Vertical integration of KTN on SOI wafer

Optical modulators play an important role in communication systems, and silicon has been a focal point in this field thanks to its compatibility with CMOS fabrication. However, silicon's lack of inherent electro-optic behavior makes it suboptimal for modulation purposes. Conversely, potassium tantalate niobate (KTN) materials boast an improved electro-optic coefficient, presenting a path for improving modulation efficiency. However, limited research exists on KTN materials due to the difficulties associated with their fabrication. Here, a fabrication methodology is described for wafer-scale vertical integration of KTN material onto silicon-on-insulator (SOI) wafers. The resulting devices exhibit a propagation loss of 3.3 dBmm¹ and a transition loss within the range of 0.46 to 0.76 dB, which are in agreement with simulations. This method tackles the fabrication challenges and showcases the potential of utilising KTN as the integration material on silicon platform for future optical modulators.