What does “beam divergence” refer to in laser optics?

Beam divergence in laser optics describes how much a laser beam spreads out or expands as it travels away from its source. This phenomenon is a crucial characteristic of laser beams. When a laser is emitted, it ideally presents as a collimated, highly focused beam with minimal spread. However, due to the inherent properties of light and the specific design of the laser, the beam will gradually diverge over distance, meaning that it will spread out and occupy a larger area.

The measure of beam divergence is often expressed in terms of angles, such as milliradians, which quantify how rapidly the beam expands from its initial diameter. A smaller divergence angle indicates that the beam remains more focused over longer distances, making it suitable for applications where precision is required, such as in laser cutting or medical procedures.

Understanding beam divergence is essential for applications that rely on the effective use of laser technology, as it affects the intensity and focus of the beam over distance. This is why option B accurately captures the definition of beam divergence in laser optics.