Spectrally pure lasers lie at the heart of precision high-end scientific and commercial applications, thanks to their ability to produce near-perfect single-color light. A laser’s capacity to do so is measured in terms of its linewidth, or coherence, which is the ability to emit a constant frequency over a certain period of time before that frequency changes.

Original source: https://www.sciencedaily.com/releases/2019/02/190201142346.htm