Abstract

Low spatial frequency gratings (i.e., Raman-Nath diffraction regime) exhibit multiple diffracted waves excited by a single incident plane wave. The energy distribution among the diffracted waves depends on the magnitude of the modulation and on the grating shape. For some applications, it is of interest to produce structures which support multiple diffracted waves with approximately equal intensities. Periodic arrays of dielectric cylinders were reported to have this property.¹ In this paper, surface relief structures with conic (elliptic, hyperbolic, and parabolic) cross-sectional grating shapes are studied as an extension of this work. Better uniformity in the intensity distribution among the orders compared with dielectric cylinders is possible. In particular, a variable number of fairly evenintensity diffracted orders with reasonably sharp cutoff is found to be obtainable. Integral expressions, based on simple transmittance theory, are given for the complex amplitudes of the diffracted waves. These expressions are evaluated using an exact rigorous coupled wave theory² and experiments. Potential applications include elements in multiple imaging, optical interconnection of networks and devices in integrated optics and communication systems, machine vision, as well as general beam division.

© 1989 Optical Society of America