Term used to describe the area in which the working laser beam is created. Typically this includes the lasing medium, a pair of mirrors at either end of the cavity, and in some cases the Q-switch. This is the area where the cascading emission of photons happens and builds up energy. Many different designs of optical cavities are available which provide different performance characteristics.

(Resonator) Space between the laser mirrors where lasing action occurs.

a volume bounded by two or more reflective surfaces