Optical spectra for a cholesteric elastomer doped with metallic nanospheres with an inversion defect

Abstract

We are considering the propagation of circularly polarized light normally impinging on a cholesteric elastomer slab doped with metallic spheres. The slab is composed of two layers: the first layer is a right-handed chiral structure, and the second one is a helix with left-handedness; however, the pitch of the chiral structure remains constant. We performed a theoretical model to find numerically, reflection and transmission spectra for circularly polarized light impinging on the slab. We considered the effects of mechanical strains along the helical axis since the force exerted on the structure can tilt the mesogens in the slab along the helical axis. The Photonic Band-Gap(PBG) of the elastomer slab becomes narrowed because of the strain; there we also observe high reflectance (hyper-reflectivity) that depends on the filling factor of the silver doping and on whether the defect is located at a position that contains complete periods of the structure. Additionally, the spectra display reflection bands for both right- and left-polarized light. We expressed the PBG edges in terms of material parameters; this allows us to select the region of the electromagnetic spectrum for the reflection bands. This medium exhibits a hyper-reflective photonic band when the pitches of both right- and left-handed helical layers are identical.