Study On The Superfluorescence Effect Of Perovskite Quantum Dot Ensemble

Perovskite quantum dots have excellent optical and electrical properties,such as ultra-high luminous efficiency,large oscillator strength,tunable emission wavelength in visible light range,and excellent charge transport properties,so they have great application potential in the fields of illumination,display,laser and solar cells.When large numbers of quantum dots self-assemble into a superlattice structure,it is convenient to form a system that gathers a large number of boson in a small area.Under the effect of virtual photon exchange,phase synchronization the internal dipoles will happen,thus causing the collective effect of mutual cooperation.The synchronously emitted fluorescence is called superfluorescence.As a transient coherent optical effect,the photoluminescence(PL)intensity of superfluorescence is proportional to the square of the dipole density and its radiation lifetime is inversely proportional to the density.Putting this identical particle ensemble in an optical cavity will form the so-called cavity enhanced superfluorescence which has excellent optical properties.This work separately compares the spectral characteristics and radiation dynamics of the single quantum dot,the quantum dot superlattice and the quantum dot superlattice microcavity samples in detail.Due to the coupling effect,the radiative peak position in the spectrum has a obvious red shift,its width become obviously narrower,from the order of 10 meV to several meV or below and its radiation lifetime is reduced from nanoseconds to picoseconds.We then carefully study the dependence of the maximum radiation intensity and radiation lifetime of the fluorescence on the pumping laser power base on quantum dot superlattice and quantum dot superlattice microcavity samples.For the quantum dot superlattice microcavity samples,when the pumping power has not reached the threshold,the maximum fluorescence intensity and radiation lifetime is consistent with the law of quantum dot superlattice samples.When the pumping power exceeds the threshold,the PL intensity will be greatly increased and the radiation lifetime will be greatly reduced.In addition,this paper discusses the coherence and polarization characteristics of the emitted PL from the two materials.It is found that the coherence time increases from sub-picosecond to picosecond,even could during the entire radiation time.The radiation form is changed from the nonpolarized of ordinary superfluorescence to the linear polarization of cavity-enhanced superfluorescence whose degree of polarization is up to 90%.In order to manipulate the quantum state in the perovskite quantum dot superlattice,we introduced the other excitation pulse as the control light during the superfluorescence process.The collision between the new dipole group excited by the second pulse and the dipole group formed by the first excitation pulse will inevitably cause the destruction of the original quantum state,so the original coherent quantum state will be transformed into a disordered classic state.This behavior in material will not only cause a change in fluorescence intensity,but also induce a change an the fluorescence coherence.The destruction and reorganization of quantum states provide ideas to control the macroscopic coherent of the material component.The control mechanism in the perovskite microstructure is expected to apply in ultrafast quantum simulators and miniature coherent light sources.