A surface treating method and apparatus include operating a quasi-continuous wave fiber laser and pre-scan shaping the laser beam such that an instantaneous spot beam has predetermined geometrical dimensions, intensity profile, and power; operating a scanner at an optimal angular velocity and angular range to divide the pre-scan beam into a plurality of sub-beams deflected towards the surface being processed; guiding the sub-beams through a post-scan optical assembly to provide the spot beam with predetermined geometrical dimensions, power, and angular velocity and range, which are selected such that the instantaneous spot beam is dragged in a scan direction over a desired length at a desired scan velocity, which allow the treated surface to be exposed for a predetermined exposure duration and have a predetermined fluence distribution providing the treated surface with a quality comparable to that of the surface processed by an excimer laser or a burst-mode fiber laser.