Abstract

Planar dielectric gratings for beam coupling and other functions are usually regarded as configurations suitable for uses requiring relatively narrow frequency ranges. However, an accurate perturbation analysis reveals that such periodic configurations can be designed to operate as beam couplers over a wavelength range that can be as high as 2:1. In particular, the beams radiated by an output coupler may scan over large angular regions, but their widths remain fairly constant over that entire wavelength range. Analogous considerations hold for gratings that serve as input couplers. We find that it is also possible to shape the grating profile to achieve blazing effects such that only a single output or input beam is effectively involved over the same broad wavelength range. Dielectric grating configurations can thus be designed so that they exhibit both broadband and high efficiency characteristics.

© 1991 Optical Society of America