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. 1 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...
