Nonlinear transmission of CO2 laser radiation by graphene

The nonlinear transmission of multilayer (~12 layers) graphene at the wavelength λ ~10 μm is measured for the first time. The absorption saturation intensity in graphene (~330 kW cm^-2) and the ablation threshold of its outer layers (~1 MW cm^-2, 0.11 J cm^-2) under action of a CO₂ laser pulse with a duration of 70 — 85 ns at λ = 10.55 μm are determined. The residual absorption of graphene at its partial saturation was 48 % of the initial value. This is significantly smaller than the value measured previously for samples with a close number of layers at λ = 1.55 μm (92.3 % — 93.8 %). It is shown that the ablation threshold of two graphene layers adjacent to the BaF₂ substrate (after successive ablation of outer layers) exceeds 0.27 J cm^-2.