Femtosecond Laser Pulses and Pulse Shaping

The experiments in this thesis have been performed using femtosecond laser pulses at different wavelengths. The second and third harmonic of of the fundamental output (800 nm) of a commercial laser have been used in several experiments. In other experiments laser pulses in the visible were required. A homebuilt non-collinear optical parametric amplifier (NOPA) has been used to generate tunable femtosecond pulses in the visible range. To access the UV region (320-340 nm), the NOPA output and the fundamental laser output are mixed inside a α-Beta Barium Borate (BBO) crystal in a sum-frequency generation (SFG) process. A short description of the laser system and all these non-linear processes will be given in the first part of this chapter. Femtosecond laser pulses have an amplitude, phase and polarization. These parameters can be altered using a homebuilt pulse shaper. Pulse shaping will be discussed in detail in the second part of this chapter.