The standard output coupler uses a partially reflecting mirror as explained in chapter 3.3. The part of the beam which is not reflected back into the active medium, is transmitted out.
In a continuous wave laser (in which the radiation is emitted continuously), most of the radiation is reflected back into the cavity, and only a few percent is transmitted out.
In certain pulsed lasers most of the radiation within the cavity at
a specific moment is transmitted out in a pulse (see