Large, Electric-Field Induced Tunable and Reversible χ(2) in PZT Thin Films for on-chip second-order nonlinearities

Second-order nonlinear optical processes enable a wide range of applications e.g., laser sources, optical parametric oscillators, electro-optics modulators. Most devices exploiting these second-order effects however rely on bulky nonlinear crystals and are expensive. The heterogenous integration of nonlinear thin films on silicon (Si) or silicon nitride (SiN) have been pursued to mitigate the issue of a vanishing χ (2) in these platforms for small and power efficient nonlinear devices. Strongly nonlinear thin films of Lead Zirconate Titanate (PZT) have been successfully integrated on SiN [1] and Si [2] waveguides for high speed and low-loss electro-optic modulators. We demonstrate here strong second harmonic generation (SHG) from PZT thin films.