High-efficiency continuous surface-relief gratings for two-dimensional array generation.

Continuous surface-relief phase gratings for two-dimensional (2-D) array generation have been realized by laser-beam writing lithography. For a 9 x 9 fan-out element, a diffraction efficiency of 94% and a uniformity of better than +/-8% have been achieved. These are, to our knowledge, the best published results for 2-D surface relief fan-out elements. Separable and nonseparable solutions for the design of 2-D fan-out elements are discussed.