Editing Ultrashort pulse (section)

==Pulse shape control==
Although optical devices also used for continuous light, like beam expanders and spatial filters, may be used for ultrashort pulses, several optical devices have been specifically designed for ultrashort pulses. One of them is the [[prism compressor|pulse compressor]],<ref>J. C. Diels, Femtosecond dye lasers, in ''Dye Laser Principles'', [[F. J. Duarte]] and L. W. Hillman (Eds.) (Academic, New York, 1990) Chapter 3.</ref> a device that can be used to control the spectral phase of ultrashort pulses. It is composed of a sequence of prisms, or gratings. When properly adjusted it can alter the spectral phase ''φ''(''ω'') of the input pulse so that the output pulse is a [[bandwidth-limited pulse]] with the shortest possible duration. A [[femtosecond pulse shaping|pulse shaper]] can be used to make more complicated alterations on both the phase and the amplitude of ultrashort pulses.

To accurately control the pulse, a full characterization of the pulse spectral phase is a must in order to get certain pulse spectral phase (such as [[bandwidth-limited pulse|transform-limited]]). Then, a [[spatial light modulator]] can be used in the 4f plane to control the pulse. [[Multiphoton intrapulse interference phase scan]] (MIIPS) is a technique based on this concept. Through the phase scan of the spatial light modulator, MIIPS can not only characterize but also manipulate the ultrashort pulse to get the needed pulse shape at target spot (such as [[bandwidth-limited pulse|transform-limited pulse]] for optimized peak power, and other specific pulse shapes). If the pulse shaper is fully calibrated, this technique allows controlling the spectral phase of ultrashort pulses using a simple optical setup with no moving parts. However the accuracy of MIIPS is somewhat limited with respect to other techniques, such as [[frequency-resolved optical gating]] (FROG).<ref name="CominRhodes2015">{{cite book|last1=Comin|first1=Alberto|last2=Rhodes|first2=Michelle|last3=Ciesielski|first3=Richard|last4=Trebino|first4=Rick|last5=Hartschuh|first5=Achim|title=Cleo: 2015|chapter=Pulse Characterization in Ultrafast Microscopy: a Comparison of FROG, MIIPS and G-MIIPS|year=2015|pages=SW1H.5|doi=10.1364/CLEO_SI.2015.SW1H.5|isbn=978-1-55752-968-8|s2cid=23655339}}</ref>