Which is also a method to shift light pulses by the shortest of durations! Insert an optical delay line into the setup and by varying the path length, you can d

Which is also a method to shift light pulses by the shortest of durations! Insert an optical delay line into the setup and by varying the path length, you can delay a light pulse by a tiny amount of time, e.g. for a pump-probe experiment (a pump-probe experiment works like this: first pulse does something to the system ("pump"), second pulse comes a short time later and reads out ("probes") the state of the system at that time. Changing the time delay gives an idea of the dynamics). Here is a drawing of an optical delay line: https://www.thorlabs.com/images/TabImages/Delay_Line_Kit_D1-780.gif https://www.thorlabs.com/images/TabImages/Delay_Line_Kit_D1-... The part labelled "V-Block" can move along the "translation stage" which changes the length of the optical path by twice this amount. Use the speed of light to calculate which delay the pulse incurred over the distance. You can now send pulse after pulse through your setup while changing the delay by tiny amounts to see how things (e.g. chemical processes) happen on these time scales.