Laser protection technologies based on nonlinear absorption colloidal suspension

With the increasing threat of soft-kill laser weapons to military optoelectronic systems, there is an urgent need for nonlinear laser protection technologies that combine high performance, long-term stability, environmental robustness, and operational sustainability. Conventional laser protection materials, whether liquid-based or solid-state, suffer from critical shortcomings including poor stability, low damage thresholds, limited environmental adaptability, and lack of recyclability. Here, we report a colloidal suspension based nonlinear laser protection system that overcomes these limitations. Using magnetic graphene oxide (MGO) dispersed in a high-viscosity, water-soluble polyethyleneimine medium, the system achieves exceptional stability (no sedimentation for over two months), a high laser damage threshold (>1.2 J/cm 2 ), and green recyclability via magnetic recovery. At a concentration of 0.0219 mg/mL, the MGO colloidal suspension exhibits a minimum transmittance of 22.7% and an NOL capacity coefficient of 0.385 at 1064 nm. Its protective performance exceeded that of many existing NOL materials. The nonlinear absorption coefficients measured by Z-scan experiments reach up to 1.69×10 −9 m/W. Furthermore, the material maintains stable performance at elevated temperatures (up to 75 °C) and after extended storage. This work demonstrates that colloidal suspensions represent a new class of practical laser protection media, offering a promising solution for defending military platforms against soft-kill laser threats.