Reversible and Tunable Second-Order Nonlinear Optical Susceptibility in PZT Thin Films for Integrated Optics

Abstract

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 (chi((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 chi((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 chi zzz(2) of 128 pm V-1 is reported. The chi((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.