Coherent control and angular momentum transfer in semiconductor and plasmonic nanostructures

Semiconductor and plasmonic nanostructures have attracted considerable attention during the last decade. Semiconductors are the basis of today's information technology because of the possibility of tailoring electrical and optical properties on a detailed level. An elementary optical excitation in semiconductors is the electron-hole pair (exciton) with large oscillator strength which potentially enables ultrafast information processing. However, for quantum information applications excitons have been scarcely considered because of their limited optical coherence time due to complex many body interactions and their short radiative lifetime (below 1 ns) being the downside of the large oscillator strength. In nanostructures such as quantum dots (QDs) the optical decoherence is weak but still limited by radiative decay. Therefore approaches to involve the long-lasting coherence of resident electron spins have been pursued recently. The key excitation in plasmonics is the surface plasmon polariton (SPP), which is a coupled oscillation of the electromagnetic field and electron plasma in a metal. SPPs allow electromagnetic energy to be concentrated in nanoscale volumes at the interface between a metal and a dielectric, leading to an enhancement of linear and nonlinear optical effects. Current state of the art in nanotechnology allows fabrication of sophisticated metallic structures thus making possible light engineering at the nanoscale. Plasmonic structures may be shaped to manipulate the polarization of the light into novel “orbital” angular momentum states. Therefore, placing semiconductor nanostructures in the vicinity of plasmonic structures may establish transfer of angular momentum to a QD spin as well as efficient coherent control of electronic states. In order to achieve these goals detailed knowledge of near-field distribution of the electromagnetic fields and their propagation, optical response of the system under excitation with optical pulses which is governed by dynamics of electronic states in each of the constituents (semiconductor and plasmonic nanostructures) and combined hybrid structures are required.