Second-order nonlinear optical processes enable a wide range of applications used in research and industry. The majority of available second-order nonlinear devices however relies on bulk nonlinear crystals with low second-order nonlinearity. By exploiting the advancements made in integrated optics, materials with large second-order nonlinearity can enable efficient and small-sized on-chip nonlinear devices at low cost. Unfortunately, silicon and silicon nitride, mostly used for photonics integrated circuits exhibit negligible second-order nonlinearity (χ(2)) and alternate materials have to be investigated. Lead zirconate titanate (PZT) thin films with high second-order nonlinearity stand as a good candidate for on-chip nonlinearity. An electric-field induced tuning of χ(2) is demonstrated here in PZT thin films grown on glass substrates with a tuning efficiency of 3.35 pm V−2. Strong second-harmonic generation is recorded and a very high dominant tensor component 𝜒(2)𝑧𝑧𝑧 of 128 pm V−1 is reported. The χ(2) of the PZT thin films can be reversed by poling with a DC electric field at room temperature. This opens avenues for highly efficient and tunable on-chip nonlinear devices.
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