Bio-optical structures and optical waveguides
The most advanced top-down technology for fabricating a complex optical systems falls far short when compared with the accomplishments of living organisms at ambient temperature and low pressure (and without clean rooms)71,72. Several groups have studied biomineralization in diverse marine organisms, notably the brittlestar Ophiocoma wendtii and
the sponge Euplectella. Some remarkable living optical systems have been uncovered, such as the fiber-optical spicules from Euplectella that have the dimensions of a single human hair and can act as multimode waveguides
(Fig. 4). Compared with contemporary synthetic optical fibers, the microfibers are much nanofibers), have high refractive indices and considerable flexibility, with the capacity to act as single-mode or few-mode (where light waves are effectively confined to the corer a guides when light is coupled to free-standing spicules. The enhanced refractive-index contrast between the spicule and air allows most