6. Conclusion

In this article we have described the basic elements of the physical techniques for generating pulses delivered by laser sources on ever shorter time scales. We have progressively moved from millisecond (ms) pulses by a simple mechanical process, to nanosecond (ns) pulses by electro-optical triggering of a non-linear crystal constituting a Pockels cell or an acousto-optic modulator, then to the picosecond (ps) by mode-locking a laser cavity and, finally, to the femtosecond (fs) by the nonlinear Kerr effect, which plays on both spatial and temporal variations in laser beam intensity, known as self-focusing or Kerr lensing, and phase self-modulation. This presentation follows on logically from the articles on the fundamentals of solid-state lasers