Transients in chiral media with single-resonance dispersion

Abstract

We study theoretically the propagation of a transient electromagnetic pulse in an unbounded homogeneous, isotropic, reciprocal, chiral medium, using the standard Fourier transform technique. We assume linear, causal, dispersive chiral media with single-resonance dispersion. For the permittivity and permeability functions a single-resonance Lorentz model is assumed, and for the chirality admittance function a single-resonance model consistent with Condon’s model of optical activity is used. Propagation of a TEM plane wave of a step sinusoidal signal is considered. We analyze the transient behavior of the electric-field components at a distant location and at various times of observation. In particular the role of the chirality of the medium and its effects on the dynamical evolution of the transient pulse in such a medium are highlighted, and the similarities and the differences between the transient signal propagation in chiral and nonchiral dispersive media are investigated. We show that several novel phenomena result from the presence of chirality in the medium. Among them are the development of a cross-polarized component, the splitting of instantaneous frequency (which suggests that there are effectively two first precursors and two second precursors for each field component of the transient pulse), and the buildup of the main signal in two stages. Other notable effects are also discussed. Physical insights into these results are provided.