3D lithography of diamond thermal emitters for microscale emissivity control.

On-demand control of material emissivity presents a compelling avenue for innovating both fundamental research and engineering applications. However, a solution for high-precision, wide range, and multi-degree-of-freedom emissivity modulation remains an unmet challenge. Here, we demonstrate programmable absorptive microcavity arrays within bulk diamond using a minimalist ultrafast laser-induced composite micro-nanostructuring approach. These microcavities incorporate amorphous layers and numerous random nanostructures, exhibiting exceptional broadband emissivity (reaching ~0.97 across 0.25-25 μm). By tuning the structural characteristics of the microcavities, we demonstrate pixel-level microscale emissivity manipulation within the diamond matrix. The engineered thermal emitters enable multiple advanced performances: high resolution, fast response, angular independence, and remarkable stability. These findings unlock diverse brand-new applications, including 3D thermal displays, thermal encryption, and multi-dimensional information recording. Our methodology represents a new paradigm for establishing a versatile thermal radiation management platform in a highly transparent medium, bridging the gap from 2D on-surface towards 3D free-space emissivity engineering for next-generation thermal-photonics technologies.