Complex refractive index and extinction performance of graphene in infrared bands

As a new type of two-dimensional nano-carbon material, graphene has great potential application value in infrared interference, and its infrared extinction characteristics are worthy of in-depth study. In this paper, the ellipsometric parameters of graphene pellet in the infrared bands were measured by infrared ellipsometry, and the complex refractive index was calculated. Subsequent, the relationships between efficiency factors, extinction coefficient and the incident wavelength, diameter, thickness in 2-14 μm wavebands of graphene particles were calculated with discrete dipole approximation (DDA) method. Results show that graphene has excellent infrared extinction performances in 2-14 μm wavebands, and the extinction performance of the particles to near-infrared and mid-infrared radiation is better than that of far-infrared band. The extinction performances mainly depend on the absorption properties of the particles, and the absorption is better than the scattering effect. The extinction efficiency factor and extinction coefficient gradually decrease with the increase of wavelength. The extinction efficiency factor increases with the increase of the particle's diameter. The extinction coefficient in near-infrared and middle-infrared bands is better than that in far-infrared bands, of which the particles with diameter of 0.25-1 μm have the largest extinction coefficient. The extinction coefficient of the particles with diameter of 1-4 μm decreases slowly with the increase of diameter, while the extinction ability of particles with diameter larger than 4 μm is little affected by the change of particle size. The extinction efficiency factor gradually increases with the increase of the thickness of graphene sheet, the extinction coefficient in near-infrared and middle-infrared bands decreases with the increase of the thickness, while the extinction coefficient in far-infrared bands is less affected by the change of particle thickness.