Mode-locking

Mode-locking is a way to make a laser beam shoot out lots of short pulses instead of one long beam. Imagine you have a toy car that you want to race along a track as fast as possible. One way to do this is to push it very hard all at once, but it will slow down quickly and not go very far. Another way is to push it just a little bit at a time, but really quickly. This way it will keep going fast for longer and travel further.

Now, lasers work in a similar way. They can either shoot out one long beam or shoot out many short beams. When we want many short beams, we use something called a mode-locker. The mode-locker is like a tiny machine that flicks a switch really fast. This switch turns the laser off and on so quickly that the beam comes out in a series of short pulses. This makes the laser really powerful and useful for lots of things like cutting, welding, and even medical procedures. So, mode-locking is like making your laser toy car zoom really fast and travel further with lots of little pushes instead of one big push.