Ultra‐Broadband Plane Blackbody by Ultrafast Laser Induced Surface Hierarchical Structuring and Nanodefect Engineering

Blackbodies, ideal light-absorbing objects per Planck's law, do not occur in nature on Earth. Nevertheless, they are of utmost significance in applications across astronomy, optoelectronics, and thermal radiation engineering. While artificial counterparts such as cavity blackbodies and plane blackbodies can approximate ideal blackbodies to some extent, they are beset with problems, including large volume, low emissivity, narrow bandwidth, poor uniformity, and feeble adhesion. Here, a method relying on ultrafast laser direct irradiation is reported, which enables fast writing of uniform plane blackbodies with high-emissivity over 0.98 in an ultra-broadband spectrum of 3-14 µm on a doped silicon surface. A phenomenon of energy negative feedback regulation in laser-material is discovered, which allows for the simultaneous implementation of hierarchical surface structuring and nanodefect-induced energy-level engineering. The resulting micro-nano hierarchical cone-array structure effectively curbs light back-scattering and intensifies nanodefect-induced absorption. Since the laser-treated surface does not entail material adhesion or injection, it exhibits superior stability in contrast to traditional black coatings. This is corroborated by high-temperature tests exceeding 900 °C and repeated mechanical exfoliation tests, underscoring its resilience in harsh environmental conditions.