Lets say we have a laser beam with finite temporal coherence. A broadband spectrum with a transform limited pulse of 100fs.

If we measure its temporal coherence when the pulse is transform limited and if we measure a chirped pulse that is let say 1ps would the temporal coherence change.

Just trying to understand temporal coherence relation to pulse length and dispersion qualitatively.

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    $\begingroup$ Please let us know what you mean by "fs order", GDD, and TOD. $\endgroup$
    – garyp
    Commented Mar 9, 2015 at 20:41
  • $\begingroup$ Edits of old posts that are already resolved bump those threads to the front page; they're OK so long as it's not a flood of unactionable old threads there. Six posts in fifteen minutes is on the boundary of becoming rather too much. $\endgroup$ Commented Nov 6, 2017 at 17:06

1 Answer 1


Technically, the coherence time will remain the same. This will be determined by the width of each frequency component in the pulse, which does not depend on the phase relationship.

Another way of thinking about it is that coherence time = coherence length / phase velocity. Consider free space, where group velocity = phase velocity. The coherence length is the maximum distance at which the pulse still looks like its original self, and the coherence time just becomes the time the pulse takes to get to that distance.


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