Absorption line narrowing (A.L.N.) in a three-level system of neon under interaction with two quasi-resonant lasers

We report the observation of Absorption Line Narrowing (A.L.N.) in a Doppler-broadened three-level system of neon under interaction with two quasi-resonant single-mode lasers. The resonance signals are obtained with the laser beams propagating either in the same direction or in opposite direction. The resonance width is found to be smaller in the latter case. The isotopic shifts ²²Ne-²⁰Ne of the lines λ = 1.15μ, λ = 6096 Å and λ = 5945 Å have been measured using the A.L.N. method.