Second-harmonic and cascaded third-harmonic generation in generalized quasiperiodic poled lithium niobate waveguides

Lithium niobate (LN) thin film has recently emerged as an important platform for nonlinear optical investigations for its large chi(2) nonlinear coefficients and ability of light local-ization. In this Letter, we report the first, to the best of our knowledge, fabrication of LN-on-insulator ridge waveguides with generalized quasiperiodic poled superlattices using the electric field polarization technique and microfabrication techniques. Benefiting from the abundant reciprocal vec-tors, we observed efficient second-harmonic and cascaded third-harmonic signals in the same device, with normal-ized conversion efficiency of 1735% W-1 cm-2 and 0.41% W-2 cm-4, respectively. This work opens a new direction for nonlinear integrated photonics based on LN thin film. (c) 2023 Optica Publishing Group

Automated summary

This Letter reports the fabrication of lithium niobate-on-insulator ridge waveguides with generalized quasiperiodic poled superlattices using electric field polarization technique and microfabrication techniques. The efficient second-harmonic and cascaded third-harmonic signals were observed in the same device, with normalized conversion efficiency of 1735% W-1 cm-2 and 0.41% W-2 cm-4, respectively. This work opens a new direction for nonlinear integrated photonics based on lithium niobate thin film.