Propagation Loss Improvement in Ge-on-SOI Mid-Infrared Waveguides Using Rapid Thermal Annealing

We report on the improvement of propagation loss in Ge-on-SOI waveguides developed for mid-infrared wavelengths. Strip waveguides of varying widths have been developed in 0.85 μm thick Ge core and an improvement of up to ~3.5 dB/cm has been achieved by annealing the samples at 700 °C for 120 s. The improvement is consistent for both TE and TM polarized light at 3.682 μm. The method is proven feasible for repairing material growth defects and achieving loss performance commensurate with that required for integrated photonics for sensing applications. The minimum propagation loss achieved is ~10 dB/cm after annealing.