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Optical properties of diatom nanostructured biosilica in Arachnoidiscus sp: micro-optics from mother nature.

Ferrara MA, Dardano P, De Stefano L, Rea I, Coppola G, Rendina I, Congestri R, Antonucci A, De Stefano M, De Tommasi E - PLoS ONE (2014)

Bottom Line: This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous silica, called frustule.We found photonic effects due to diffraction by ordered pattern of pores and slits, accordingly to an elaborated theoretical model.Characterization of such intricate structures can be of great inspiration for photonic devices of next generation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Microelectronic and Microsystems, Department of Naples, National Research Council, Naples, Italy.

ABSTRACT
Some natural structures show three-dimensional morphologies on the micro- and nano-scale, characterized by levels of symmetry and complexity well far beyond those fabricated by best technologies available. This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous silica, called frustule. We have studied the optical properties of Arachnoidiscus sp. single valves both in visible and ultraviolet range. We found photonic effects due to diffraction by ordered pattern of pores and slits, accordingly to an elaborated theoretical model. For the first time, we experimentally revealed spatial separation of focused light in different spots, which could be the basis of a micro-bio-spectrometer. Characterization of such intricate structures can be of great inspiration for photonic devices of next generation.

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Related in: MedlinePlus

Intensity maps obtained by Digital Holography at λ = 632.8 nm at different distances along the optical axis: a) in the focus plane (z = 0 µm); b) and c) forward the focus plane (z = 71.2 µm and z = 437.3 µm).Light confinement occurs in a zone along the optical axis corresponding to the center of the diatom. d): intensity profiles obtained at different distances along the optical axis in the focus plane (z = 0 µm, blue line) and forward the focus plane (z = 71.2 µm, red line; z = 437.3 µm, green line).
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pone-0103750-g009: Intensity maps obtained by Digital Holography at λ = 632.8 nm at different distances along the optical axis: a) in the focus plane (z = 0 µm); b) and c) forward the focus plane (z = 71.2 µm and z = 437.3 µm).Light confinement occurs in a zone along the optical axis corresponding to the center of the diatom. d): intensity profiles obtained at different distances along the optical axis in the focus plane (z = 0 µm, blue line) and forward the focus plane (z = 71.2 µm, red line; z = 437.3 µm, green line).

Mentions: The reconstructed intensity profile of the valve is reported in Figure 9 (a–c). Digital Holography (DH) allows the reconstruction of the transmitted intensity field along z-direction by means of a proper numerical algorithm (for analytical details see equation (11) in Methods). Only one hologram has been acquired and then the reconstructed field was propagated with a scanning pitch of ≈λ/20 along z direction, thus giving a more resolved characterization of the z-propagation with respect to typical measurements which require acquisition of series of images at different positions along the optical axis by means of a microscope objective (see Ref. [18]–[20] and previously shown measurements). By using the aforementioned algorithm, the reconstructed optical wave field has been propagated at different distances. In Fig. 9 reconstructions of the light transmitted by the diatom valve in air at two different distances are reported: z = 71.2 µm (b), z = 437.3 µm (c). Light confinement occurs, along z direction, in correspondence of the center of the diatom and eventually also a light ring appears, probably due to the diffraction from valve edges and costae. The intensity profiles at y = 163 µm (along the diameter of the valve), at all the three distances considered, are showed in Fig. 9d. The Full Width at Half Maximum (FWHM) of the spot is 9.2 µm at z = 71.2 µm, and 10.1 µm at z = 437.3 µm. In these measurements, the incident beam is expanded up to 1 cm diameter, collimated and then directed on the frustule: the coherent light is thus squeezed by a factor greater than 1000.


Optical properties of diatom nanostructured biosilica in Arachnoidiscus sp: micro-optics from mother nature.

Ferrara MA, Dardano P, De Stefano L, Rea I, Coppola G, Rendina I, Congestri R, Antonucci A, De Stefano M, De Tommasi E - PLoS ONE (2014)

Intensity maps obtained by Digital Holography at λ = 632.8 nm at different distances along the optical axis: a) in the focus plane (z = 0 µm); b) and c) forward the focus plane (z = 71.2 µm and z = 437.3 µm).Light confinement occurs in a zone along the optical axis corresponding to the center of the diatom. d): intensity profiles obtained at different distances along the optical axis in the focus plane (z = 0 µm, blue line) and forward the focus plane (z = 71.2 µm, red line; z = 437.3 µm, green line).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4116236&req=5

pone-0103750-g009: Intensity maps obtained by Digital Holography at λ = 632.8 nm at different distances along the optical axis: a) in the focus plane (z = 0 µm); b) and c) forward the focus plane (z = 71.2 µm and z = 437.3 µm).Light confinement occurs in a zone along the optical axis corresponding to the center of the diatom. d): intensity profiles obtained at different distances along the optical axis in the focus plane (z = 0 µm, blue line) and forward the focus plane (z = 71.2 µm, red line; z = 437.3 µm, green line).
Mentions: The reconstructed intensity profile of the valve is reported in Figure 9 (a–c). Digital Holography (DH) allows the reconstruction of the transmitted intensity field along z-direction by means of a proper numerical algorithm (for analytical details see equation (11) in Methods). Only one hologram has been acquired and then the reconstructed field was propagated with a scanning pitch of ≈λ/20 along z direction, thus giving a more resolved characterization of the z-propagation with respect to typical measurements which require acquisition of series of images at different positions along the optical axis by means of a microscope objective (see Ref. [18]–[20] and previously shown measurements). By using the aforementioned algorithm, the reconstructed optical wave field has been propagated at different distances. In Fig. 9 reconstructions of the light transmitted by the diatom valve in air at two different distances are reported: z = 71.2 µm (b), z = 437.3 µm (c). Light confinement occurs, along z direction, in correspondence of the center of the diatom and eventually also a light ring appears, probably due to the diffraction from valve edges and costae. The intensity profiles at y = 163 µm (along the diameter of the valve), at all the three distances considered, are showed in Fig. 9d. The Full Width at Half Maximum (FWHM) of the spot is 9.2 µm at z = 71.2 µm, and 10.1 µm at z = 437.3 µm. In these measurements, the incident beam is expanded up to 1 cm diameter, collimated and then directed on the frustule: the coherent light is thus squeezed by a factor greater than 1000.

Bottom Line: This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous silica, called frustule.We found photonic effects due to diffraction by ordered pattern of pores and slits, accordingly to an elaborated theoretical model.Characterization of such intricate structures can be of great inspiration for photonic devices of next generation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Microelectronic and Microsystems, Department of Naples, National Research Council, Naples, Italy.

ABSTRACT
Some natural structures show three-dimensional morphologies on the micro- and nano-scale, characterized by levels of symmetry and complexity well far beyond those fabricated by best technologies available. This is the case of diatoms, unicellular microalgae, whose protoplasm is enclosed in a nanoporous microshell, made of hydrogenated amorphous silica, called frustule. We have studied the optical properties of Arachnoidiscus sp. single valves both in visible and ultraviolet range. We found photonic effects due to diffraction by ordered pattern of pores and slits, accordingly to an elaborated theoretical model. For the first time, we experimentally revealed spatial separation of focused light in different spots, which could be the basis of a micro-bio-spectrometer. Characterization of such intricate structures can be of great inspiration for photonic devices of next generation.

Show MeSH
Related in: MedlinePlus