Chinese have developed and are testing the Dong Feng 21D missile, capable of accurately targeting and hitting a moving navy Aircraft Carrier from 2000 miles away. US experts are scared. Since capabilities of this missile are not fully known to US Navy, their strategy to combat it currently is SM-3 interceptor rockets launched from Aegis destroyers and cruisers that escort Aircraft Carriers.
Problem with that is that the reloading capacity of these Aegis equipped ships isn't fast enough to protect against a volley of Dong Feng 21Ds. So they are pretty much screwed. Currently Aircraft Carriers are the most effective way of projecting current US air superiority anywhere in the world. Imagine the implications of a bunch of US carriers being sunk.
This laser defense system may be Navy's answer to this new missile threat.