Radiation of a Solitary Polarization Pulse Moving at the Speed of Light

Abstract

Photons have zero rest mass and always travel at the speed of light in a vacuum, but have no dipole moment. Atoms and molecules, which may have a constant or variable dipole moment, have mass and therefore cannot move at or above the speed of light. As a result, the radiation from such systems moving at the velocity of light was not considered. However, it is possible to create many artificial objects (light spots, effective charges, current pulses, etc.) that can travel at the speed of light and even exceed it. In this case, they become a source of electromagnetic radiation. In this work, the radiation of a solitary polarization pulse that travels at the speed of light and has a variable or constant amplitude is discussed. It is shown that if the amplitude does not change, then such an object does not radiate outward, i.e., the field emitted by it remains completely localized inside the moving polarization pulse. If the amplitude changes over time, then it begins to radiate backwards. In this case, unipolar pulses of an unusual shape, such as a rectangular one, can be obtained.

Dynamics of microcavities created by nonharmonic unipolar light pulses in a resonant medium

“…In the optical region, fast electron acceleration in a foil target [19], Fourier synthesis of broadband pumping [20] or the attosecond light field synthesizer [21] can be used to generate half-cycle attosecond pulses with a strong half-wave of one polarity. It was shown that unipolar pulses of rectangular or other non-harmonic shape can be obtained both in the terahertz and optical range [16,[22][23][24][25][26][27][28]. One of the possible applications of extremely short pulses (ESPs) is creating and controlling gratings of population difference n and formation of polarization waves, when pulses interact coherently with a medium [29-31], i.e., when the interaction time of pulses with a medium (pulse duration τ and delay between them Δ) is much shorter than the relaxation times of the population difference 𝑇 1 and polarization 𝑇 2 .…”