Abstract
Electromagnetically induced transparency (EIT) is an optical phenomenon which allows a drastic modification of the optical properties of an atomic system by applying a control field. It has been largely studied in the last decades and nowadays we can find a huge number of experimental and theoretical related studies. Recently a similar phenomenon was also shown in quantum dot molecules (QDM), where the control field is replaced by the tunneling rate between quantum dots. Our results show that in the EIT regime, the optical properties of QDM and the atomic system are identical. However, here we show that in the strong probe field regime, i.e., “coherent population trapping” (CPT) regime, it appears a strong discrepancy on the optical properties of both systems. We show that the origin of such difference relies on the different decay rates of the excited state of the two systems, implying in a strong difference on their higher order nonlinear susceptibilities. Finally, we investigate the optical response of atom/QDM strongly coupled to a cavity mode. In particular, the QDM-cavity system has the advantage of allowing a better narrowing of the width of the dark state resonance in the CPT regime when compared with atom-cavity system.
Highlights
It is well known that quantum interference between different excitation paths can modify the optical response of a system, giving rise for example to the suppression of absorption of the incident light when the interference between these channels is destructive
We show that the crucial parameter which allows for the enhancement of the nonlinear effects in Electromagnetically induced transparency (EIT)/coherent population trapping” (CPT) processes is the asymmetric decay rate of the excited state
We have investigated the influence of the asymmetric decay of the excited state of three-level systems in
Summary
For small values of the control field Rabi frequency or Tunnelling rate (Θ → 0), the non null Γ32 leads the population of the system to the ground state |2〉, which is not coupled to the cavity mode, increasing the transmission (empty cavity situation) This is equivalent to an effective decay from level |1〉 to |2〉 – see inset of panel (c), where we have included the effective decay in the QDM-cavity dynamics. As we see, when we decrease ΩC (Te), i.e., in the CPT regime, the transmission around ΔP = 0 increases for the atomic system while for the QDM system it remains non-null only exactly on the dark state resonance, i.e., at ΔP = 0 This happens because the population of the ground state |2〉 increases due to the presence of the decay channel associated to Γ32 as ΩC → 0, making the atom-cavity system transparent to the probe field (empty cavity situation). For stronger values of g the minimum FWHM for atomic and QDM systems becomes closer
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