Terahertz Anglular Distribution from Single-Color Filament Plasma at Various Laser Beam Numerical Apertures.

The angular distributions of various spectral components of terahertz radiation generated by filament plasma are measured in a wide range of numerical apertures NA of the laser beam from 0.003 to 0.1. It is shown that propagation angles of terahertz radiation are inversely proportional to the square root of the terahertz frequency. It is shown that an increase in the numerical aperture of the laser beam leads to an increase in propagation angles of terahertz radiation in the entire range of observed frequencies. [ABSTRACT FROM AUTHOR]