Perovskite Based Micro/nano Laser And Its Modulation

Development trend of modern information technology are miniaturization of device,low power consumption and high operation speed.Semiconductor lasers play an important role in practical application and scientific research.In recent years,great progress has been made in the miniaturization of semiconductor lasers,However,up to now,the micro/nano laser devices still face the problems such as large optical loss,high laser threshold,low optical coupling efficiency and so on.In order to realize the application level of micro/nano lasers,the research on finding new semiconductor materials with high gain and low loss and more reasonable cavity design has been carried out.In the last few years,researches about lead halide perovskite semiconductors have become a hot spot in the field of photovoltaic devices.In the visible spectrum range,lead halide perovskite can be used as an ideal laser gain material.Research on the preparation of micro/nano laser based on lead halide perovskite has made great progress.However,there is still much room for improvement in the research of perovskite micro/nano laser.In this paper,the optical properties of gain media,the optimal design of device cavity,the physical mechanism of laser,and the time-domain controlling are studied to further improve the performance of perovskite micro/nano laser.(1)From the perspective view of gain materials,considering the exciton effect is not obvious in bulk lead halide perovskite,and at the same time,bulk lead halide perovskite lack of mechanical flexibility,which limited the integrating with other optical platforms,this paper first introduces two experimental methods of preparing perovskite nanosheets,e.g.solution method and chemical vapor deposition method.For few-layer perovskite synthesized by solution method.It is found the absorption and photoluminescence spectra blue-shifted compared with bulk perovskite,and the blue shift is closely related to the number of layers of the material,which confirmed the quantum effect and dielectric effect.Besides,for the third harmonic generation in the material,it is found that the peak value of the third harmonic signal generated near the absorption band edge,and the third harmonic signal blue-shifted under femtosecond pumping,which confirmed the exciton effects can influence the third harmonic generation process.On the other hand,perovskite nanosheets synthesized by CVD method is relatively thick,but its transverse dimension can reach several hundred micrometers and has good mechanical flexibility.For hexagonal flakes,it is found that stable WGM mode lasing can be formed,which exhibited its potential as gain media in micro-lasers.(2)From the point view of cavity design,considering the mechanical flexibility of perovskite nanosheets synthesized by CVD method,integrating them w ith functional silicon nitride substrate prepared by electron beam lith ograph and plasma etching can archive functional lasing emission.In the experiment,the mechanism of using the shape of cavity structure to precisely control the perovskite lasing behavior is demonstrated.Different shapes of perovskite/silicon nitride heterost ructure lasers are obtained without damaging the photoelectric properties of perovskite materials.The resonator of the laser is determined by the shape of the silicon nitride substrate,while the perovskite nanosheet can provide the optical gain.Furtherm ore,the functions of perovskite laser,such as wavelength tuning,mode number control,direction emission,laser array emission,and lasing interaction in the coupled cavity,are realized in the experiments,which shows the potential of the hybrid structure of perovskite nanosheet and silicon nitride micro-disk as on-chip light source.(3)As a scheme that can break optical diffraction limit,the surface plasmon laser is expected to play an important role in integrated optics.In this paper,the hybrid mode surface plasmonic nano-laser based on lead halide perovskite is studied.The perovskite/Si O2/Au is fabricated in the experiment.The hybrid plasmonic nano-laser is verified by thickness measurement,optical polarization and transient time response measurement.Then,controlling the resonance mode of a hybrid plasmonic laser by the shape of metal substrate is demonstrated.In the designed configuration,perovskite is used as gain medium,and the shape of metal substrate determines the resonant mode.Furthermore,the substrate is designed as a periodic array structure,and the hybrid mode surface plasmon laser array can be obtained.After the preparation of the samples,the anion ratio of the prepared perovskite can be changed by chemical vapor deposition,and the emission wavelength can also be accurately controlled.(4)In the last section,the concept of bound state in continuum is used to control the perovskite lasing emission in time-domain.In the experiment,perovskite thin film is used to fabricate a photonic crystal slab,and it is proved that the designed structure can produce single-mode laser based on symmetry protected BIC.Then,using the characteristics of destructive interference of BIC,a new degree,the imaginary part of refractive index,is introduced to change the perovskite photonic crystal slab by controlling the spatial pumping configuration where two pumping beams overlap partly.The asymmetric distribution of the imaginary part of the refractive index in the slab results in the change of the far-field polarization characteristics of the BIC laser.The far-field pattern of the laser is directly modulated to realize optical switching,and the switching time can be reduced to 1.5 ps.This mechanism is applicable to different semiconductor material,so it has a wide application.