A diffractive element used in conjunction with a grating to move a desired order
beam off-axis, thereby reducing interference by undesired orders. Use of the off-axis
grating allows a more uniform beam in the presence of manufacturing defects, such
as etch depth errors. The diffractive element used with the off-axis grating may
include a beam shaper, a one-dimensional beam splitter, or a two-dimensional beam splitter.
