Mode-locked lasers are a type of laser that produces very short pulses of light, typically in the picosecond or femtosecond range. This is achieved by locking multiple longitudinal modes of the laser together, allowing them to interfere constructively at regular intervals. The result is a series of high-intensity light pulses that can be used in various applications, including telecommunications and medical imaging. These lasers are essential in fields like optical communication and ultrafast spectroscopy, where precise timing and high peak power are crucial. By generating short bursts of light, mode-locked lasers enable scientists to study fast processes, such as chemical reactions and electron dynamics, with remarkable detail.