Laser apparatus for cutting brittle material, the brittle material having an entrance surface and an exit surface, the apparatus comprising: a laser-source delivering a collimated beam of pulsed laser-radiation, the pulsed laser-radiation having a pulse duration of less than about 20 picoseconds; an aspheric focusing lens having an optical axis and a clear aperture; and being characterised by: a beam-expanding element located in the collimated beam of pulsed-laser-radiation between the laser-source and the aspheric focusing lens, the beam-expanding element forming the collimated beam of pulsed laser-radiation into an expanded beam of pulsed laser-radiation, the expanded beam of pulsed laser-radiation overfilling the clear aperture of the aspheric focusing lens such that only a portion of the expanded beam of pulsed laser-radiation is inside and fills the clear-aperture; wherein in use, focusing of the portion of the expanded beam of pulsed laser-radiation inside the clear aperture by the aspheric focusing lens in combination with diffraction by the clear aperture forms a focused beam of pulsed laser-radiation having an elongated focus, the elongated focus having a substantially uniform intensity distribution along the optical axis; and wherein the elongated focus overlaps the brittle material between the entrance surface and the exit surface, wherein the clear aperture of the aspheric focusing lens is defined by a discrete aperture, which is located between the beam-expander and the aspheric focusing lens, and physically blocks the peripheral rays, or the clear aperture is defined by the edge of the aspheric focusing lens, which is an optical edge thereof or a physical edge thereof. a laser-source delivering a collimated beam of pulsed laser-radiation, the pulsed laser-radiation having a pulse duration of less than about 20 picoseconds; an aspheric focusing lens having an optical axis and a clear aperture; and being characterised by: a beam-expanding element located in the collimated beam of pulsed-laser-radiation between the laser-source and the aspheric focusing lens, the beam-expanding element forming the collimated beam of pulsed laser-radiation into an expanded beam of pulsed laser-radiation, the expanded beam of pulsed laser-radiation overfilling the clear aperture of the aspheric focusing lens such that only a portion of the expanded beam of pulsed laser-radiation is inside and fills the clear-aperture; wherein in use, focusing of the portion of the expanded beam of pulsed laser-radiation inside the clear aperture by the aspheric focusing lens in combination with diffraction by the clear aperture forms a focused beam of pulsed laser-radiation having an elongated focus, the elongated focus having a substantially uniform intensity distribution along the optical axis; and wherein the elongated focus overlaps the brittle material between the entrance surface and the exit surface, wherein the clear aperture of the aspheric focusing lens is defined by a discrete aperture, which is located between the beam-expander and the aspheric focusing lens, and physically blocks the peripheral rays, or the clear aperture is defined by the edge of the aspheric focusing lens, which is an optical edge thereof or a physical edge thereof. a beam-expanding element located in the collimated beam of pulsed-laser-radiation between the laser-source and the aspheric focusing lens, the beam-expanding element forming the collimated beam of pulsed laser-radiation into an expanded beam of pulsed laser-radiation, the expanded beam of pulsed laser-radiation overfilling the clear aperture of the aspheric focusing lens such that only a portion of the expanded beam of pulsed laser-radiation is inside and fills the clear-aperture; wherein in use, focusing of the portion of the expanded beam of pulsed laser-radiation inside the clear aperture by the aspheric focusing lens in combination with diffraction by the clear aperture forms a focused beam of pulsed laser-radiation having an elongated focus, the elongated focus having a substantially uniform intensity distribution along the optical axis; and wherein the elongated focus overlaps the brittle material between the entrance surface and the exit surface, wherein the clear aperture of the aspheric focusing lens is defined by a discrete aperture, which is located between the beam-expander and the aspheric focusing lens, and physically blocks the peripheral rays, or the clear aperture is defined by the edge of the aspheric focusing lens, which is an optical edge thereof or a physical edge thereof.