Theory and Design of Photonic Crystals in Broadband Biological Reflectors

In both engineering applications as well as use by living organisms, structural coloration - manipulating light using interference phenomena rather than pigments - is a common motif. Here, we will focus on the manipulation of the reflection spectra of waves using multilayered structures with two alternating indices of refraction. I will show how "chirped" structures (where the layer thickness is gradually changed throughout the structure) may lead to any reflection spectrum of choice, and how, surprisingly, disorder may be utilized to achieve certain well-defined reflection spectra, including narrow pass bands. I will compare the efficiency of chirped and disordered broadband reflectors, revealing some general principles underlying their designs.