Most communications today are done using one frequency or another in the radio part of the electromagnetic spectrum. However, the communication bandwidth is proportional to the frequency of the exelctromagnetic wave used for communication. Lasers operate are higher frequencies than radio waves so their bandwidth is higher - much higher - than radio frequncy (RF) communications.
Laser communications (LaserCom) have to contend with issues ranging from platform disturbances to atmospheric attenuation. The purpose of LaserCom is to get fiber optic bandwidth without having to run fiber. This requires disturbance rejection that is good enough to put a laser from a distant source down a fiber optic cable. This requires high bandwidth stabilization and thermally stable optical platforms.