Role of tunneling induced coherence in modulation of absorption and dispersion in a quantum dot molecule with symmetrical coupling configuration

Abstract

Coherent control of optical effects are studied in a quantum dot molecule comprising triple quantum dots with the consideration of symmetric tunneling induced coupling. We have analyzed the origin of such coherence effects in terms of perturbative influence of the array of tunneling induced coherence terms associated with the semiclassical density matrix element relating to optically induced exciton generation. It has been shown that the coherence terms can significantly modify the absorptive and dispersive line shapes due to the change of condition of weak tunneling to moderate tunneling limited by the coherence dephasing effect. We have illustrated the evolution of Fano-like resonance controlling the absorptive line shapes under the conditions mentioned above. We have shown how, depending upon the variation of gate-biasing voltage, dispersion like features evolve in the absorptive case, while absorption-peak like features originate in case of dispersion. This is due to the appearance of non-linear Fano resonance inherent to this model. Our results highlight the appearance of a negative refractive index like pattern in the dispersive response of the line shape under such conditions.