Research objectives and content
The investigation of the optical properties and the nonequilibrium carrier dynamics in semiconducto} nanostructures is of great interest from both a fundamental physics as well as a device application point of view. To a great extent the carrier dynamics determine the performance of novel optoelectronic devices, such as quantum dot and quantum wire lasers which are expected to be significantly improved when reducing the dimensions from quantum well (2D) via quantum wire (lD) to quantum dot (OD) structures. Here, near-field scanning optical microscopy, providing a subwavelength spatial resolution of down to 50 nm, presents a particularly promising tool for studying single nanostructures and giving new insight into the physics of these structures. In this project it is planned to develop and demonstrate the potential of near-field reflection spectroscopy for the characterization of the nanoscopic optical properties of semiconductor nanostructures. The technique will be combined with femtosecond pump-probe techniques for studying processes such as the trapping of carriers into the wire and the nonequilibrium dynamics of carriers within the wire. The use of ultrafast, luminescence-based detection schemes, such as luminescence up-conversion, was unsuccessful, due to the low light levels in the near-field experiments available with present-day near-field fiber probes . It is therefore intend, during this project to develop near-field reflection spectroscopy as a new tool for the optical characterization of semiconductor nanostructures. In the moment, the MBI facility is unique in Europe in combining both low-temperature near-field spectroscopy of semiconductor nanostructures and ultrafast time-resolved detection schemes. The laboratory thus seems to be an ideal choice for performing the proposed experiments and a training period in this group will give to me the chanche to develope this thechnique in Italy, where at me moment it et ist a vey large intetest in developmg mis mecnique.