Direct observations of coherent light matter interactions require that the coherent wave function of the material persists longer than the required measurement time. The decoherence time in room temperature semiconductors is 0.3-1 ps and therefore coherent experiments are normally performed at cryogenic temperatures. However, if the coherent interaction can be induced by a short pulse and measured by an ultra-fast technique, it is possible to observe such interactions at room temperature.

 The FROG and X-FROG schemes allow measuring the complex electric field envelope of a short pulse (amplitude and phase) on time scales of the pulse itself with practically unlimited temporal resolutions. This presentation describes direct measurements of coherent light matter interactions in electrically driven quantum dot and quantum dash optical amplifiers operating at room temperatures. Using the X-FROG technique we have observed several such interactions including: Rabi Oscillations, Self-Induced Transparency and Coherent Pulse Area Manipulation. A modified version of the system which uses two pulses offers also to observe directly the evolution of decoherence in a Ramsey-analogous experiment and to determine the decoherence time directly.

 The experiments are supported by a comprehensive FDTD model which solves the Maxwell- Schrödinger equations. The model takes into account the inhomegeneously broadened nature of the self-assembled nano structured gain medium. The inclusion of the gain inhomogeneity is necessary since the pulse spectrum is wider than the room temperature homogeneous linewidth and hence it excites an assembly of resonances (each behaving as an effective two level system). The overall response has cumulative contributions from all those excited resonances and hence the model needs to consider them.