Limits in preparation of coherent population trapping states

Wolfgang Maichen, Rainer Gaggl, Eugeny Korsunsky +1 more

Ferruccio Renzoni, E. Arimondo

The role of the depopulation and repopulation pumping mechanisms in coherent population trapping (CPT) is discussed. The case of open F g → F e transitions resonant with polarized laser light of different polarizations is examined. The efficiency of the preparation of the atomic population into the dark state is studied both for exact Raman resonance and for small Raman detuning. Dependences of the CPT-preparation on the laser polarization are described.

Wolfgang Maichen, Rainer Gaggl, Eugeny Korsunsky +1 more

Jingzhong Guo, Eugeny Korsunsky, E. Arimondo

One-dimensional velocity-selective coherent population trapping (VSCPT) in a cascade atomic configuration, with the second excited level a Rydberg state, is investigated through numerical calculations. The trapping efficiency for the case of travelling wave lasers is derived from the solution of the optical Bloch equations. For excitation by bichromatic standing waves, the energy-band approach is applied. Although the cooling process is limited by the spontaneous emission decay of the Rydberg state, the coexistence of polarization-gradient cooling and VSCPT in the case of standing waves allows the preparation of the majority of the atomic population in a cold Rydberg state.

Alexander R. Onur, J. P. de Jong, Danny G. O’Shea +3 more

We experimentally demonstrate how coherent population trapping (CPT) for donor-bound electron spins in GaAs results in autonomous feedback that prepares stabilized states for the spin polarization of nuclei around the electrons. CPT was realized by excitation with two lasers to a bound-exciton state. Transmission studies of the spectral CPT feature on an ensemble of electrons directly reveal the statistical distribution of prepared nuclear-spin states. Tuning the laser driving from blue to red detuned drives a transition from one to two stable states. Our results have importance for ongoing research on schemes for dynamic nuclear-spin polarization, the central spin problem, and control of spin coherence.