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

TL;DR

This paper reports the observation of a narrow, high-contrast bright resonance in a rubidium cell with buffer gas, caused by two-photon absorption, and its splitting in moderate magnetic fields, expanding understanding of Lambda-system resonances.

Contribution

It introduces a new experimental configuration showing bright resonance formation in Rb with buffer gas and analyzes its splitting under magnetic fields, which was previously unexplored.

Findings

Observation of sub-natural linewidth bright resonance.

Resonance splitting into six components in magnetic fields.

Identification of two-photon absorption as the main cause.

Abstract

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 radiation 5S1/2, Fg=2 --> 5S1/2, Fg=3 with 5P3/2 as an intermediate state. We also report and interpret splitting of the bright resonance into 6 well resolved and contrast components in moderate magnetic fields (B ~ 10 - 250 G).