Low- and high-intensity velocity selective coherent population trapping in a two-level system

Abstract

Abstract. -An experimental investigation is made of sub-recoil cooling by velocity selective coherent population trapping in a two-level system in Sr. The experiment is carried out using the narrow linewidth intercombination line at 689 nm. Here, the ratio between the recoil shift and the linewidth is as high as 0.64. We show that, on top of a broader momentum profile, subrecoil features develop, whose amplitude is strongly dependent on the detuning from resonance. We attribute this structure to a velocity selective coherent population trapping mechanism. We also show that the population trapping phenomenon leads to complex momentum profiles in the case of highly saturated transitions, displaying a multitude of subrecoil features at integer multiples of the recoil momentum.

Homodyne detection of a two-photon resonance assisted by cooperative emission

“…Since the first experimental evidence of coherent population trapping (CPT) [1] and electromagnetically induced transparency (EIT) [2], the narrow dark two-photon resonance [3] has been a key feature for many fundamental and practical phenomena. Without being exhaustive, these include slowing and storage of light [4,5], quantum memories [6,7], CPT clocks [8][9][10][11][12][13], microwave and terahertz generation and detection [14][15][16][17], laser cooling [18,19], Raman velocimetry [20], and many-body photonics systems [21][22][23][24]. A generalization of CPT, involving dark multiphoton resonances, has also been demonstrated recently [25].…”