Very Compact Metal Slab Waveguide Reflectors as Integrated High Reflectivity Mirrors on High Index Contrast Waveguides

Metal slab waveguide reflectors integrated with very compact high index contrast waveguides are described, designed and simulated. Reflection and transmission characteristics of such reflectors are studied using 2-D and 3-D finite different time domain (FDTD) simulations. It is shown that the reflection and transmission coefficients can be controlled by adjusting the gap and length of metals of the reflector. Reflection coefficients much higher than cleaved facets and even higher than metal coated facets are possible. Reflection coefficients of almost 97% are achievable using only 1 μm long reflectors. The sensitivity of obtained reflection as a function of alignment errors indicates that more than 90% reflectivity is possible with 0.1 μm alignment tolerance. It is also shown that very compact Fabry-Perot resonators with FSR of 67.1 nm are possible using such reflectors. These resonators are directly coupled to input and output waveguides and have 5 μ m active length and less than 7 μm overall length including mirrors.