
The amount of energy delivered by a laser beam per unit time.Laser power is the rate at which a laser beam delivers energy, typically measured in watts. It ranges from milliwatts in everyday devices like barcode scanners to petawatts in the most powerful research lasers, which can briefly outshine the entire Sun's output focused onto a tiny spot. The power determines how a laser interacts with matter: low-power beams can read or write data, while high-power beams can cut steel, fuse plasma, or accelerate particles.
The first working laser, built by Theodore Maiman in 1960, produced a pulsed beam of about 1 kilowatt for a fraction of a millisecond. Since then, power levels have grown by many orders of magnitude, with chirped-pulse amplification, developed in the 1980s, enabling the petawatt regime.
Laser power is set by the gain medium's ability to amplify light and the pumping mechanism that supplies energy. Continuous-wave lasers emit a steady beam, while pulsed lasers concentrate energy into short bursts, achieving enormous peak powers even with modest average power. The beam's power density—watts per square centimeter—is what actually drives effects like heating, ionization, or nonlinear optical phenomena, so focusing a beam tightly can dramatically increase its intensity.
Laser power is exploited in industrial cutting and welding, medical surgery, laser fusion experiments, and precision measurements like LIGO's gravitational wave detectors, where even tiny power fluctuations matter.
The most powerful continuous-wave laser, used in military research, can melt through steel at a distance of over a kilometer, yet its beam is invisible to the naked eye.






