Transition radiation at the boundary of a chiral isotropic medium.

This study analyzes the radiation produced by a point charge intersecting the interface between a vacuum and a chiral isotropic medium. We deduce analytical expressions for the Fourier components of an electromagnetic field in both vacuum and medium for arbitrary charge velocity. The main focus is on investigating the far field in a vacuum. The distinguishing feature of the interface with a chiral isotropic medium is that the field in the vacuum area contains both copolarization (coinciding with the polarization of the self-field of a charge) and cross-polarization (orthogonal to the polarization of the self-field). Using a saddle-point approach, we obtain asymptotic representations for the field components in the far-field zone for typical frequency ranges of the Condon model of the chiral medium. We note that a so-called lateral wave is generated in a vacuum for certain parameters. The main contribution to the radiation at large distances is presented by two (co- and cross-) spherical waves of transition radiation. These waves are coherent and result in a total spherical wave with elliptical polarization, with the polarization coefficient being determined by the chirality of the medium. We present typical radiation patterns and ellipses of polarization.

Electromagnetic field of a charge moving in a chiral isotropic medium.

We analyze the electromagnetic field generated by a point charge moving with a constant velocity in an isotropic chiral medium. We work in the frame of the Condon dispersion model for the weak chirality and ultrarelativistic motion of the charge. We show that the field of a moving charge contains two low-frequency wave processes with right- and left-hand circular polarizations and a high-frequency wave process with a right-hand polarization. The low-frequency wave field exists at an arbitrary charge velocity and oscillates at a frequency of the order of the resonant frequency of the medium. This effect is of most importance near the charge trajectory. The high-frequency wave field arises at an ultrahigh velocity and is essential near the plane of charge dislocation for a sufficiently large offset from the trajectory. This wave field oscillates at a frequency that is considerably greater (up to several orders) than the resonant frequency of the medium. Intriguingly, both of these phenomena exist in the domain in front of the charge, thus producing the low- and high-frequency wave forerunners correspondingly.