Over the past two decades there have been tremendous advancements in the field of ultrafast laser technology which opened up new fascinating possibilities based on the unique properties of femtosecond light pulses. Properties, such as, the concentration of the energy in the pulse corresponding to only a few optical cycles, and the high peak powers which reach electric filed strength comparable to those of inner-atomic fields.

One area of physics the ultrafast laser technology had a tremendous impact is semiconductors physics and in particular the understanding of carrier dynamics in semiconductors. The driving force behind this movement other than the basic fundamental interest is the direct application of semiconductor devices and the endless need for faster response and faster processing of information. To improve and develop microelectronics devices and address these needs, the basic understanding of the various dynamical processes in the semiconductors has to be studied in detail. Therefore, the excitation of semiconductors out of their equilibrium and the subsequent relaxation processes with various rates has become a key area of semiconductor research. With the development of lasers that can generate pulses as short as a few femtoseconds the excitation and subsequent probing of semiconductors on an ultrashort timescale have become routine. Processes such as carrier momentum randomization, carrier thermalization and energy relaxation have been studied in detail using excite-and-probe novel techniques.