Silicon-on-insulator based quasi 3D photonic crystal structures

A new kind of substrate called Silicon-On-Mirror has been fabricated for nanophotonics applications. It is composed of a monocrystalline silicon layer separated from the silicon substrate by a buried distributed Bragg reflector. Photoluminescence of silicon at 80 K is used to investigate two-dimensional (2D) photonic crystal hexagonal microcavities etched in the monocrystalline silicon layer. Two types of substrates are compared: silicon-on-insulator (SOI) substrates and the new substrates where the silicon layer is bonded on a buried distributed Bragg reflector (DBR). Quality factors of the in-plane resonant modes are analyzed both experimentally and theoretically when the substrate structure is changing. It is shown that the underlying DBR can enhance the in-plane quality factors by a factor 2.5 by reducing the losses. The out-of-plane light extraction efficiency of the cavities and of defectless photonic crystals are also discussed.