Narrow and contrast resonance of increased absorption in Λ-system observed in Rb cell with buffer gas

International audience; We report observation of a narrow (sub-natural) and high-contrast resonance of increased absorption (“bright” resonance) in Rb cell with Ne buffer gas under previously unexplored experimental conditions for coupling and probe radiation configuration. The coupling laser-stabilized frequency is detuned by ~3 GHz from 5S1/2, Fg=3 → 5P3/2, Fe=2,3,4 transitions, while the probe laser frequency is scanned across these transitions. We believe the bright resonance formation, occurring when the probe laser frequency is blue-shifted from the coupling frequency by a value of the ground state hyperfine splitting, is caused predominantly by a 2-photon absorption of the probe radi…