Ar ii laser generated by Landau damping of whistler waves at the lower hybrid frequency

Abstract

Lasing of the 488-nm Ar i i line has been demonstrated in the central 1.2 cm of a 4.5-cm diam rf-produced magnetoplasma at pressures of 1 Pa. The external rf antenna excites an m=1 whistler wave at the lower hybrid launch frequency which produces a highly ionized plasma. The inferred population inversion and the correspondence between measured wave phase velocity and the upper energy levels of the observed transitions suggest that Landau damping of the wave can selectively distort the electron distribution function at an energy equivalent to the phase velocity of the wave.