Diffraction of Partially Coherent Light as a Nonlinear Operation

The linear transformation of optical fields during propagation poses a fundamental limitation for neuromorphic computing applications. In this paper, a realization of a nonlinear operator based on the diffraction of partially coherent light by an aperture partially covered with a binary phase grating is proposed. The dependence of the effective aperture width on the spatial coherence of the incident light produces a nonlinear behavior that formally introduces a nonlinear integration kernel into the propagation integral. The proposed concept is validated through numerical experiments performed using the PyWolf framework for partially coherent light propagation modeling. This coherence-induced nonlinearity, which effectively implements a nonlinear propagation kernel with an input-dependent transfer function, offers a viable pathway to overcome the limitations of purely linear diffractive networks and can be leveraged for constructing multilayer architectures.