Optical spectra of composite cholesteric elastomers doped with metallic nano-ellipsoids

We consider a hybrid system composed of a cholesteric elastomer and a small volume fraction of gold or silver nano-ellipsoids. One of the semi-axes of the ellipsoidal nanoparticles is aligned parallel to the helical axis of the host cholesteric medium. We calculate the effective dielectric tensor by using a generalisation of the Maxwell-Garnet formalism for uniaxial media with low birefringence, for which case the optical response can be simply described by using only two effective refraction indexes. We use this approach to obtain the co-polarised and cross-polarised transmission and reflection spectra of circularly polarised light of both handedness impinging the sample normally. We obtain these optical spectra versus the constituent parameters of the ellipsoids (size of its semiaxes) forming the guest medium and the strain parameter of the host elastomer medium.