Wavefront-modulated four-wave mixing interferometry with silicon checkerboard gratings

Nonlinear optical FWM generation was studied using a wavefront-modulated beam to understand how emissions adapt under additional interference. Size-dependent circular π-phase-modulated masks were applied to create stepwise, z-directionally elongated, bottleneck-shaped FWM foci as schematic interference conditions. The polarizing FWM features varied dramatically as the circular mask size approached 0.35 times the beam barrel, resulting in the convergence of two inherently paired emissions without significant contrast at the edges. The results were reproduced through kernel-type filtering using two-dimensional nonlinear spatial filters with computationally efficient focal field calculations.