Effective four-wave mixing in the lithium niobate on insulator microdisk by cascading quadratic processes

Whispering-gallery-mode resonators can dramatically enhance the light-matter interaction, benefitting nonlinear optics in many ways. Here, we demonstrate effective four-wave mixing (FWM) in a lithium niobate on insulator (LNOI) microdisk via cascaded quadratic nonlinear processes of second-harmonic generation and difference-frequency generation (i.e., cSHG/DFG) in the telecommunication band. The effective FWM process can be used as an optical parametric amplifier and can mimic an effectively strong Kerr nonlinearity. This shows the great promise of an integrated LNOI platform for nonlinear frequency conversion.