The Regulation And Mechanism Of Photoluminescence Based On Metal Halide Perovskites Single Crystal

Metal halide perovskites have achieved excellent light-emission performance due to their halogen atom-dependent tunable bandgap,strong exciton effect,high quantum efficiency,long carrier lifetime,high absorption coefficient,and narrow emission linewidth.These excellent photoelectric properties make them one of the most promising photoelectric device materials.At the same time,the design of micro-nano optical cavities based on bound states in the continuum,parity-time symmetry,surface plasmons,and optical topological insulators has received extensive attention.These designs break through the limitations of traditional optics.When the size of micro-nano optical cavities is further reduced,they can not only maintain optical resonance modes with high-quality factors but also realize optical detection,photon transmission,and optical switches based on emission regulation.These designs have promoted the further development of on-chip integrated photonic circuits and micro-nano photonics.Thus,it is essential to integrate metal halide perovskite materials with high optical gain coefficients and novel micro-nano optical cavities exhibiting low leakage losses to ultimately achieve a high-performance micro-nano light source design with tunable emission modes.Currently,most of the research on metal halide perovskites is still focused on the synthesis of the materials themselves and the characterization of their photoluminescence behavior.However,there has been relatively little research into laser device design,optoelectronic modulation,and the underlying emission modulation mechanisms.This has made it difficult for perovskite microlaser to achieve widespread commercial applications in the field of optoelectronic devices.To address this gap,this dissertation aims to primarily study metal halide perovskite materials and their structural design in conjunction with new micro-nano optical cavities.This approach will be utilized to achieve emission regulation of perovskite laser and fluorescence,reduce the energy threshold of perovskite luminescence,develop specific applications of perovskite laser,explore possible new physical mechanisms of perovskite laser,and investigate and summarize future development directions of high-performance micro-nano light sources based on metal halide perovskite.This dissertation focuses on four main areas of research,and conclusions are presented in the following sections.(1)Investigation on fiber lasers based on perovskite nanocrystals.In this work,a perovskite fiber laser with adjustable modes,a low energy threshold,and axial pumping was constructed by combining perovskite nanocrystals with micro-nano fibers.The fiber laser comprises high-quality perovskite nanocrystals spin-coated on the surface of the micro-nano fiber,and the related laser performance characterization results demonstrate its exceptional laser performance.Firstly,the fiber laser can be tuned from single-mode(D≥15 μm)to multimode(D≥30 μm)by modifying the diameter of the micro-nano fiber.Secondly,high optical gain coefficient and well crystallized CsPbBr3 perovskite nanocrystals act as the gain medium,and the high arc and smooth surface of the micro-nano fiber diminishes light leakage loss(Q≈2300),resulting in the laser energy threshold as low as 11.25 μJ/cm2,and can be operated continuously for 200 minutes(1.2×107 pulses);Thirdly,polymethyl methacrylate is used to coat the surface of the device,making the perovskite fiber laser operable underwater,and it can be stored for a long-term(≥30 days)at room temperature(T=24℃,RH=40%).Lastly,due to the intrinsic waveguide mode of the micro-nano fiber,the fiber laser exhibits high polarization state emission(R=0.85)and long-distance transmission(L≥10 cm).The design of the perovskite fiber laser in this work is simple,has a low manufacturing cost,and provides excellent optical performance.It is expected to have widespread use in active fiber-based laser light sources,signal processing,fiber sensing,and other devices.(2)Investigation on emission regulation and mechanism of optical cavity laser based on parity-time symmetry.In this work,based on the symmetrical distribution of the complex refractive index of the structure in space and the evanescent wave coupling between the rectangular waveguide and the circular micro-nano optical cavity,our work presents a system for regulating laser emission through dual micro-nano optical cavities.We employed theoretical derivation and numerical simulation to prove that the unidirectional and single-mode laser emission in the dual-micro-nano-cavity waveguide system originates from the combination of parity-time(PT)symmetry and strong chirality of the system.Asymmetric coupling between opposite traveling wave components in the rectangular waveguide and the optical cavities on both sides enabled