Polarization resolved hyperspectral imaging of the beetle Protaetia speciosa jousselini

Understanding and classifying chiral structural color of scarab beetles across the phylogenetic tree is an important scientific tool to explore the origins of the homochiral optical response in biological structures with a potential relation to the homochirality of (chitin) molecules. We report hyperspectral polarization resolved images of the scarab beetle Protaetia speciosa jousselini (Gory & Percheron, 1833) and resolve the state of polarization as a function of both position (spatial resolution of ~20 μm × 10 μm) and wavelength (spectral resolution of 5.5 nm). We observe a strong left-handed chiral Bragg reflectance and analyze the center wavelength and width of the spectrum. The reflectance and state of polarization match scale with the center wavelength of the Bragg reflection, while the relative width of reflectance spectrum is characterized by a chiral photonic strength parameter ψ ≈ 0.14 that is independent of the reflected color and position. Based on the self-similarity of the reflectance spectra we interpret variation in reflectance as variations in the thickness of the chiral Bragg reflector across the beetle.