Scattering loss of multi-slot silicon light emission device: Theory and experiment

Ever since slot waveguide was first proposed, its unique photon confinement characteristic has attracted a lot of interest. Its applications in several areas such as silicon light emission device, nonlinear optical device, and optical bio detection have been proposed and experimentally verified. Different merit functions for device design have also been proposed for some specific applications. This paper presents results from theoretical and experimental studies performed on horizontal multi-slot waveguides made of alternating nm-thick Si and SiO₂ layers. The surface roughness of an interface is mathematically described by two parameters: the RMS roughness and the correlation length. Using a statistical approach in solving Maxwell´s equation, the scattering loss of multi-slot waveguides for TE and TM polarization is calculated. A top-scattering method is used to experimentally measure the propagation loss of 2D planar waveguides, while light is coupled into the waveguide via a prism coupler. The experimental results agree well with our theoretical predictions. The optical gain for TM polarization in multi-slot waveguides, using realistic parameters, is also calculated. The result shows that optical gain is much higher than the additional scattering loss due to the multiple interfaces.