Question

Discuss why nature may have evolved photonic crystals in some animals rather than using pigments, and the likely limitations of natural rather than artificial photonic crystals.

Answer 1

Answer :-

A deeper population of species with larger photonic crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection.

Photonic Band Gap crystals are generally taylor-made for present applications. They are designed and fabricated to work at a certain frequency, the central, or mid band frequency. The range of frequencies around the central frequency over which the crystal will continue to operate defines the operational bandwidth of the crystal. At present the best band widths that have been achieved represent 20-30% of the centre frequency. Once outside this operation range the photonic band gap nature is no longer seen for that particular crystal.