Enhanced near-infrared saturable absorption via carbon black SiO ₂ core-shell nanostructures

Infrared laser anti-reflection devices can significantly reduce light loss, improve the energy utilization efficiency of laser systems, reduce impurity of light interference, and enhance imaging clarity by optimizing the anti-reflection performance of optical devices. The reflection enhancement of the carbon black (CB)/cycloolefin copolymer (COC) material in the near-infrared region driven by nonlinear saturable absorption (SA) was investigated. In this work, a CB@SiO 2 core-shell structure was designed and added into the COC matrix to prepare the composites. The open-aperture Z scan was performed at 1064 nm using a picosecond pulsed laser to evaluate the optical nonlinearity. The results show that the silica layer significantly enhances the saturation absorption performance of carbon black and its composites. At low energy density, the maximum normalized transmittance of SiO 2 -coated composites reaches 222%. This enhancement is attributed to the electron capture at the SiO 2 -CB interface, highlighting the potential of CB-based materials in near-infrared anti-reflection applications.