Research On The Spectral Characteristics And Regulation Of Nanolasers Based On Micro-nanostructures

The optical microcavities made up of semiconductor micro/nano materials have attracted much attention in the field of light-material coupling due to their good limitation of light field.Micro/nano lasers composed of semiconductor materials have also been widely studied and applied in scientific research and industrial fields.As a kind of typical direct wide bandgap material,II-VI semiconductor materials have rich morphological characteristics ? lager exciton binding energy and strong oscillator strength,which makes them are perfect vectors to study the coupling between light and matter.Among them,cadmium sulfide(CdS)has significant applications in optoelectronic devices,such as nanometer laser and photodetectors.This thesis mainly studies the light-material coupling characteristics of Fabry-Pérot(F-P)microcavity composed of CdS nanoribbons and the single-mode lasing of CdS nanoribbons by constructing coupling cavities.The main contents of the thesis are as follows:1.The development background of F-P optical microcavity is elaborated.Based on the light-material coupling in semiconductor materials,exciton-polariton in semiconductor materials is reviewed.In the process of laser miniaturization,the monochromaticity of the lasing output becomes highly desirable because of less mode competition,better beam quality and higher stability,the realization method of single mode laser in semiconductor micro/nano laser is summarized.2.The CdS nanoribbons with flat surface and uniform thickness used in our experiments were grown by V-L-S mechanism.In order to improve the spatial resolution of spectral measuring for nanoribbons,we designed and built a spectrum measurement system,which can realize fluorescence spectrum and resolution spectrum.Among them,the system resulting in the spatial resolution in sub-microns,and get the dispersion relation of CdS nanoribbons by taking photographs at one-time.3.The CdS nanoribbons have shown great potentials for fabricate of functional nanoscale laser due to their excellent gain medium and bandgap engineering performance,which can form optical microcavities.In this work,a tunable coupling nanoribbon cavity was simply obtained by using home-made transfer platform.Based on this,the Vernier effect-driven high performed single-mode laser was realized.The laser mode can be reversibly tuned between single-mode and multi-mode by adjusting the gap of two coupling nanoribbons.The coupling constants and optical losses of different gaps were demonstrated by simulating,from which,near-field coupling effect dominated the laser's mode type was clarified.This work offered an alternative route towards realizing mode-tunable nanoscale lasers,which may have great potential in flexible multifunctional optoelectronic devices.4.The microcavity and lasing properties of single CdS nanoribbon are investigated.Utilized the home-made spectrum measurement system of micro-area based on microscope system,we demonstrate the dispersion relation of exciton-polariton in CdS nanoribbon.To dispersion relation of exciton-polariton we use the coupled oscillators model to produce a theoretical fitting to the angle-resolved mapping data,and revealing the vacuum Rabi splitting of polariton up to 181 me V,and the exciton-like and photon-like components in low polariton states at different cavity-exciton detuning.Furthermore,by combining Young's interference method,the parity of the lasing modes in the F-P cavity are directly observed in the angle-resolved spectroscopy,the applicability of Young's interference method in F-P type lasers is confirmed,which should also be useful to light-material coupling in semiconductor materials.5.A tunable “U”-shaped nanowire(NW)was simply obtained by using home-made transfer platform and elastic substrate,and the bandgap variation can be controlled reversibly,the fluorescence spectral properties and lasing modes of curved CdS NWs under strain modulation are also systematically investigated.Considering the strain-induced energy band variation and curved morphology of NW,we speculate that the strain-driven carrier's redistribution is the key role leading to the redshift.Furthermore,the simulation of the light field demonstrated the optical transmission properties of the buckled NW.Results indicated that strain-modulated CdS NWs would improve the adjustability of optoelectronic devices and may be essential for the design of reconfigurable opto-mechanical-devices.