Crossed polarization optical transmittance spectra as a way of determining wing thickness of the Episcada Hymenaea translucent butterfly

The accurate determination of sample thickness is crucial for its comprehensive characterization in materials science. Interference oscillations in optical spectra offer a simple method to achieve this, relying on the sample's preservation of light coherence. However, conventional spectra may fail to exhibit these oscillations in numerous samples due to factors such as high transparency, anisotropy, or scattering caused by nanostructures. In this study, we implement a crossed polarization spectral transmittance measurement which successfully unveils hidden interference oscillations by exploiting the polarization conversion characteristics in the wing of the Episcada hymenaea translucent butterfly. We compare the thickness measurements obtained using this method with those derived from Scanning Electron Microscopy and find a relative difference as low as 5% as well as high robustness against variations in the refractive index.