High Performance 7 $\times$ 8 Ge-on-Si Arrayed Waveguide Gratings for the Midinfrared

Ge-on-Si low-loss waveguides and 7 × 8 arrayed waveguide gratings (AWGs) are presented for operation near 4.7 μm wavelength. Propagation loss in the range of 3 dB/cm for fully etched waveguides and 1 dB/cm for shallow-etched waveguides is reported. 200 GHz AWGs in a 7 × 8 configuration with various waveguide aperture widths and etch depths are designed and characterized. For fully etched AWGs, the insertion loss values as low as -2.34 and 3 dB mean cross talk of -29.63 dB are achieved. The shallow-etched AWG has an insertion loss of -1.52 dB and crosstalk of -28 dB.