Laser Power The total output power of a laser is the total result of all built in laser sources combined. This power is measured in mW (Milliwatts) or W (Watts).The power specification can be given "before" or "after" optics. "Before" means directly at the laser sources, "after" means measurement after the laser aperture.Values given "after optics" / "after aperture" already comprise power loss due to optical components.