Bandwidth limited pulse
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A bandwidth limited pulse is a pulse of a wave that has the minimum possible duration for a given spectral bandwidth. Optical pulses of this type can be generated by modelocked lasers. Bandwidth limited pulses have a constant phase across all frequencies making up the pulse.
Any waveform can be disassembled into its spectral components by Fourier analysis or Fourier transformation. The length of a pulse thereby is determined by its spectral components. Though knowledge of the spectral components is not enough to determine the pulse shape. The relative position (spectral phase) of the spectral components has to be known as well.
A bandwidth limited pulse can only be kept together if the dispersion of the medium the wave is travelling through is zero, otherwise dispersion management is needed to revert the effects of unwanted dispersion changes.
Keeping pulses bandwidth limited is necessary to compress information in time or to achieve high field densities, as with ultrashort pulses in modelocked lasers.