What is the purpose of the optical cavity in a laser?

The optical cavity in a laser serves the critical function of amplifying light. This cavity typically consists of two mirrors placed at each end, forming a resonant optical cavity where light can bounce back and forth. When the gain medium inside the cavity is excited, it emits photons. As these photons reflect between the mirrors, they stimulate further emissions from other excited atoms or molecules in the gain medium, leading to a process known as stimulated emission. This amplification process is essential for producing a coherent and intense laser beam.

While there are various elements of a laser's design that may focus or shield light, these aspects do not capture the fundamental role of the optical cavity, which is primarily focused on enhancing the intensity of the light through amplification. The other choices refer to different functionalities that are not the primary purpose of the optical cavity in the laser system.