Editing Ultrashort pulse (section)

==Measurement techniques==
Several techniques are available to measure ultrashort optical pulses.

Intensity [[optical autocorrelation|autocorrelation]] gives the pulse width when a particular pulse shape is assumed.

[[Spectral interferometry]] (SI) is a linear technique that can be used when a pre-characterized reference pulse is available. It gives the intensity and phase. The algorithm that extracts the intensity and phase from the SI signal is direct. [[Spectral phase interferometry for direct electric-field reconstruction]] (SPIDER) is a nonlinear self-referencing technique based on spectral shearing interferometry. The method is similar to SI, except that the reference pulse is a spectrally shifted replica of itself, allowing one to obtain the spectral intensity and phase of the probe pulse via a direct [[Fast Fourier transform|FFT]] filtering routine similar to SI, but which requires integration of the phase extracted from the interferogram to obtain the probe pulse phase.

[[Frequency-resolved optical gating]] (FROG) is a nonlinear technique that yields the intensity and phase of a pulse. It is a spectrally resolved autocorrelation. The algorithm that extracts the intensity and phase from a FROG trace is iterative. Grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields ([[GRENOUILLE]]) is a simplified version of FROG. (''Grenouille'' is French for "[[frog]]".)

Chirp scan is a technique similar to [[MIIPS]] which measures the spectral phase of a pulse by applying a ramp of quadratic spectral phases and measuring second harmonic spectra. With respect to MIIPS, which requires many iterations to measure the spectral phase, only two chirp scans are needed to retrieve both the amplitude and the phase of the pulse.<ref name="LoriotGitzinger2013">{{cite journal|last1=Loriot|first1=Vincent|last2=Gitzinger|first2=Gregory|last3=Forget|first3=Nicolas|title=Self-referenced characterization of femtosecond laser pulses by chirp scan|journal=Optics Express|volume=21|issue=21|year=2013|pages=24879–93|issn=1094-4087|doi=10.1364/OE.21.024879|pmid=24150331|bibcode = 2013OExpr..2124879L |doi-access=free}}</ref>

[[Multiphoton intrapulse interference phase scan]] (MIIPS) is a method to characterize and manipulate the ultrashort pulse.