Comment Re:How do they measure this? (Score 1) 76
The basic technique involves splitting the pulse into two, sending each pulse down different paths, recombining them in such a way that a third pulse is generated whose strength is proportional to the overlap between the first two pulses. By varying the relative delay between the two pulse replicas, you change the final intensity, and you have mapped the spatial delay onto time delay and effectively measured the pulse. For such short pulses, there are some special tricks that are needed, and a bit of computer reconstruction, but that is the basic physical idea.
