Editing Ultrafast monochromator (section)

An '''ultrafast monochromator''' is a [[monochromator]] that preserves the duration of an [[ultrashort pulse]] (in the [[femtosecond]], or lower, time-scale).<ref name="PolettoFrassetto2012">{{cite journal|last1=Poletto|first1=Luca|last2=Frassetto|first2=Fabio|last3=Villoresi|first3=Paolo|title=Ultrafast Grating Instruments in the Extreme Ultraviolet|journal=IEEE Journal of Selected Topics in Quantum Electronics|volume=18|issue=1|year=2012|pages=467–478|issn=1077-260X|doi=10.1109/JSTQE.2011.2135338|s2cid=26107534 }}</ref><ref name="TschentscherPatthey2017">{{cite journal|last1=Tschentscher|first1=Thomas|last2=Patthey|first2=Luc|last3=Brenner|first3=Günter|last4=Frassetto|first4=Fabio|last5=Kuhlmann|first5=Marion|last6=Ploenjes|first6=Elke|last7=Poletto|first7=Luca|editor-first1=Thomas |editor-first2=Luc |editor-last1=Tschentscher |editor-last2=Patthey |title=Grating monochromator with ultrafast response for FLASH2 at DESY
|volume=10237|year=2017|pages=1023716|issn=0277-786X|doi=10.1117/12.2264885|series=Advances in X-ray Free-Electron Lasers Instrumentation IV|s2cid=56251242 |url=http://bib-pubdb1.desy.de/record/396797/files/1023716.pdf}}</ref>  Monochromators are devices that select for a particular wavelength, typically using a [[diffraction grating]] to [[dispersion (optics)|disperse]] the light and a slit to select the desired wavelength; however, a diffraction grating introduces path delays that measurably lengthen the duration of an ultrashort pulse.   An ultrafast monochromator uses a second diffraction grating to compensate time delays introduced to the pulse by the first grating and other dispersive optical elements.