Light Emission and Slot Waveguide Effect in Er-doped SiO2/Si nanocrystalline Multilayer Structures

In this thesis, Er doped SiO2/nc-Si multilayer structure a promising material for on-chip silicon light emission devices, is studied in detail. It is demonstrated, for the first time, that infrared Er emission could be enhanced by an Er doped SiO2/nc-Si multilayer structure. It is also determined that energy transfer from nc-Si to nearby Er ions, is responsible for this emission enhancement. The SiO2/nc-Si multilayer structure also works as a horizontal multi-slot waveguide, in which a high percentage of photons are strongly confined in the nanometer thin SiO2 layers, where the refractive index is lower than its surrounding environments. Owing to this unique photon distribution, we theoretically predicted and experimentally demonstrated that free carrier absorption (FCA) could be strongly suppressed. Our observation of free carrier suppression in this structure is the first experimental demonstration of this effect in a slot waveguide. Scattering loss from multiple interfaces in this device is the price needed to be paid for this benefit. To see if the costs outweigh the benefits, we proposed a model to theoretically calculate the scattering loss. Experimental measurements of the loss, using a top scattering method, agree well with the simulation results. Based on Er emission enhancement, the FCA suppression and the scattering loss due to interfaces, a detailed parametric study suggested that overall optical gain at 1535 nm could be achieved under certain conditions. The last piece of our experiment is an ultrafast pump probe study of our device. The obtained results confirmed our