We consider the effects of the time-dependence of the frequency of a probe field in a three-level system when the probe field is scanned in frequency. We find that, under conditions of weak coupling and probe fields, the resonance can show ringing when the scan rate is greater than the ground state recovery time.
Near the condition of electromagnetically induced transparency in a three-level system, the absorption experienced by the weak probe laser beam interacting with one transition is very sensitive to the frequency detuning of the strong-coupling laser beam coupled to another transition. When the frequency detuning of the coupling laser is modulated at different frequencies, the resulting change in probe absorption as a function of that modulation frequency can be described by a transfer function. The effects on the transfer function from various experimental parameters are calculated numerically. Experimental measurements are shown to be in good agreement with the predicted behavior.
We present a theoretical study on the frequency position and the linetype of Electromagnetically Induced Transparency (EIT) in a four-level atomic system with a coupling field, two microwave fields and a probe field. The absorption spectrum which is characterized by two EIT windows is obtained by a weak probe field scanning corresponding transition. It can be found that the frequency position and the linetype of EIT change with the relative phase of the two microwave fields. The frequnecy interval reaches the minimum when the relative phase is reverse. If two microwave fields have the same strength and reverse phase, the absorption spectrum will exhibit an EIT. This proposes a way to controlling frequency position of EIT by modulating the relative phase between two fields.
Electromagnetically induced transparency (EIT) resonance in a $\ensuremath{\Lambda}$ configuration is obtained when the frequencies of two fields are close to resonance with two of the transitions and their frequency difference matches the frequency of the third transition. In this situation the spectrum of one swept field as a probe gives a simple transparency feature. However, when an additional field drives the third transition the EIT feature associated with the probe is split. This perturbed EIT is illustrated for both single and bichromatic driving fields. In the single-driving-field case a density matrix treatment is shown to be in reasonable agreement with experiment, and in both single and bichromatic cases the structure in the spectrum can be explained using the dressed-state formalism. The dressed states can also be used to account for subharmonic resonances observed in the strong-probe regime.
The simplest three-level system exhibiting electromagnetically induced transparency (EIT) exhibits an effective conjugation symmetry as well as a transposition symmetry. Breaking the conjugation symmetry leads to a distinct chirp asymmetry, i.e., the differential response to a frequency increase versus a frequency decrease. The dynamic range of the many tunable optical parameters of the Hanle–Zeeman EIT resonance makes it an ideal platform for testing the chirp asymmetry’s dependence on the CP-breaking parameter and broadening. We describe the theory and compare it to an experiment using 87 Rb in a buffer gas cell. In contrast with earlier multi-photon chirp asymmetry work, this present effort explores the asymmetry at nearly one-billionth the earlier chirp rate and fully explores its universal features. The chirp asymmetry may have metrological consequences for understanding systematic dependence on modulation/demodulation parameters.