Frontiers in ultrashort pulse generation: Pushing the limits in linear andnonlinear optics

Optical pulses in the 5-femtosecond range are produced by a variety of meth ods. Although different in technical detail, each method relies on the same three key components: spectral broadening due to the nonlinear optical Ker r effect, dispersion control, and ultrabroadband amplification. The state o f the art of ultrashort pulse generation is reviewed with a focus on direct laser oscillator schemes.