Editing Mode locking (section)

{{Short description|Way to produce very short laser bursts}}
{{Use American English|date = March 2019}}
{{other uses|Arnold tongue|Inharmonicity#Mode-locking}}
{{no footnotes|date=December 2021}}
'''Mode locking''' is a technique in [[optics]] by which a [[laser]] can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10<sup>−12</sup>&nbsp;s) or femtoseconds (10<sup>−15</sup>&nbsp;s). A laser operated in this way is sometimes referred to as a '''femtosecond laser''', for example, in modern [[refractive surgery]]. The basis of the technique is to induce a fixed [[phase (waves)|phase]] relationship between the [[longitudinal mode]]s of the laser's [[resonant cavity]]. [[Wave interference|Constructive interference]] between these modes can cause the laser light to be produced as a train of pulses. The laser is then said to be "phase-locked" or "mode-locked".