Back-end integration of multilayer photonics on silicon

We present vertically-stacked a-Si:H and AlN photonic circuits deposited on silicon using back-end CMOS technology. At 1550-nm telecom wavelengths, the a-Si:H (0.5-µm×0.22-µm) and AlN (1-µm×0.4-µm) channel waveguides are measured to have low propagation losses of ∼3.8 and ∼1.4 dB/cm, respectively. Various passive devices with high performance are demonstrated on these two photonic layers, including multimode interferences (MMI), waveguide ring resonators (WRR), and arrayed-waveguide gratings (AWG). Moreover, the thermo-optic coefficients (dn/dT) of a-Si:H and AlN are measured to be ∼2.60×10
⁻⁴
and ∼3.56×10
⁻⁵
K
⁻¹
, respectively.