Antireflective Properties of Polystyrene Nanosphere Self-Assembled Films
V. CÂNPEAN, C. FARCĂU, E. VINŢELER, S. AŞTILEAN

Abstract.
In this work we examined the antireflective properties, in the visible and near-infrared (NIR) range, of polystyrene nanospheres self-assembled films deposited on glass substrate by convective assembly. For incident light of wavelength larger that the diameter of spheres, the two-dimensional (2D) colloidal crystal cannot be resolved by the incident light and the structure acts as a continuous film with graded refractive index along the z-axis. In this case we found the film exhibits a clear antireflective ef-fect. For incident light of shorter wavelength this is not the case and the structure acts as a simple diffraction grating, the incident light  being distributed either into propaga-tive or waveguided diffracted orders. We simulated the transmission and reflectivity of such structures by using finite-difference time-domain (FDTD) method and found good agreement with the measurements.