What does the term "mode" refer to in the context of laser physics?

In laser physics, the term "mode" specifically refers to a specific pattern of standing waves that can exist within the laser cavity. These standing waves represent the spatial distribution of the electromagnetic field inside the cavity, which contributes to the laser's characteristics, such as its beam quality and output.

When a laser operates, it can support multiple modes simultaneously, depending on the design of the cavity, the gain medium, and other factors like the wavelength of the emitted light. Each mode corresponds to a particular resonant frequency and shape, which is essential in determining how the laser beam propagates. The fundamental mode is usually the most stable and has the best beam quality, while higher-order modes can lead to more complex output patterns.

Understanding the concept of modes is crucial for mastering laser operation and design, as it directly affects performance metrics such as coherence, divergence, and intensity distribution.