Study of Threshold Condition and Population Inversion in Helium-Neon laser

Abstract

The Helium–Neon (He–Ne) laser is one of the most widely studied gas lasers due to its simple design, stable output, and well-understood atomic transition mechanisms. This study investigates the threshold condition and the mechanism of population inversion in a He–Ne laser system. The threshold condition represents the minimum pumping power required to overcome cavity losses and achieve sustained laser oscillation. In a He–Ne laser, electrical discharge excites helium atoms to metastable energy states, which subsequently transfer their energy to neon atoms through resonant collisions. This process produces a population inversion between specific excited states and lower energy levels of neon, enabling stimulated emission at the characteristic wavelength of 632.8 nm.