A laser output coupler (OC) is a component of an optical resonator that allows the extraction of a portion of the light from the laser’s intracavity beam. It most often consists of a partially reflective mirror, allowing a certain portion of the intracavity beam to transmit through.
An output coupler is typically a partially reflective mirror that is placed at one end of the laser cavity. As the light circulates within the laser cavity, a portion of it is transmitted through the output coupler, while the rest is reflected back into the cavity to continue circulating. The amount of light transmitted through the output coupler is determined by its reflectivity, which can be adjusted to optimize the laser’s performance.