Abstract
We report a new experimental approach where an order of magnitude enhancement of the electromagnetically induced absorption (EIA) resonance contrast, thus making it similar to that of the EIT resonance contrast is observed under the same conditions. The EIA signal results from the interaction of a weak probe beam with a ground state that has been driven by the pump (counter-propagating) beam. Probe absorption spectra are presented where the laser frequency is slowly detuned over the D1 line of 39K vapor contained in a cell with a PDMS antirelaxation coating. In addition to the frequency detuning, a magnetic field orthogonal to the laser beams is scanned around zero value at a higher rate. With both laser beams linearly polarized, an EIT resonance is observed. However, changing the pump beam polarization from linear to circular reverses the resonance signal from EIT to EIA.
Highlights
The phenomenon of electromagnetically induced transparency (EIT) has many applications in laser physics, precision laser spectroscopy, quantum information, all-optical magnetometers, miniaturized atomic clocks, precision measurements of fundamental symmetry, etc
It is worth noting that the population of the ground-state magnetic sublevels not interacting with the pump beam is the highest in the case of magnetic field B = 0, i.e. at the maximum of the Hanle electromagnetically induced absorption (EIA) resonance profile that is measured by the lower intensity probe beam
With the enhancement of the magnetic field value B in both directions with respect to B = 0, the atoms accumulated on m = 1,2 ground Zeeman sublevels evolve on the other Zeeman sublevels and the probe beam sees a reduction of atomic population, i.e. the low-absorption wings of the EIA profile
Summary
The phenomenon of electromagnetically induced transparency (EIT) has many applications in laser physics, precision laser spectroscopy, quantum information, all-optical magnetometers, miniaturized atomic clocks, precision measurements of fundamental symmetry, etc. In the fluorescence signal from a vapor cell, the EIT resonance is usually observed as a narrow dip. One of the most significant and useful features of the EIT resonance is its width, which can be much smaller than the natural line width. Perhaps these resonances are the narrowest ones that can be observed in a cell filled with ‘hot’ atomic vapor (i.e. at room temperature). The electromagnetically induced absorption (EIA) resonance, a sub-natural-width resonance (“bright resonance”), has applications in an enhancement of the group velocity of the light (“fast” light), four-wave mixing, magnetic field mapping of cold atomic samples.
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