Shaping partially coherent light by the coherent mode decomposition

The coherence properties of light are essential when it comes to its modulation, and light of partial coherence in particular demands special attention compared to fully coherent light. Designs for the latter have been favored by the compact platforms driving research into the manipulation of light at the microscale and below, such as photonic crystals, plasmonics, and metasurfaces. The assumption of a spatially coherent input, while appropriate for many applications, leaves aside the very useful and common class of partially coherent light sources. Schemes for shaping partially coherent light have emerged, but their capacity for arbitrary field engineering is limited compared to more mature work with coherent inputs. Here we explore the coherent mode decomposition (CMD) as a way to treat partially coherent sources that enables the use of coherent design techniques even when working with partial coherence. To do so, we coherently address the modes of the decomposition to create a hologram from a partially coherent source, and also quantify the degree of coherence at which our technique becomes essential. (c) 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement