Diagnosis of a periodic nanostructure with a defect using circularly polarized light

The paper considers the reflection of a circularly polarized light wave from a periodic nanostructure. The method of characteristic matrices was used to calculate the ellipsometric parameters ρ 0 and Δ of reflected light. It is shown that a wave initially polarized in the left circle changes polarization upon reflection, turning into an elliptically polarized wave. The results obtained for an ideal periodic medium are compared with the results of reflection from a periodic medium with a single defect - the upper layer of the original periodic medium is replaced by an absorbing dielectric layer. The analysis showed that the spectral dependences of the ellipsometric parameters for two structures, periodic and defective, differ significantly. In the range of wavelengths λ from 0.4 μm to 0.6 μm, the ellipsometric parameter ρ 0 for the considered periodic medium and the medium with a defect differ significantly from each other - where the maximum is for one medium, there is approximately the minimum for the other. In turn, the parameter Δ demonstrates a significant difference for the two structures in the wavelength range λ from 0.46 μm to 0.55 μm. The use of circularly polarized light demonstrates wide possibilities for studying defects in periodic nanostructures.