Autocorrelators & FROG (Ultrafast lasers)
Optical Autocorrelators are used to measure pulse duration of ultra-short laser pulses. The principle is to create two copies of the laser beam of interest with a beam splitter. The copies are superimposed in a nonlinear medium (SHG crystal), where they interact generating a third beam. As the overlap of the two copies depends on the pulse duration, analyzing the third beam allows to calculate the pulse duration.