Generalized Phase Contrast (GPC) is an efficient method for efficiently shaping light into speckle-free contiguous
optical distributions useful in diverse applications such as static beam shaping, optical manipulation and recently, for
excitation in two-photon optogenetics. GPC typically results in a 3x intensified user defined input mask shape against a
dark background. In this work, we emphasize GPC’s capability of optimal destructive interference, normally used to
create the dark background surrounding the shaped light. We also study input parameters wherein the locations of light
and darkness are interchanged with respect to typical GPC output, thus resulting to a well-defined structured darkness.
The conditions that give destructive interference for the output are then applied to near-arbitrary shapes. Preliminary
experimental results are presented using dynamic spatial light modulator to form scaled arbitrary darkness shapes.
Supporting demonstrations that reverse the light and dark regions of amplitude-modulated input are also presented as a
related case of structuring destructive interference. Our analysis and experimental demonstrations show a simplified
approach in the generation of extended regions of destructive interference within coherent beams.