Oxide-based photonic crystals from biological templates

The world of insects is full of structural colors, lending butterfly wings, bird feathers, and beetle scales their strikingly iridescent appearance. Since many of the structures behind these optical effects are so-called photonic crystals, they have recently attracted the interest of optical engineers and scientists as unique structural templates. This chapter aims to discuss recent developments in replicating biological structures into oxide-based photonic crystals operating at visible frequencies. Following a brief introduction into the physics and properties of photonic crystals, this chapter will focus on the following topics: (1) recent advances and limitations of top-down and bottom-up photonic crystal engineering routes; (2) examples and properties of biological photonic crystals; and (3) conversion of biological structures into oxide-based replicas by deposition methods (atomic layer deposition and conformal-evaporated-film-by-rotation) and sol–gel chemistry routes. The chapter will conclude with an outlook on the potential of biotemplating for achieving complete photonic band gaps at visible frequencies.