Pulsed lasers are often used to study very short phenomena. It is therefore important that the laser pulse be synchronized with the phenomenon. This can be achieved in one of three ways, depending on the particular type of experiment :
1) The short phenomenon is first detected. Upon detection, a trigger signal is sent to the laser system, that will then emit a light pulse. This set up is used when there is a large uncertainty about the time of occurrence of the phenomenon.
2) To the contrary, the laser pulse may be emitted with a time uncertainty ("jitter") larger than the duration of the phenomenon itself. Upon exiting the cavity, the pulse is detected, and the signal used to trigger the phenomenon. It may be necessary to delay the laser pulse on an optical delay line.
3) If both the phenomenon and the laser have low jitters, both may be triggered by a common external signal.