properties, possibly covering the entire UV‐vis–NIR spectral range. Diatoms therefore offer an alternative as cost‐effective and environmentally friendly produced photonic materials.

Subsurface Chlorophyll-a Maxima in the Southern Ocean

“…Diatoms efficiently use nutrients, due to their ability to take up nutrients rapidly and maintain large nutrient reserves (Lomas and Glibert, 2000;Litchman et al, 2006;Villareal, 2013, 2018;Hansen and Visser, 2019). This coupled with adaptions to low-light environments -including optimized photosystems and photonic crystals that enhance light harvesting -allows large diatoms to be active producers in the pycnocline which receives pulses of nutrients via internal waves (Holligan et al, 1985;Kemp and Villareal, 2013;Strzepek et al, 2019;Goessling et al, 2020).…”

“…While their growth may be light limited for long periods, diatoms are a form of new production with a high downward carbon export efficiency. Their unique photosynthetic apparatuses have large light harvesting complexes, enhancing their ability to photosynthesize at <1% surface light (Parslow et al, 2001;Tripathy et al, 2015;Goessling et al, 2020). These light levels are extremely low and would halt primary production for most species of phytoplankton.…”

Frontiers of light manipulation in natural, metallic, and dielectric nanostructures

“…Reproduced with permission from Ref. [78] of several diatom species presents optical activity, being able to change the state of polarization of the incident radiation; some diatoms of the genus Actinocyclus switch from one color distribution to the complementary one as the mode of illumination changes from bright field to dark field.…”

“…Chloroplasts indeed tend to locate close to the frustule walls under dim lighting conditions, thus well within the evanescent field. The photonic properties of C. granii girdles seen as photonic crystal slabs have been further deepened by Goessling et al [67,78] by means of an accurate SEM morphological characterization, 3D numerical simulations based on FDTD calculations and measurements of their photonic properties in in-plane direction by means of microscatterometry (see Fig. 8), both in air and in water.…”

Development and Optimization of Experimental Biosensing Protocols Using Porous Optical Transducers

“…Additionally, they also reported a new feature: the silica walls of both the valves and the girdle bands are not solid, but rather they have a nanoporous structure in addition to the macropores. [173].…”