A variable astigmatic focal beam spot is formed using lasers with an
anamorphic beam delivery system. The variable astigmatic focal beam spot
can be used for cutting applications, for example, to scribe
semiconductor wafers such as light emitting diode (LED) wafers. The
exemplary anamorphic beam delivery system comprises a series of optical
components, which deliberately introduce astigmatism to produce focal
points separated into two principal meridians, i.e. vertical and
horizontal. The astigmatic focal points result in an asymmetric, yet
sharply focused, beam spot that consists of sharpened leading and
trailing edges. Adjusting the astigmatic focal points changes the aspect
ratio of the compressed focal beam spot, allowing adjustment of energy
density at the target without affecting laser output power. Scribing
wafers with properly optimized energy and power density increases
scribing speeds while minimizing excessive heating and collateral
material damage.