Beetle Teaches Photonics

Scientists have discovered that the spectacular green color of the jeweled beetle Chrysina gloriosa stems from the complex structure of the cells of its exoskeleton, which bear geometric resemblance to some types of synthetic liquid crystals (Science 2009, 325, 449). This insight from biology should help scientists in the "quest for miniature optical devices and photonics," writes the research team, which was led by Mohan Srinivasarao of Georgia Institute of Technology. The researchers observed that the beetle's green reflection occurs only when it's exposed to either unpolarized light, such as sunlight, or left circularly polarized light. When exposed to right circularly polarized light, the beetle takes on a dull brown hue. Using confocal microscopy, the group found that the source of this characteristic reflectivity lies in the beetle's mostly hexagonal-shaped exoskeletal cells. Each cell consists of a series of nested arcs that circle a cone at its center. These structures resemble the spontaneously formed defect structures on the free surface of chiral nematic liquid crystals.