Effective optical properties of supported silicon nanopillars at telecommunication wavelengths

• Published in: Optics communications Vol. 399; pp. 127 - 134
• Main Authors: Pérez-Chávez, V., Simonsen, I., Maradudin, A.A., Blaize, S., Méndez, E.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2017
• Subjects: Effective medium theory; High index dielectrics; Light scattering; Optical metamaterials; Silicon photonics; Transformation optics; Transformation optics; Silicon photonics; Effective medium theory; Optical metamaterials; Light scattering; High index dielectrics
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2017.04.027

We measure and calculate the optical response of a structure consisting of a square array of subwavelength silicon posts on a silicon substrate at telecommunication wavelengths. By the use of the reduced Rayleigh equations and the Fourier modal method (rigorous coupled wave analysis) we calculate the reflectivity of this structure illuminated from vacuum by normally incident light. The calculated reflectivities together with experimentally determined ones, are used to test the accuracy of effective medium theories of the optical properties of structured silicon surfaces, and to estimate the effective refractive index of such surfaces produced by a homogeneous layer model. •We test the effective medium concept for thin layer of subwavelength silicon pillars.•The study is based on rigorous calculations and experiments with fabricated samples.•Effective medium theories fail to reproduce the experimental and theoretical results.•We find that a layer of silicon pillars cannot be modeled as a homogeneous layer.•The failure may be due to the large dielectric contrast between silicon and air.