Excitonic Structures and Optical Properties of Quantum Dots

Abstract

The spatial confinement of electrons and holes along all three dimensions leads to a discrete energy level structure with sharp optical absorption lines. In this sense a semiconductor quantum dot (QD) can be regarded as an artificial solid-state atom. The concentration of the oscillator strength to sharp exciton transitions makes QDs very attractive for electro-optic and nonlinear optical applications. To be more specific, QDs are considered as promising elements for implementing the coherent control of the quantum state, which is an essential function to achieve quantum information processing and quantum computation [1]. Recently, very fine structures were observed in exciton photoluminescence (PL) from GaAs quantum wells (QWs) [2–4]. These sharp lines are interpreted as luminescence from localized excitons at island structures in the QW. These island structures can be regarded as zero-dimensional QDs. The excitonic wave function has been manipulated by controlling the optical phase of the pulse sequence through timing and polarization [5]. In this wave function manipulation, important features are the sharp spectral lines, which indicate a long coherence time, and well-defined polarization characteristics. In view of this recent progress, in this section we discuss the fundamental physics of QDs, focusing on their excitonic optical properties.