MetaHeat: Programmable Photothermal Heating in Complex Media with Inverse-Designed Metasurfaces

Precise spatial control of light-induced heating is critical across photothermal applications ranging from laser therapies to materials processing yet remains difficult in the presence of complex refractive interfaces. For example, laser warming of cryopreserved specimens requires uniform, rapid heating, but refractive distortions produce damaging thermal gradients that compromise viability. We present MetaHeat, a metasurface-based wavefront engineering framework for programmable photothermal heating in complex media. MetaHeat addresses the coupled challenge of light propagation and subsequent heat transport by combining angular-spectrum wave propagation with transient diffusion in a unified, differentiable framework. Applied to laser warming, MetaHeat navigates a high-dimensional metasurface design space─with thousands of meta-atoms─constructing wavefronts that suppress hot and cold spots, reducing spatial temperature variance by over an order of magnitude (≈31×) in a representative target. We observe similar improvements in additional geometries, suggesting the approach is general and provides a route to programmable photothermal heating in complex refractive media.