The physics of attosecond light pulses

The word 'attosecond' (1 as = 10−18 s) officially entered the vocabulary of physics when sub-femtosecond pulses of UV/XUV light produced either by nonlinear frequency conversion of a ultra-short infrared pump pulse or Fourier synthesis of broad bandwidth radiation were established. The physics of these pulses is based on nonlinear, nonperturbative laser–atom interaction: stimulated Raman scattering or high harmonic generation (HHG) is used to generate the necessary bandwidth, which naturally encompasses the visible and UV/XUV spectral range. However, the crucial element for attosecond pulse generation is the control of the spectral phase. New methods of temporal characterization at frequencies lying in the…