Laser Turrets use Light Amplification by Stimulated Emission of Radiation (LASER, get it?) which excites large numbers of electrons within a ruby crystal or other lasing medium into an energized state that can sustain a coherent, radiant light beam which is then chirped into short, femtosecond, ultra-dense pulses of energy. When these pulses hit attacking ships, its heat melts the outer armour to destroy it.
Still a relatively basic defense, but sometimes enough to scare away low-level attackers from your base. Again, many players will move on from deploying these turrets relatively quickly in the game, and these defenses are largely avoided by base owners.