Fabrication of a bonded LNOI waveguide structure on Si substrate using ultra-precision cutting

The heterogeneous integration of an LNOI waveguide device on a mature Si platform is interesting for the creation of a future high density and multi-functional platform. This paper reports the fabrication of a bent LNOI waveguide on Si substrate using surface activated bonding with a Si nanoadhesive layer and post-bond ultra-precision cutting at room temperature. This bonding method demonstrates the sufficient bond strength between an LN wafer and thermally grown SiO₂ to withstand ductile-mode cutting for waveguide fabrication. In this work, the width, height, and bent radius of the ridged LNOI waveguide on Si substrate were approximately 5, 2.5, and 300 μm, respectively. These room-temperature bonding and cutting methods are expected to fabricate various heterogenous devices with a large coefficient of thermal expansion mismatch between dissimilar materials, not just LNOI/Si waveguide devices.