Experimental advances in the optical spectroscopy of carrier spin noise

The digital revolution is based on the miniaturization of semiconductor-based transistors. This allowed for a rapid acceleration of data processing speed during the last decades. In the future there will be a demand for even faster and more effective processing than it is known today. On the other hand, however, miniaturization cannot be driven far beyond the current level. This is because quantum effects will inevitably come into play. Being aware of these challenges, scientists are currently trying to develop novel technologies that incorporate quantum effects to revolutionize information processing on some day. One promising branch - the so-called spintronics - aims at the full control over the spin state of the charge carrier, i.e. the electron or hole. It is clear that such artificial manipulation of the spin state puts the spin into a nonequilibrium state from which it relaxes back to the equilibrium state because of interaction with the environment. Hence, spintronics faces two challenges: first, the creation of environments where long-lived nonequilibrium spin states can be created; second, the development of techniques that allow to reliably measure the relaxation dynamics. In regard of the latter, the optical spectroscopy of the carrier spin noise, i.e. the statistical spin fluctuations in thermal equilibrium, represent a novel and promising way to obtain spin dynamics: one finds that the power spectrum of the spin noise is equivalent to the Fourier transform of the nonequilibrium relaxation dynamics of the spin. This work provides an overview on recent experimental achievements in the carrier spin noise spectroscopy of atomic gases, bulk semiconductors and semiconductor nanostructures.