Population Density Measurements of the Excited States of an Optically Excited Argon Discharge Using Emission and Absorption Spectroscopy

The populations of the excited argon 3s23p54s (s5 only) and 3s23p54p configurations in a 10 W radio frequency discharge has been studied using optical emission and diode laser absorption spectroscopy. By optically bleaching the s5→p9 transition with a narrow band laser pump of about 10 W/cm2 at 811 nm, the p9 population was increased by about a factor of 2 at a pressure of 5 Torr. At higher pressure, collisional mixing to adjacent p-states limited the laser-increased p9 population to less than 10 percent. All other laser-induced p-state populations were minimally affected at low pressure and increased by about a factor of 4 at higher pressure. The low pressure absorption line shapes exhibited an inhomogeneous hole with band-integrated absorbance that scaled linearly with pump power. The s5 population was greater than 7×1011 cm-3 at a pressure of 5 Torr, and about 57 percent of this population was moved to the p9 state at 828 mW, or about 10 W/cm2. Implications for development of a higher power optically pumped rare gas laser are discussed