Tunable and polarization-controlled high-contrast bright and dark coherent resonances in potassium

Abstract

We demonstrate high-contrast Electromagnetically Induced Absorption (EIA) bright resonances on the D 1 line of 39 K with characteristics comparable to those of the Electromagnetically Induced Transparency (EIT) dark resonances observed in the same conditions. EIA is produced by the interaction of a weak probe beam with the atomic ground state driven in a degenerate coherent superposition by either a co-or counterpropagating pump beam. We have obtained an order of magnitude increase of the EIA's contrast with respect to previous similar experiments, performed with other alkalis, without compromising its linewidth. Furthermore, we show that the magneto-optic resonances can be continuously tuned from EIT to EIA by changing the relative handedness of circular polarizations of pump and probe beams, or depending on whether they co-or counter-propagate. This opens new perspectives in the use of EIA in a broad range of physical domains and in a large wealth of potential applications in optics and photonics. Contrary to Coherent Population Trapping and Electromagnetically Induced Transparency (EIT) with their ultra-narrow linewidths [1][2][3][4][5][6][7][8], Electromagnetically Induced Absorption (EIA) has found limited applications, mainly due to its broader linewidth and significantly smaller contrast. Nonetheless, an increasing interest in EIA was recently generated in view of potential applications, such as enhancement of the group velocity of light [9] and photonic metamaterials [10].EIA linewidths of several tens of kiloHertz have been reported, either with bichromatic excitation of Zeeman sublevels[11] or in Hanle configuration [12][13][14]. Bi-chromatic Hanle configuration has been explored by using Rb D 1 and D 2 lines [15]. Low-contrast EIA, resulting from EIT on D 2 line, was reported. Higher contrast EIA has been observed in [16], although overlapped to large background, which could be detrimental for highly-selective applications. More recently, sub-kHz EIA resonances were observed in Rb [17] and Cs [18,19]. In both cases, however, the contrast was of only a few percents. A pump/probe scheme in Hanle configuration for high-contrast EIA was proposed in a buffered vapor cell [20]. To date, however, no experimental demonstration has been reported. Highcontrast EIA has been observed on the 87 Rb D 2 line by using a complex excitation scheme with three separate photonic fields [21], and was theoretically investigated in [22]. EIA was also observed in the Paschen-Back regime in a purely non-degenerate three-level ladder system in 87 Rb [23]. Furthermore, while Rb and Cs have been widely investigated, this is the first observation of EIA in K, confirming our preliminary results [24].In this Letter, we report on an alternative and simpler approach for large contrast EIA in Hanle configuration using a pump/probe excitation scheme. We have observed EIA resonance contrast exceeding 50% in thermal K vapor. In this case, hyperfine optical pumping, which accumulates atoms to levels non interacting with the light [25,26], ...

High-quality electromagnetically-induced absorption resonances in a buffer-gas-filled vapour cell

“…Recently, interesting results were obtained in potassium atoms in a cell with antirelaxation coating of the walls [38]. The authors used an observation configuration consisting of two counter-propagating circularly polarized laser beams and a transverse magnetic field.…”

High-quality level-crossing resonances under counterpropagating circularly polarized light waves for applications in atomic magnetometry

“…2 in Ref. [26] for potassium vapors. The comparison reveals a much higher contrast and CWR in the case of Cs vapors.…”

“…It should be noted that similar configurations have already brought relevant results for developing atomic clocks [24,25]. The same light field geometry was studied in [26] in a cm-size K vapor cell with antirelaxation coating of the walls. In the present study we show that a buffer-gas-filled Cs vapor cell can provide much better contrast-to-width ratio (CWR) of the GSHE resonance due to the spectral resolution of ground-state hfs levels.…”

Electromagnetically induced absorption scheme for vapor-cell atomic clock

“…A relevant number of EIA-based schemes and experiments using single-frequency magnetooptical (Hanle-like) configurations or dual-frequency light-field configurations have been reported in the literature [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. It should be noted that in many of these works, the physical origin of the EIA effect differs from the process of spontaneous transfer of Zeeman coherences or populations identified in pioneering EIA studies [7,36].…”