An optical element comprising a window formed of synthetic diamond material and an optical surface pattern formed directly in a surface of the synthetic diamond material. The window of synthetic diamond material is in the form of a wedged diamond window with non-parallel major surfaces defining a wedge angle in a range (1) arcminute to 10° and the optical surface pattern is formed directly in one or both of the non-parallel major surfaces. There is also described a laser system comprising the optical element and a laser having a coherence length, wherein the coherence length of the laser is greater than twice a thickness of the wedged diamond window at its thickest point.