Germanium-on-Silicon Waveguide Engineering for Third Harmonic Generation in the Mid-Infrared

In this paper, we propose the rigorous and sophisticated engineering of germanium-on-silicon waveguides for the efficient wavelength conversion from 10.60 to 3.53 mu m and from 6 to 2 mu m by means of third harmonic generation. In our investigation, the influence of waveguide fabrication tolerances, sidewall tilting angles, crystallographic axis orientation, laser wavelength drifts, and chromatic dispersion on the phase matching between the pump and harmonic optical modes, has been taken into account. Finally, conversion efficiencies as high as -35.68 and -23.46 dB have been achieved theoretically in optimized straight waveguides and resonant microcavities, respectively, with a pump wavelength of 10.60 mu m.