Conical Forward THz Emission from Femtosecond-Laser-Beam Filamentation in Air

Abstract

We attribute a strong forward directed THz emission from femtosecond laser filaments in air to a transition-Cherenkov emission from the plasma space charge moving behind the ionization front at light velocity. Distant targets can be easily irradiated by this new source of THz radiation.

Experimental observation of a traveling plasma grating formed by two crossing filaments in gases

“…This nonlinear propagation process has attracted many research interests. The reason is not only the rich physics involved, but also its various potential applications, such as remote sensing of atmospheric pollution [3], pulse compression down to few cycle regime [4], triggering and guiding of electric discharge [5], remote THz pulse generation [6], to name a few. In the last few years, the interaction of two filaments in gases and solids has triggered new research interests [7][8][9][10][11][12][13].…”

Angular width of the Cherenkov radiation with inclusion of multiple scattering

“…Conical forward THz emission from femosecond-laser-beam filamentation in air is also partially attributed to Cherenkov radiation by some authors [4]. For the case of simplicity, the motion of electrons is usually assumed uniform [5].…”

Detection of the polarization spatial distribution of THz radiation generated by two-color laser filamentation

“…Filamentation deserves attention because it allows the generation of high-intensity THz radiation and management of its properties (intensity, polarization and radiation pattern) by varying the pump pulse duration and focusing conditions [12,13]. The physical origin of the THz radiation is attributed to the transition Cherenkov emission process [14,15]. One of the important properties of THz radiation is the polarization state.…”

“…One of the important properties of THz radiation is the polarization state. Previously [14,16], it has been shown that the integrated field of the THz beam has a radial polarization. In the latest research, these results have been supplemented with the fact that the polarization of the THz field has an elliptic structure [17,18].…”