Spontaneous amplified emission of a Na 2 diffuse violet band produced through two-photon excitation of sodium vapor

Abstract

We report observation of enhanced emission of the diffuse violet band at 436.0 nm when sodium vapor is optically pumped with a pulsed dye laser with output wavelength in the 570–595 nm region. A significant enhanced emission is observed in the forward direction along the propagating laser beam when the laser wavelength is tuned to near the two-photon excited 4d state of the Na atom. At a vapor density higher than 10 15 cm -3 the diffuse violet emission is predominantly produced through processes associated with the excitation of Na 2. The dependence of the enhanced emission on vapor density and laser power density is presented.