Optimum electromagnetic wave excitations of complex media characterized by positive or negative refractive indices and by chiral properties

摘要

The chiral properties of naturally occurring biological or chemical threat agents are usually weak, and the expressions in the constitutive relations associated with charility are relatively small compared with the familiar terms associated with the electric permittivity and magnetic permeability of the medium. Therefore it is necessary to optimize the excitation of the chiral materials in order to detect and identify the threat agents. Moreover chiral materials characterized by positive or negative refractive indices have several novel applications in nanophotonics. For these nanophotonic devices to perform efficiently, it is also necessary to optimize the excitation of these devices. Since the Mueller matrices that relate the scattered to the incident Stokes vectors completely characterize scattered polarized electromagnetic waves, much attention is given to the explicit expressions for the reflection and transmission matrices that also account for the cross-polarized coefficients. To first order, the cross-polarized coefficients are proportional to the chiral parameter. It is therefore important to determine the relationships between the cross-polarized coefficients and the incident angle of excitation, the medium parameters (such as the refractive index and the intrinsic impedance of the achiral host medium), and the wavelength. The optimum polarization and the mode of operation (reflection or transmission) are also important factors that need to be determined. (c) 2007 Optical Society of America.