Thin-film biological reflectors: optical characterization of the Chrysiridia croesus moth

The optical properties of colored wing scales of the Chrysiridia croesus moth were investigated experimentally and theoretically by reflection spectroscopy and ellipsometry. Transmission electron microscope micrographs show that the outer surfaces of these scales incorporate a fairly regular layered structure of alternating dense and less-dense material, which reflects light by the well-known thin-film interference process. A Monte Carlo-type simulation of the reflection process is discussed, which permits the determination of the complex index of refraction of the scale material.