Eur. Phys. J. D 31, 107-112 (2004)
https://doi.org/10.1140/epjd/e2004-00123-2

Fluorescence from doubly driven four-level atoms

A density matrix approach

Raman Research Institute, Sadashivnagar, Bangalore 560 080, India

Corresponding author: ^a andal@rri.res.in

Received: 14 May 2004
Revised: 2 July 2004
Published online: 21 September 2004

Abstract

The unusually narrow features in the fluorescence from ⁸⁵Rb driven by two laser fields L1 and L2, reported in [1], are explained on the basis of a four-level density matrix calculation. The L2 laser enables atom transfer to the fluorescing levels connected by the strong L1 laser. In turn the L1 laser causes the Autler-Townes splitting of the upper levels connected by L2 laser. These two effects are shown to maximise fluorescence within a narrow spectral range of the scanned L2 laser due to velocity selection of atoms from co-propagating and counter propagating L1 and L2 lasers. The analysis reveals the existence of narrow spectral features from a collection of atoms at room temperature even in the absence of induced coherences between the levels.