Abstract
The saturated absorption technique is an elegant method widely used in atomic and molecular physics for high-resolution spectroscopy, laser frequency standards and metrology purposes. We have recently discovered that a saturated absorption scheme with a dual-frequency laser can lead to a significant sign reversal of the usual Doppler-free dip, yielding a deep enhanced-absorption spike. In this paper, we report detailed experimental investigations of this phenomenon, together with a full in-depth theoretical description. It is shown that several physical effects can support or oppose the formation of the high-contrast central spike in the absorption profile. The physical conditions for which all these effects act constructively and result in very bright Doppler-free resonances are revealed. Apart from their theoretical interest, results obtained in this manuscript are of great interest for laser spectroscopy and laser frequency stabilization purposes, with applications in laser cooling, matter-wave sensors, atomic clocks or quantum optics.
Highlights
25 July 2017The saturated absorption technique is an elegant method widely used in atomic and molecular physics for high-resolution spectroscopy, laser frequency standards and metrology purposes
In recent decades, outstanding progress in laser science and technology has allowed exciting atomic physics experiments to be performed by resolving features in atomic and molecular spectra [1] with unprecedented resolution and accuracy [2]
A residual inhomogeneity of the magnetic field in the cell could affect the widths of these resonances differently. These experiences demonstrate clearly that at null magnetic field: (i) hyperfine splitting (HFS)-coherent population trapping (CPT) states are present at null Raman detuning, (ii) the CPT amplitude is reduced but non-null at optical resonance d = 0 in crossed polarizations, (iii) the CPT amplitude is higher for non-null optical detuning, (iv) HFS-CPT effects can contribute to the observation of the Doppler-free reversed dip in the dual-frequency regime
Summary
The saturated absorption technique is an elegant method widely used in atomic and molecular physics for high-resolution spectroscopy, laser frequency standards and metrology purposes. The physical conditions for which all these effects act constructively and result in very bright Doppler-free resonances are revealed. Apart from their theoretical interest, results obtained in this manuscript are of great interest for laser spectroscopy and laser frequency stabilization purposes, with applications in laser cooling, matterwave sensors, atomic clocks or quantum optics
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