Preparation And Optical Gain Of Perovskite Micro/Nanomaterials

Traditional semiconductor lasers have high output power,high controllability,and high focusing ability,which can be applied in cutting,welding,laser processing,and other fields.However,the manufacturing process of traditional semiconductor lasers is complex and involves the preparation and assembly of multiple materials,resulting in high manufacturing costs.For example,although single crystal lasers have low defect density,their compatibility limitations affect the application of traditional semiconductor lasers in certain specific fields.Therefore,exploring semiconductor materials of different dimensions and morphologies is an important way to solve the problems of traditional semiconductor lasers.In recent years,perovskite materials have emerged as a class of semiconductor materials with excellent optoelectronic properties.Their wide bandgap,broad absorption spectrum,high luminescence efficiency,and high carrier mobility make them highly attractive in the field of optoelectronics.Furthermore,the band structure and optical properties of perovskite materials can be tuned through chemical synthesis and physical structure design to further optimize device performance.Therefore,perovskite materials have been widely used in micro-nano optoelectronic devices.However,the preparation process of perovskite lasers is still complex,and the device structure is relatively large,limiting their application in micro-nano lasers.In this thesis,we focus on adjusting the preparation method and using water to induce phase transformation and generate heterostructure in0D Cs₄Pb Br₆ perovskite through component stripping and recombination,and we successfully prepared a nanoporous bilayer heterojunction laser.We also improved the method to prepare ultra-thin quasi-2D perovskite NMABr-FAPb Br₃ thin films with better device compatibility than perovskite single crystals.By combining them with metamaterial HMM,we fabricated surface plasmon resonance laser and achieved sub-wavelength laser emission,thereby realizing the miniaturization of perovskite lasers.Additionally,we combined the ultra-thin quasi-2D perovskite NMABr-FAPb Br₃thin film with a distributed feedback cavity to achieve low-threshold single-mode laser emission.Some recent research results related to perovskite are as follows:（1）We report the development of a new class of optically active porous media-porous perovskite heterostructures-that hold potential for limiting light transmission by means of diffusion or localization,combined with optical gain to create coherent light sources.These heterostructures are chemically composed of a 2D network of Cs Pb₂Br₅ and a 3D network of Cs Pb Br₃,obtained through direct water stimulation of a0D network of Cs₄Pb Br₆.Optical imaging shows that the light path formed by the low whispering gallery mode in the Cs₄Pb Br₆ resonant cavity provides optical feedback for amplifying light by strong scattering.Conversely,the structural heterogeneity suppresses the low whispering gallery modes in the porous heterostructure,restricting light mainly to the pumping region due to light scattering.Despite poor microcavity clarity due to local disorder,the porous heterostructure exhibits a pumping threshold that is only one-third to one-fifth of that of Cs₄Pb Br₆,comparable to that reported for Cs Pb Br₃.Analysis of feature modes by eigenvalue modeling reveals that the porous perovskite heterostructures support high-quality feature modes.These results demonstrate that perovskite heterostructures with interconnected porous scaffolds are a promising complex nanophotonic system for fundamental research and potential applications.（2）Due to its unique natural quantum well structure,quasi-2D perovskites exhibit excellent optoelectronic properties.The properties of quasi-2D perovskites can be tuned by selecting different organic cations.Here,we improved the preparation method and synthesized ultra-thin NMABr-FAPb Br₃ films（N2F8）with a thickness of only～10nm,as confirmed by FIB and TEM measurements.We studied the optical properties of the quasi-2D perovskite films and combined them with hyperbolic metamaterials（HMMs）to achieve subwavelength laser emission via surface plasmon resonance under external pump light.The ultra-thin quasi-2D perovskite surface plasmon laser provides a new method and idea for preparing micro-nano lasers.（3）Based on the quasi-2D perovskite NMABr-FAPb Br₃ film（N2F8）prepared in the previous work,we utilized the unique properties of ultra-thin quasi-2D perovskite to enable single-mode laser emission.However,as with any laser,the optical resonant cavity in the laser is also highly demanding,and the ultra-thin quasi-2D perovskite film cannot provide enough optical gain for photon feedback.Therefore,to achieve laser emission from the quasi-2D perovskite film,we set the structural parameters of a DFB cavity based on the excitation wavelength of the quasi-2D perovskite film and coated the film on the DFB cavity to prepare a DFB laser.This enabled low-threshold and excellent single-mode laser emission.