Two-Photon Excitation Enhanced High-Efficiency and Phase-Conjugate Stimulated Mie Scattering of Perovskite Nanocrystals Suspended in n-Hexane

Two-photon excitation enhanced backward stimulated Mie scattering (SMS) is generated in a system of perovskite (CsPbBrxI3-x) nanocrystals (NCs) of ?11 nm size suspended in n-hexane, when pumped with ?816 nm and ?10 ns laser pulses. The major linear absorbance band of these PCs is in the 550-300 nm spectral range; thereby, at the pump wavelength (?800 nm), a considerable two-photon excitation enhanced spatial redistribution of the PCs leads to the formation of an effective Bragg grating that ensures a lower pump threshold requirement and a higher energy transfer efficiency (?) from the pump pulse to the SMS output pulse. Under optimized experimental conditions, the measured efficiency in this system reaches a high value of ? = 40%. In addition, the output backward SMS beam exhibits a superior optical phase-conjugation property, and the temporal behavior of SMS output has also verified the proposed theoretical model.