Ultrafast All-Optical Logic Gates in Quasi-2D Perovskites

Quasi-2D perovskites are widely used in solar cells, photodetectors, and light-emitting diodes (LEDs) due to their excellent optoelectronic properties and stability. However, much fewer all-optical devices are realized based on quasi-2D perovskites. Although perovskites have large nonlinear optical coefficients, the relaxation progress of excitons and carriers will slow down the response time and reduce the signal contrast of the all-optical devices. In this paper, the exciton dynamics are investigated under off-resonance excitation in quasi-2D perovskite PEA2(FAPbBr3)2PbBr4. The spin-selective optical Stark effect (OSE) is observed through circularly polarized transient absorption measurements, and a Stark shift of 3.3 meV is achieved under 1.11 eV excitation. The hot-biexciton cooling process induced by two-photon absorption is also observed. A spin-based XNOR gate is demonstrated with a response time of approximate to 180 fs, and the logical signal contrast is enhanced through the competition of the OSE and the hot-biexciton effect.