Scaling of collisionally pumped 3s-3p lasers in the neon isoelectronic sequence

Abstract

Population inversions between the 3p and 3s levels of neonlike ions with atomic numbers Z=14, 18, 22, 26, 32, and 36 have been calculated. The population inversions result from the preferential population of the 3p level by electron collisional excitation from the ground configuration of the ion and occur over a wide range of electron temperature and electron density (from 10¹⁷ cm⁻³ for Si V to 10²² cm⁻³ for Kr XXVII). For all ions that are studied, the maximum value of the population inversion (N_3p/g_3p−N_3s/g_3s) for the transition 3p ¹S₀−3s ^uP₁ (where u represents the upper of the singlet and triplet levels) is found to be approximately equal to 4×10⁻³ N_I, where N_I is the total density of neonlike ions. With the exception of Si V, laser gains greater than 1 cm⁻¹ are possible for all the ions that are considered, and the gain increases with atomic number Z. For Si V and lower‐Z ions, electron collisional mixing of the upper and lower laser levels restricts the electron density at which the population inversion occurs and limits the laser gain to values less than 1 cm⁻¹. The scaling of the laser gain and the plasma parameters with atomic number Z is presented. For an electron density of 10²¹ cm⁻³, the optimum atomic number Z that results in the highest gain on the 3p ¹S₀−3s ^uP₁ transition is Z=26 (Fe XVII), and the gain is equal to 30 cm⁻¹.