The Emission Regulation Of Dye Random Laser Based On Novel Carbon Materials

Random laser has potential applications in the areas of biosensing,micro-illumination,and optical imaging due to its characteristic of no resonant cavity,low spatial coherence and small feature size.To adjust the lasing properties,various materials are employed in random laser systems including metal nanomaterials,semiconductors,perovskites,and biological tissues.Metal nanoparticles have become important materials in random lasers because of surface plasmon resonance effect.Due to novel optical properties and good chemical stability,carbon materials are expected to become good candidates to adjust the lasing properties.The study of how to adjust the lasing properties of metal nanoparticles and carbon materials takes on great significance and application value.In this thesis,we analyze the effects of Au nanoparticles,Au/graphene composites,and silicon carbide(SiC)nanowires as scattering medium on random laser emission properties,including threshold,emission intensity,and center wavelength.We aim to achieve a random laser with controllable properties.The main contents and conclusions in this thesis are shown as follows:(1)Lasing properties of Au/graphene composite structures in a random laser system are studied.The Au/graphene composites with stable structure and properties are obtained by chemical reduction and adsorption.The effect of Au/graphene composite on random laser threshold and emission intensity is investigated,and it is confirmed that the addition of graphene is beneficial to optimize the random laser performance.Compared with the sample containing Au nanoparticles,the emission intensity with Au/graphene composites increases by 45.0 %,and the random laser threshold decreases by 34.8 %.The results indicate that the addition of graphene can make the transmission peak of the composite material closer to the photoluminescence of the dye,which promotes the laser emission intensity and decreases the threshold.By inserting graphene,the mean free path of photon scattering decreases,which enhances the photon gain effect and improves the laser performance.Au nanoparticles and graphene cooperate to increase the intensity of random laser emission and lower the threshold.It could provide a convenient and effective method for realizing low energy consumption and high feedback random laser.(2)SiC nanowires are employed in random laser systems as the scattering medium.The different concentrations of SiC nanowires on the properties of random laser are studied.The results indicate that the SiC nanowire concentration influences the emission intensity,threshold and central wavelength of the random laser.As the concentration of SiC nanowires in the sample increases from 0.02 mg/m L to 1.00mg/m L,the random laser emission intensity increases and the threshold value decreases to about 20 μJ/pulse.With a further increase in the concentration of SiC nanowires,the threshold of the random laser increases and the emission intensity decreases.It is because as increasing the SiC nanowires concentration,the mean free path of photon scattering decreases,the scattering frequency of the photon is increased,thus,more optical gain is obtained for the photons which promote the excitation efficiency to obtain lower laser threshold and higher emission intensity.However,when the concentration of SiC nanowires is too large,the photon scattering frequency further increases resulting in self-absorption of fluorescence radiation emerging.Furthermore,the lasing wavelength can be adjusted by tuning the SiC nanowires concentrations,reaching 14 nm.The random laser enhanced by SiC nanowires is stable and pumped repeatable.This study provides a convenient and effective method to optimize the performance of random laser for new semiconductor materials,which provides a technical way to realize the low threshold,high performance,and tunable wavelength random laser.(3)The flexible dye-doped random laser with high stability is produced using SiC nanowires as the scattering medium.To investigate and compare the random laser properties under various bending and stretchingconditions,the laser emission data are statistically evaluated and analyzed.The flexible laser property presents excellent optical stability in wavelength,emission intensity,and peak width by bending and stretching ranging from 0 % to 30 %.The laser samples can withstand at least 200 cycles of bending tests and 30 minutes of nonstop pumping excitation,confirming the system’s high repeatability and optical stability.A scattering density variation model is employed to explain the emission stability and system characterization.SiC nanowires have a high specific surface area and aspect ratio,thus,there is nearly no change in the scattering medium density.Under system bending and stretching,the mean free path of photons is not altered,resulting in the stable emission property of the flexible random laser.