Optical Studies of Single Quantum Dots
Abstract
Atomic physics progressed rapidly at the beginning of the last century, thanks, in large part, to optical spectroscopy. Quantization and spin were discovered through optical studies, as were other fundamental atomic properties. With the advent of the laser, physicists learned how to manipulate atomic wavefunctions by applying coherent optical fields. More discoveries followed. Now, at the beginning of the new century, optical techniques are being used to explore a new scientific frontier: the atomlike entities known as quantum dots (QDs). Measuring 1-100 nm across, QDs are semiconductor structures in which the electron wavefunction is confined in all three dimensions by the potential energy barriers that form the QD's boundaries. A QD's electronic response, like that of a single atom, is manifest in its discrete energy spectrum, which appears when electron-hole pairs are excited. Although the wavefunction of a QD electron, and its corresponding hole, extends over many thousands of lattice atoms, the pair--termed an exciton--behaves in a quantized and coherent fashion. The coherence is relatively easy to detect and control optically--for two reasons. First, the superposition of the ground and excited states dephases more slowly in QDs than in higher-dimensional semiconductor structures. Second, QDs have large dipole moments (50-100 times larger than those of atoms). Thanks to these advantages, it is possible to probe and manipulate the wavefunction of a single QD.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2002
- Accession Number
- ADA447752
Entities
People
- Daniel Gammon
- Duncan G. Steel
Organizations
- United States Naval Research Laboratory