Dispersion of the third-order optical nonlinearities in 2D (PEA)₂PbI₄ perovskite film

We report the wavelength-dependent third-order optical nonlinearity of two-dimensional halide organic-inorganic perovskite (PEA)₂PbI₄ film experimentally. The high-quality two-dimensional (PEA)₂PbI₄ film prepared via confinement-assisted drop-casting process exhibits ultrafast optical response and large third-order optical nonlinearities, and the measured nonlinear refractive index is closer to the quantum perturbation model accounting for the excitonic effect. In addition, the wavelength-dependent optical response transition from self-focusing to self-defocusing, saturable absorption to reverse saturable absorption has been observed and investigated. The experimental results confirm the large third-order optical nonlinearities in (PEA)₂PbI₄ film and may make inroads toward developing cost-effective high-performance optoelectronic devices.