AVS 58th Annual International Symposium and Exhibition
    Spectroscopic Ellipsometry Focus Topic Thursday Sessions
       Session EL+AS+EM+MS+PS+TF-ThM

Paper EL+AS+EM+MS+PS+TF-ThM4
The White Scarab Beetle Cyphochilus insulanus –Scattering and Polarization Properties

Thursday, November 3, 2011, 9:00 am, Room 209

Session: Spectroscopic Ellipsometry of Biological Materials and Organic Films
Presenter: Christina Akerlind, Swedish Defence Research Agency / Linköping University, Sweden
Authors: C. Akerlind, Swedish Defence Research Agency / Linköping University, Sweden
H. Arwin, Linköping University, Sweden
T. Hallberg, Swedish Defence Research Agency, Sweden
H. Kariis, Swedish Defence Research Agency, Sweden
J. Landin, Linköping University, Sweden
K. Järrendahl, Linköping University, Sweden
Correspondent: Click to Email
Three methods were used to characterize the optical properties of the light scattering white scarab beetle Cyphochilus insulanus. Spectral directional hemispherical (DH) reflectance measurements in the wavelength region 250 nm to 25 µm were performed using integrating spheres. The general spectral appearance shows a relatively strong reflectance band in the range 400 ‑ 1600 nm. The Bidirectional Reflection Distribution Function (BRDF) was measured over a semi-circle in the plane of incidence at the wavelengths 633 nm and 3.39 µm, using s- and p-polarized light. In the visible the BRDF data shows a near Lambertian behaviour with a constant BRDF for most angles, i.e. the light is diffusely scattered. For large incident angles and in the infrared the BRDF is more specular. Full Mueller-matrix spectroscopic ellipsometry (MMSE) measurements were performed in the wavelength range 250 - 1000 nm at angles of incidence between 45° and 75° using a dual rotating compensator ellipsometer. The Mueller data show that the reflected light in general has a high degree of polarization P even for nonpolarized incident light. The angular dependence of P was pronounced for incident p-polarized light and was very low near the Brewster angle. In comparison, P was high for all measured angles for incident s-polarized light. Close to the Brewster angle, the reflected light showed a high ellipticity for incident p-polarized light. The optical data is used to model the structure and optical response of the beetle cuticle. With input from the DH and BRDF-data analysis of the Mueller Matrix data was made using Fresnel-based layer modelling. 2-, 3- and n-phase models are compared. The obtained optical properties are also used to calculate color data in terms of chromaticity and whiteness. The scattering properties of the Cyphochilus insulanus cuticle are also discussed by combining the BRDF and MMSE data as well as recently obtained Mueller matrix imaging polarimetry results.