Embodiments of the present disclosure include a optical assembly comprising: an axicon lens with spherical aberration configured to generate the laser beam focal line, an optical element set spaced part from the optical lens, and a focusing optical element spaced apart from the optical element set, wherein the axicon lens and the optical element set are translatable relative to each other along the laser beam propagation direction and wherein the focusing optical element is in a fixed position along the laser beam propagation direction.