Second harmonic and sum frequency generation in silicon nitride microring on thin-film lithium niobate

We demonstrate significant second harmonic generation (SHG) and sum frequency generation (SFG) on a thin-film lithium niobate (TFLN) platform by loading a silicon nitride (SiN) microring resonator, which avoids the dry etching of lithium niobate. By optimizing SiN-loaded TFLN waveguide geometry, the phase-matching conditions between the fundamental pump laser and the SHG/SFG signals are designed. Combining with enhancement by the microring resonator, remarkable SHG and SFG signals with conversion efficiencies of 16.43%/W and 5.90%/W are realized, respectively. Compared to traditional TFLN photonic platform, this CMOS-compatible strategy offers an opportunity for achieving large-scale on-chip nonlinear photonic devices based on TFLN.