All-optical diode based on asymmetric nonlinear optical absorption in ternary transition metal chalcogenides.

As the typical representative of ternary transition metal chalcogenides, CrPS₄ and MnPS₃ exhibit unique light-matter interactions, demonstrating great potential in photonic devices. In this work, we systematically studied the nonlinear optical (NLO) responses of CrPS₄ and MnPS₃ flakes by the I-scan technique. CrPS₄ and MnPS₃ flakes show saturable absorption and reverse saturation absorption excited by fs laser at wavelengths of 600 nm, respectively. Furthermore, utilizing the non-degenerate transient absorption technology, we observed that the fast and slow carrier relaxation times of CrPS₄ at different probe wavelengths were components with constants of about 1.4-3 ps and 490-1420 ps, respectively. Their excellent ultrafast NLO properties imply that they can be applied in photoelectronic fields for advanced and functional devices. Here, we designed and demonstrated an all-optical diode based on a CrPS₄/MnPS₃ tandem structure by breaking the time-reversal symmetry, and it achieved nonreciprocal transmission of light similar to that of a p-n electron diode.