Rong Yu

Propagation of a voltage-controlled infrared laser pulse and electro-optic switch in a coupled quantum-dot nanostructure

We study infrared-light propagation and dynamical control of a tunable three-level system in a driven quantum-dot (QD) molecule by means of interdot tunnelling instead of a pumping laser. By numerically solving coupled Bloch?Maxwell equations, it is shown that under the resonant tunnelling condition, an interband (IB) infrared-light pulse acting as a signal can propagate with transparency due to the strong tunnelling-induced coupling. However, when the applied bias voltage tilts the energy levels of the structure such that the levels of the different dots move out of resonance (i.e., the nonresonant tunnelling), with an increase of detuning ?12, the coupling efficiency of interdot tunnelling decreases considerably and the IB infrared-light pulse will be almost completely absorbed after a characteristic propagation length. This can work as an absorptive optical switch where a signal (IB infrared light) is fully controlled by the external bias voltage. Our calculations provide a guideline for the development of new types of nanoelectronic devices in the QD solid-state system, which is much more practical than that in an atomic system because of its flexible design and the controllable (tunable) interference strength.

Propagation of twin light pulses under magneto-optical switching operations in a four-level inverted-Y atomic medium

Propagation dynamics of twin laser pulses through a cold four-level inverted-Y atomic medium is investigated theoretically via switching on and off an external magnetic field under the application of a strong driving field. By numerically solving the coupled Bloch–Maxwell equations for atom and field simultaneously on a spacetime grid, our spatio-temporal results clearly show that dynamic control of twin-pulse propagation and magneto-optic dual switching operation are possible in such an inverted-Y system. The proposed scheme may be used for the design of magneto-optic switching and magneto-optic storage devices.