A laser differs from other sources of light in that it emits light that is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as optical communication, laser cutting, and lithography. It also allows a laser beam to stay narrow over great distances (collimation), a feature used in applications such as laser pointers, lidar, and free-space optical communication. Lasers can also have high temporal coherence, which permits them to emit light with a very narrow frequency spectrum. Temporal coherence can also be used to produce ultrashort pulses of light with a broad spectrum but durations as short as an attosecond.
A laser differs from other sources of light in that it emits light that is coherent Spatial coherence allows a laser to be focused to a tight spot enabling applications such as optical communication laser cutting and lithography It also allows a laser beam to stay narrow over great distances (collimation) a feature used in applications such as laser pointers lidar and free-space optical communication Lasers can also have high temporal coherence which permits them to emit light with a very narrow frequency spectrum Temporal coherence can also be used to produce ultrashort pulses of light with a broad spectrum but durations as short as an attosecond