Germanium-on-SOI waveguides for mid-infrared wavelengths

We report on the development of Germanium-on-SOI waveguides for mid-infrared wavelengths. The strip waveguides have been formed in 0.85 and 2 μm thick Ge grown on SOI substrate with 220 nm thick Si overlayer. The propagation loss for various waveguide widths has been measured using the Fabry-Perot method with temperature tuning. The minimum loss of ~8 dB/cm has been achieved for 0.85 μm thick Ge core using 3.682 μm laser excitation. The transparency of these waveguides has been measured up to at least 3.82 μm.