Inversion symmetry broken 2D SnP2S6 with strong nonlinear optical response

Nowadays, realizing miniaturized nonlinear optical (NLO) device is crucial to meet the growing needs in on-chip nanophotonics as well as compact integrated devices. The strong optical nonlinearities, ultrafast photoexcitation dynamics, available exciton effects as well as without lattice matching make two-dimensional (2D) layered materials potential candidates for integrated and nano-scale NLO devices. Herein, a novel and inversion symmetry broken 2D layered SnP2S6 with strong second-harmonic and third-harmonic response has been reported for the first time. The second-order susceptibility (χ(2)) of SnP2S6 flakes can reach up to 4.06 × 10−9 m·V−1 under 810 nm excitation wavelength, which is around 1–2 orders of magnitude higher than that of most reported 2D materials. In addition, the NLO response of 2D SnP2S6 can break through the limitation of odd/even layers and exhibit broadband spectral response. Moreover, since the second-harmonic signal is closely related to structure variation, the second-harmonic response in 2D SnP2S6 is extremely sensitive to polarization angle and temperature, which is beneficial to some specific applications. The excellent NLO response in 2D SnP2S6 provides a new arena for realizing miniaturized NLO devices in the future.