Mode-locked is a research area in the field of optics and photonics that involves the synchronization of different longitudinal modes of a laser to produce short pulses of light with extremely high peak powers and very short durations. This technique is used in a variety of applications, including ultrafast spectroscopy, telecommunications, and laser surgery. Mode-locked lasers are capable of generating pulses with durations on the order of picoseconds or femtoseconds, making them invaluable tools for studying ultrafast processes in materials and biological systems. The ability to control the timing and intensity of these ultrafast pulses has opened up new possibilities for a wide range of applications in science, technology, and medicine.