Laser linewidth

Laser linewidth is the spectral linewidth of a laser beam.

Two of the most distinctive characteristics of laser emission are spatial coherence and spectral coherence. While spatial coherence is related to the beam divergence of the laser, spectral coherence is evaluated by measuring the laser linewidth of the radiation. Although the concept of laser linewidth can have varied theoretical descriptions here, this article provides a simple experimental description. One of the first methods used to measure the coherence of a laser was interferometry. An alternative approach is the use of spectrometry.