Tandem of surface relief holographic gratings as a multiple-beam splitter

A new type of 1 x 9 multiple-beam splitter making use of two surface relief holographic gratings in stack is reported. The grating periods differ by a factor of three and the zero and ii diffraction orders generated by either grating on normal or slightly oblique incidence of a plane wave have nearly identical diffraction efficiencies. The fundamental feature of the design is the quoted ratio between grating periods rather than the specific choice of the profile shape. Splitters which generate nine beams (diffraction orders) bearing about 90% of the total output power with less than 4% non-uniformity in their diffraction efficiencies were achieved. Possible extension to 9 x 9 multiple-beam splitting using a tandem of crossed gratings is addressed, too.