Two-photon-pumped amplified spontaneous emission from Ruddlesden-Popper perovskite flakes

Herein, we report the two-photon pumped amplified spontaneous emission (ASE) in the 2D RPPs flakes at room temperature. We prepared high-quality (BA) 2 (MA) n-1 Pb n I 3n+1 (n = 1, 2, 3, 4, 5) flakes by mechanical exfoliating from the fabricated crystals. We show that the (BA) 2 (MA) n-1 Pb n I 3n+1 flakes display a tunable two-photon pumped emission from 527 nm to 680 nm, as n increases from 1 to 5. Furthermore, we demonstrated two-photon pumped ASE from the (BA) 2 (MA) n-1 Pb n I 3n+1 (n = 3, 4, 5) flakes. The two-photon pumped ASE thresholds of the RPPs are lower than lots of the other semiconductor nanostructures, indicating an excellent performance of the RPPs for two-photon pumped emission. In addition, we investigated the pump-wavelength-dependent two-photon pumped ASE behaviors of the RPPs flakes, which suggest that the near-infrared laser in a wide wavelength range can be converted into visible light by the frequency upconversion process in RPPs. This work has opened new avenues for realizing nonlinearly pumped ASE based on the RPPs, which shows great potential for the applications in wavelength-tunable frequency upconversion.