| AVS 57th International Symposium & Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Friday Sessions |
| Session EL+AS+EM+MS+TF-FrM |
| Session: | Spectroscopic Ellipsometry - Inorganic Thin Films |
| Presenter: | H. Arwin, Linköping University, Sweden |
| Authors: | H. Arwin, Linköping University, Sweden S. Manhas, LPICM, CNRS, Ecole Polytechnique, France J. Landin, Linköping University, Sweden K. Järrendahl, Linköping University, Sweden A. De Martino, LPICM, CNRS, Ecole Polytechnique, France |
| Correspondent: | Click to Email |
Many scarab beetles exhibit astonishing structural colors and polarization phenomena including circular polarization in the reflected light. Electron microscopy studies reveal that the cuticles of these beetles contain complex layered and/or chiral structures. From an applications point of view it is of large interest to explore these nanostructures as inspiration for biomimetic design based on structural colors and/or polarization.
In this work, spectroscopic ellipsometry as well as imaging polarimetry are used to determine normalized Mueller matrices of cuticles of several scarab beetle species. Mueller-matrix data in the visible spectral range are measured with a dual-rotating compensator ellipsometer. In addition real-space as well as Fourier-space Mueller-matrix images are recorded at 532 nm and 632 nm with an imaging polarimeter utilizing a microscope objective with a high numeric aperture.
The M41 Mueller-matrix element measured on the partly blue and partly green Coptomia laevis is very small and represents a beetle with a nanostructure without chirality. Anoplognathus frenchi is goldish and has a broad-band reflection with large values on M41. Very pronounced left-handed polarization effects are observed. Cetonia aurata has a narrow-band reflection and the color varies from green to red among species. In the color range of reflection, strong left-handed polarization is observed. Some beetles are also found to reflect right-handed polarization at certain wavelengths and angles of incidences.
The real-space Mueller-matrix images carry information about lateral variation of Mueller-matrix elements. In many cases beetle surfaces are laterally inhomogeneous. On the other hand, Fourier space images provide the azimuthal and angle of incidence variations of the Mueller-matrix elements, averaged over the spatial inhomogeneities. The Mueller-matrix images are found to be consistent with the spectroscopic Mueller-matrix results and provide complementary information. The spectral Mueller-matrix data are also used for modelling the nanostructure of beetle cuticles involving dielectric surface layers and heliocoidal structures. Parameterization in terms of layer thicknesses, refractive indices and pitch of the helix in cuticle structures are presented.