Suppose you have an application that needs very short laser pulses (like telecom) — to get pulses faster than can be produced by using electronics to switch the laser on and off, you need a passively mode-locked laser. Like a “dippy bird, optical power builds up and up in the laser cavity until a threshold is reached and a pulse is emitted. Then the process begins again.
So mode-locking is really useful for fast pulses, but we would also like to apply mode-locking to tiny lasers, so that we can fit them into more equipment. And that’s pretty much what an international group of researchers has done: developed a new mode-locking method that lets them make smaller — potentially much smaller — lasers that are both ultrafast and stable.
Read more about it in my story for OPN: Mode-Locking Method Shows Stable Output, Potential for Tiny Lasers.