A phase plate and lens modify light beams emitted by an array of lasers to form an efficient illumination source for a MEMS light modulator array. The phase of the electric field emitted by the lasers is modified such that the after passing through a lens the beam profile at the lens focal plane has an approximately rectangular shape appropriate for illuminating a light modulator array. The phase plate may be constructed from a glass plate with rectangular notches etched in it or with rectangular ridges formed on it. Furthermore a light source, such as a laser, may be coupled to an adiabatically tapered optical waveguide in which a phase adjusting block is introduced in analogy to notches in a bulk phase plate. Phase modified light beams output from the waveguide system have similar focusing properties to those passing through a bulk phase plate.