Microscale reflectance spectrometry of thin-film structures in butterfly wing scales

Butterfly wings often feature multilayer thin-film (approximately 0.1 μm) structures within its scales known to produce optical interference responsible for iridescence. These specialized film structures may have a thermoregulatory as well as coloring function. The solar absorption of these intricate structures is a significant mode of heat transfer to the butterflies. Experimental and numerical studies are used to resolve the spectral reflectivity of these multilayer thin-film structures. An experimental apparatus was developed and used to measure the spectral reflectance from the individual scales as well as recording video images of the illuminated scales. Non-uniform film thicknesses and rib-like structures in the scales are also investigated for microscale radiative effects. Remits indicate that scales can have high total solar absorption as well as high reflection of a specific wavelength range