Critical repair of an ultrafast laser system for research on semiconductor materials

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In semiconductor electronics and photonics, the response of electrons to light is what underpins their function. For example, in solar cells, absorption of light produces charges that result in electrical current and thus produce electrical energy. In optical devices, light is manipulated by the active medium when it interacts strongly with electrons in the semiconductor. In our research group, we study in great detail the interactions between light and electrons in semiconductors, particularly in so-called organic semiconductors, in which molecular motifs are the building blocks of solid-state architectures instead of atoms as in traditional semiconductors. In order to study the fastest electronic processes in real time, we use very short laser pulses (as short as 10 fs, that is 10 billionth of a millionth of a second) derived from a laser system producing one such short pulse every millisecond interval. The resulting train of laser pulses then interacts with the sample of interest, and its response is then probed as a function of time following that event. For example, the intensity of light re-emitted by the sample is analyzed as a function of time. These measurements unravel a wealth of information on the basic optical properties of the material, which is essential to underpin their function in a plethora of applications in optoelectronics and photonics.