Interferometric amplitude apodization of integrated gratings.

Modern photolithography with its sub-hundred-nanometer-scale resolution and cm-scale spatial coherence provides for the creation of powerful waveguide diffractive structures useful as integrated spectral filters, multiplexers, spatial signal routers, interconnects, etc. Application of such structures is facilitated by a lithographically friendly means of amplitude apodization, which allows for programming of general spectral and spatial transfer functions. We describe here an approach to implementing flexible binary-etch-compatible diffractive amplitude control based on the decomposition of diffractive structures into subregions each of whose diffractive contours are spatially positioned so as to interferometrically control the net diffractive amplitude and phase of the subregion. The present approach is uniquely powerful because it allows for substantial decoupling of amplitude and phase apodization.