Mueller-matrix modeling of the architecture in the cuticle of the beetle Chrysina resplendens

Abstract

Circular Bragg reflectors have the ability of reflecting the cohanded circular-polarization mode of the inherent helicoidal structures. Cuticles of some plants and beetles are examples of natural circular Bragg reflectors. In many cases, the period or pitch of the helicoidal structure shows spatial variation across the cuticle (pitch profile). Among scarab beetles, the special architecture in the cuticle of the Chrysina resplendens comprising a birefringent layer sandwiched between two helicoidal layers reflects both right- and left-handed circular-polarization states. In this work, the modeling of Mueller-matrix data is applied to investigate polarization properties of this exceptional structure by using pitch profile and optical functions reported in the literature. Reflectance spectra for circular-polarization states are explained in terms of the phase shift introduced by the birefringent layer in a phasor plot. The azimuth-dependent polarization properties are investigated at oblique incidence for unpolarized light.