us to achieve the strong chiral emission of the system(α=0.93),which was not affected by the shape of the optical cavity(circular,quadrupole,snail shell linear)or mode order restrictions(l=1,2,3).The design can thus be extended to other types of optical cavities.Under the effect of PT symmetry breaking,the system can achieve unidirectional and single mode laser emission with an extinction ratio lower than-20 dB(50 nm<h<380 nm and 200 nm<d<550 nm),which greatly reduces the structure accuracy required to obtain chirality in the preparation of optical cavity systems.In particular,we were able to achieve selective unidirectional laser emission with an extinction ratio of-52 dB by weakening the CW2 mode component.Furthermore,we extended the system to detect nanoparticles accurately,detecting nanometer particles with radius ranging from 5 to 50 nm by comparing the emission extinction ratio of different ports.Our work on the dual micro-nano-cavity waveguide system can provide potential applications in optical switches,optical interconnects,and light detection based on the principle of regulated laser emission,promoting the role of micro-nano-cavities in integrated photonic circuits.(3)Investigation on emission regulation and mechanism of perovskite nanosheets laser based on plasmons.This work is based on the metal/dielectric layer/semiconductor composite structure,and the perovskite nanosheet plasmon laser is regulated at room temperature.The composite structure was obtained by growing single-crystal CsPbBr3 nanosheets with high crystal quality on the surface of the Ag/SiO2 substrate by chemical vapor deposition(CVD).First of all,through experiments and calculations,this work confirms that the optimal dielectric layer thickness of the composite structure is 10 nm,and the laser energy threshold of perovskite nanosheets under this thickness is the lowest(50.35 μJ/cm2)with the highest quality factor of Q≈2000;Secondly,this work,through a comprehensive comparison with photon-mode perovskite nanosheet lasers,proves that when the size of the nanosheets gradually shrinks(L≤5 μm),the plasmons in the nanosheets(β=0.18)shows more advantages than photon mode(β=0.03)laser;thirdly,this work modulates the perovskite nanosheet plasmon laser mode by changing the pump energy,in specific structural parameters(L=5.6 μm,H=0.3 μm,g=10 nm)perovskite nanosheets achieve real-time mode conversion from singlemode(44.07 μJ/cm2)to multi-mode(96.32 μJ/cm2).Finally,this work studies the laser gain mechanism of perovskite nanosheets in this composite structure,and proves that the laser gain of perovskite nanosheets in this structure comes from the electron-hole plasma.This work opens up new avenues for optimizing and studying the performance and mechanism of perovskite plasmonic lasers and is of great significance for applications in on-chip photonic devices,sensors,data storage,and high-resolution imaging.(4)Investigation on emission regulation and mechanism of perovskite quantum dots fluorescence based on metasurface.In this work,based on the Mie resonance of nanostructures,a silicon-based all-dielectric metasurface was designed to regulate the emission of Mn:CsPb(Cl/Br)3 perovskite quantum dots.The metasurface is a nanocomposite structure composed of coaxial rings and cylinders.First of all,through the combination of theoretical calculation and modeling simulation,this work proves that the Mie resonance comes from the electric ring dipole G,and the Fano resonance comes from the mode interference between the magnetic ring dipole T and the electric dipole P,Among them,the dipole mode interference reduces the leakage loss of the structure,generates a highly localized electromagnetic field,(|E|/|E0|)Max=76,(|H|/|H0|)Max=48.2,and greatly improves the resonance quality factor(Q≈1300);Secondly,this work expounds the physical mechanism of quantum dot fluorescence regulation through theoretical derivation,and the Mie and Fano resonance modes of the metasurface are simultaneously used to improve the excitation efficiency(|Γ-exc/Γexc0|≈120),intrinsic emission efficiency(|QYem/QYemo|≈1.79)and far-field emission efficiency(|ηext/ηexto|≈1.57).Corresponding code programs were written to calculate the expected effect of luminescence regulation(|Iexc,em,ext/Iexc,em,ext0|≈335);Finally,this work prepared the designed metasurface by using micro-nanofabrication structure,and the actual effect of the metasurface on the fluorescence regulation of perovskite quantum dots was verified by experiments.The final experimental results showed that the perovskite quantum dots in the metasurface achieved about 17.3 times luminescence enhancement.This work designs and prepares a new type of dense metasurface array,which can provide a high-value localized electromagnetic field,which is of great significance for future research on nonlinear fluorescence-based biological detection and quantum light source regulation.