Fabrication of polarity inverted LiNbO3/GaN channel waveguide by surface activated bonding for high-efficiency transverse quasi-phase-matched wavelength conversion

GaN is an attractive material for integrating optical quantum devices. Adding a large optical nonlinearity of MgO doped congruent LiNbO3 (MgO:CLN) to GaN will improve the efficiency of quantum light sources. In this work, we proposed transverse quasi-phase-matched wavelength conversion devices with waveguide core materials of MgO:CLN and GaN. The waveguide core is formed by an adhesion-free surface activated bonding (SAB). A high thin film transfer yield was achieved with a high bonding strength of 4 MPa by optimizing the bonding conditions and reducing the surface roughness of the GaN film to be 0.5 nm in a 100 × 100 μm2 area using chemical mechanical polishing. The MgO:CLN/GaN waveguide structure was successfully fabricated by MgO:CLN thin film transfer, lift-off and dry etching processes. This MgO:CLN/GaN adhesion-free SAB technique is expected to be applied to various devices, such as optical devices and electronic devices, to enhance their functionality.