Low Loss Germanium-on-Silicon waveguides for integrated Mid-infrared Photonics

Low loss Ge-on-Si waveguides are demonstrated in the 8 - 14 mu m atmospheric transmission window, a technology that will enable detection and sensing of unique molecular vibrations. Such a low cost platform would have applications in key markets such as pollution monitoring, explosives detection and point of care diagnostics. Rib-waveguides are fabricated using electron beam lithography and dry etching. The waveguides propagation losses are characterized using the Fabry-Perot technique, and are found to be below 5 dB/cm across the measurement range of 7.5 to 11 mu m wavelength, reaching as low as similar to 1 dB/cm. The contribution to the losses are analyzed using the experimentally measured Si substrate losses, and the calculated scattering losses from an analytical model. The results verify the feasibility of the Ge-on-Si platform for integrated mid-infrared photonics and sensing.