Abstract
Since discrete multilevel transitions of quantum-dot molecules driven by external electromagnetic fields can exhibit quantum coherence effects, such an optical characteristic can be utilized to control propagation of electromagnetic wave through a quantum-dot molecule dielectric film. Since inner-dot tunneling in quantum-dot molecules can be controlled by a gate voltage, destructive quantum coherence among multilevel transitions in quantum-dot molecule would give rise to EIT (electromagnetically induced transparency). In this report, we shall investigate controllable on- and off-resonance tunneling effects of an incident electromagnetic wave through such a quan-tum-dot-molecule dielectric film, of which the optical response is tuned by the switchable gate voltage. We have found from the theoretical mechanism that a high gate voltage can cause the EIT phenomenon of quan-tum-dot-molecule systems, and under the condition of on-resonance light tunneling through the thin film, the probe field will propagation without loss if the probe frequency detuning is zero. By taking advantage of these effects sensitive to the tunable gate voltage, such quantum coherence would be inte-grated in certain photonic structures, and some devices such as photonic switching and transistors can be designed. Transient evolution of optical characteristics in the quantum-dot-molecule dielectric film (once the tunable gate voltage is turned on or off) is also considered in this report.
Highlights
Light propagation control is one of the key technologies with the development of photonic and optical science
We have found from the theoretical mechanism that a high gate voltage can cause the EIT phenomenon of quantum-dot-molecule systems, and under the condition of on-resonance light tunneling through the thin film, the probe field will propagation without loss if the probe frequency detuning is zero
Quantum coherence, which occurs in alkali-metal atomic vapor and semiconductor quantum-dot media, has been studied in the literature [1]-[12]
Summary
Light propagation control is one of the key technologies with the development of photonic and optical science. Since the gate voltage is zero, there exhibits no EIT effect at the probe resonance frequency ( δ = 0 ) In this case, both the reflectance R and the transmittance T are reduced by the two-level resonant absorption (caused by the 0 - 1 transition). Since there are some tunable parameters, e.g., the gate-voltage Rabi frequency and gate-voltage angular frequency, the optical response of quantum-dot molecular systems can be modified by external control fields (e.g., gate voltage), and the tunable reflection and transmission characteristics of the quantum-dot molecular film in the states of on- and off-resonance light tunneling can, be utilized to design some devices such as photonic switching and transistors. When the incident probe frequency detuning εδ = δ = ωp − ω10 =0 and the gate voltage Te = 3.0 meV, the EIT effect can occur, and the transmittance T increases and the reflectance R decreases. This, means that the transmission and reflection spectrum of an incident electromagnetic field (probe field) can be tuned via the gate voltage that is applied on the quantum-dot molecular thin film
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