Control of spontaneous emission of quantum dots using correlated effects of metal oxides and dielectric materials.

We study the emission dynamics of semiconductor quantum dots in the presence of the correlated impact of metal oxides and dielectric materials. For this we used layered material structures consisting of a base substrate, a dielectric layer, and an ultrathin layer of a metal oxide. After depositing colloidal CdSe/ZnS quantum dots on the top of the metal oxide, we used spectral and time-resolved techniques to show that, depending on the type and thickness of the dielectric material, the metal oxide can characteristically change the interplay between intrinsic excitons, defect states, and the environment, offering new material properties. Our results show that aluminum oxide, in particular, can strongly change the impact of amorphous silicon on the emission dynamics of quantum dots by balancing the intrinsic near band emission and fast trapping of carriers. In such a system the silicon/aluminum oxide charge barrier can lead to large variation of the radiative lifetime of quantum dots and control of the photo-ejection rate of electrons in quantum dots. The results provide unique techniques to investigate and modify physical properties of dielectrics and manage optical and electrical properties of quantum dots.

Undamped ultrafast pulsation of plasmonic fields via coherent exciton-plasmon coupling.

We show that under certain conditions the plasmonic field of a hybrid system consisting of a metallic nanoparticle and a semiconductor quantum dot can be converted into ultrashort stationary pulses with temporal widths as short as 300 ps. This happens as this system interacts with an infrared and visible laser fields, both with time-independent amplitudes. These fields generate quantum coherence via simultaneous interband and intersubband transitions of the quantum dot, forcing the polarization dephasing rate of the quantum dot to become negative during the plasmon pulses. This makes the amplitudes of such pulses time-independent (undamped), indicating total suppression of quantum decoherence of the quantum dot. These results suggest that hybrid quantum dot-metallic nanoparticle systems can act as undamped coherent-plasmonic oscillators.