Embedded Effective-Index-Material in Oxide-Free Hybrid Silicon Photonics Characterized by Prism Deviation

Hybrid silicon photonics offers novel opportunities to control light propagation with nanostructured media on the silicon side. In the specific case of oxide-free heteroepitaxial bonding of III-V layers on silicon, it is particularly crucial to assess the role of nanostructures in the post-bonding situation. We propose here a method of internal light source and integrated prism deviation to evaluate the effective index of small sub-wavelength periodic shallow holes that are completely embedded and do not lend themselves to alternative such as e.g. ellipsometry. We achieve a precision Δn <; 0.01, a good accuracy both for the understanding and optimization of optical components performances. Measured data are in good agreement with the theoretical expectation, as obtained using an improved homogenization strategy and further confirmed by 3D Bloch mode calculation.