What is an "optical cavity" in a laser?

An optical cavity in a laser refers to the space between mirrors where laser light is amplified. This cavity plays a crucial role in the functioning of a laser. It contains at least two mirrors positioned facing each other, which help to enhance the light produced by the lasing medium. When light is emitted from the excited atoms or molecules in the medium, it travels back and forth between the mirrors. As it reflects, it passes through the medium multiple times, stimulating further emissions and leading to a build-up of coherent light. This process is essential for achieving the desired laser output.

The other options refer to different elements or components associated with laser technology, but they do not accurately describe the optical cavity's function. A device converting electrical energy to laser energy pertains more to the power supply or pump mechanism rather than the cavity itself. A lens system focusing laser beams is related to beam shaping and directing the produced laser light after it exits the cavity. Lastly, a cooling system is essential in maintaining optimal operating conditions for high-powered lasers but does not define the optical cavity's purpose or structure.