Silicon-loaded waveguide in sputter-deposited PZT-on-MgO platform for on-chip electro-optic applications

In this article, we propose and demonstrate a thin film-sputtered PZT as a base for the development of Si photonic devices such as waveguides, MZI, and electro-optic modulators. We report the optimization of PZT on MgO (002) substrate to obtain a highly oriented PZT film (100) with a surface roughness of 2 nm. Si gratings are simulated for TE mode with an efficiency of −2.2 dB/coupler. The enhancement in the simulated overlap coefficient of 200% is observed in Si-on-PZT compared to the conventional PZT-on-SOI architecture. The fabricated Si gratings on PZT show a coupling efficiency of −10 dB/coupler and a 1 dB bandwidth of 14 nm for a TE Gaussian source. The DC electro-optic characterization for MZI (Si-on-PZT) shows a spectrum shift of 71 pm/V in the C-band compared to 14 pm/V obtained for PZT-on-SOI. The enhancement of 400% in experimental response is attributed to the improved electro-optic overlap as well as PZT film quality. Our proposed design can potentially be used for programmable photonic integrated circuits using an electronically tunable PZT thin film as well as in neural networks.