Foundry-compatible thin film lithium niobate modulator with RF electrodes buried inside the silicon oxide layer of the SOI wafer.

Ever-increasing complexity of communication systems demands the co-integration of electronics and photonics. But there are still some challenges associated with the integration of thin film lithium niobate (TFLN) electro-optic modulators with the standard and well-established silicon photonics. Current TFLN platforms are mostly not compatible with the silicon photonics foundry process due to the choice of substrate or complicated fabrication requirements, including silicon substrate removal and formation of radio-frequency (RF) electrodes on the top of the TFLN. Here, we report on a platform where all the optical and RF waveguiding structures are fabricated first, and then the TFLN is bonded on top of the silicon photonic chip as the only additional step. Hence, the need for substrate removal is eliminated, and except for the last step of TFLN bonding, its fabrication process is silicon foundry compatible and much more straightforward compared to other fabrication methods.