Séminaire PMMH - Serge Berthier (INSP)

6 janvier 2023 11:00 » 12:00 — Salle réunion PMMH 1

Natural Photonics

Photonics, the art of manipulating light, is a relatively recent science. To manage light, to confine it, to slow it down, to orient it... you have to put yourself on its scale, that of the wavelength, that is to say, to create periodic structures (like an electromagnetic wave) who’s the period is of the order of a few tenths of the wavelength. Typically for the visible : 50 to 100 nm. We are stammering in this area, but many living organisms, mainly arthropods, because of their large number, but also birds, reptiles, fish, etc. have developed such structures, called "photonic crystals", to manage their interactions with the various sources of electromagnetic radiation to which they are subjected. From ultraviolet to thermal infrared, we will show various examples of light-insect interactions in each of these areas : Fluorescence and UV protection ; physical colours, colour change in the visible, perception and production of polarization light ; thermal management and detection in infrared range.
What does this research tell us :
 That a “good” structure is always multifunctional (a butterfly wing is only used incidentally to fly !).
 That this structure is optimized on average (No function is privileged over the others)
 That it is extremely economical in terms of chemical elements (Most structures only use 4 to 5 elements of the periodic table).

Such achievements can only be obtained thanks to the structural complexity (which overcomes the economy of elements) and a controlled degree of disorder which ensures the average optimization of the structure and its multifunctionality. If we do not know how to control disorder, we can measure it. We’ll see how.

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