Exploring optomechanical metamaterials for stray-light control

General methods for stray light suppression typically involve choosing material properties, geometrical configurations, and surface topographies. Designing optical systems necessitates careful balancing of conflicting requirements, such as minimising size and weight while simultaneously improving heat transfer and reducing stray light from illuminated peripheral mounting surfaces. Stray light is typically mitigated by apertures, coatings, and microscopic structures, alongside maintaining cleanliness. However, using apertures may not always be feasible, and effective optical absorber coatings or microscopic light absorbing structures can be costly and sensitive to environmental factors such as abrasion, radiation heating, or cleaning agents. Bio-inspired, macroscopic foam- and sponge-like geometries, “macroscopic structural light absorbers”, have been explored for their potential in reducing stray light, without requiring modifications to a surface coating. In a proof-of-concept study, exemplary structures demonstrated significant effectiveness, with reflected peak intensities reduced by factors below 0.39 and average intensities by factors below 0.65 compared to an unstructured reference. With the proposed mechanical metamaterials, engineering designers can balance structural and surface durability, residual stray light propagation directions, weight, stiffness, heat transfer and thermal expansion. Additive techniques such as powder bed fusion or fused deposition modelling enable sustainable fabrication. The approach offers robust, cost-effective absorbers made from durable materials like black anodised aluminium or ABS polymers, among others.