Understanding the Sidewall Dependence of Loss for Ge-on-Si Waveguides in the Mid-Infrared

Measurements of sidewall roughness by atomic force microscopy has been used to understand the waveguides losses of Ge-on-Si mid-infrared rib waveguides. Simulations indicate the measured roughness is well below values corresponding to the measured losses indicating sidewall roughness scattering is not the dominant loss mechanism.