Femtosecond Laser Spectroscopy Study Of CsPbBr₃ And Bi₂O₂Se

In recent years,semiconductor materials have become one of the hotspots in the fields of materials science and condensed matter physics,among which two-dimensional layered materials and perovskite materials show great application potential due to their unique structures and excellent optoelectronic properties.CsPbBr₃perovskite nanocrystals have high photoluminescence quantum yield,narrow emission spectrum,and high optical gain,and are widely used in light-emitting diodes,solar cells,and lasers..Currently,most reports focus on the low-threshold amplified spontaneous emission of CsPbBr₃nanocrystals,want to obtain the cost-effective,excellent performance,and low-threshold of CsPbBr₃nanocrystal-based Lasers are still challenging.Bi₂O₂Se two-dimensional materials have excellent properties such as high carrier mobility,strong environmental stability,and adjustable band gap,and are widely used in photodetectors,thermoelectric materials and other fields.The response speed of the detector and the lattice thermal conductivity of the thermoelectric device are closely related to the carrier dynamics of the material.At present,some scholars have carried out research on Bi₂O₂Se carrier dynamics,but the carrier relaxation process is less explained and needs further study.The laser performance of the CsPbBr₃ microsphere cavity was analyzed by photoluminescence spectroscopy.The experimental results show that the microsphere laser with low threshold,tunable spectrum and high stability（the laser intensity can be well maintained under the excitation of the microcavity for up to 3 hours）has been successfully prepared,and the laser mechanism is proved to be electron-hole plasma recombination,and the laser-enhanced mode of the whispering gallery is verified by combining the theoretical and photoluminescence spectral data.The spectral test of the CsPbBr₃microsphere cavity with different diameters shows that with the decrease of the diameter of the microsphere cavity,the laser mode gradually decreases,and finally a single-mode laser can be obtained.The carrier dynamics process of Bi₂O₂Se was analyzed by ultrafast spectroscopic system.The reflectivity data analysis showed that the relaxation channel disappeared at 30K,which may be the structural change caused by long-range Coulomb interaction,and explained the other two relaxation channels.The graph of Bi₂O₂Se reflectance peak signal and pump flux shows that the material has entered the nonlinear region when excited by the pump flux of 59.7μJ cm^-2.Finally,an explanation is given for the time-domain terahertz spectral intensity changes at 2.03 and 2.35 THz.