| Thin film organic lasers(TFOLs)exhibit great advantages,different from inorganic materials,in communication signal propagation,biochemical sensing,optical storage and other applications due to their ease of processing,chemical versatility,wavelength tunability and low cost,which have attracted extensive research from scientists.Among them,compared with conventional lasers,random lasers have been deeply studied since the 1990 s because of their unique properties of coherence in disordered systems.The laser emission principle of organic thin film random lasers is divided into two categories: classical random laser and quantum random laser.In classical random laser theory,the space size of the film disordered cavity is much larger than the emission wavelength,which constitutes a long-range disordered system.When the system is large enough,there may be unstable periodic closed light propagation path,which makes the emitted light coherent.In quantum random laser theory,the scattering medium in the film constitutes short range disorder,and the "Anderson" localization occurs by using light scattering to form a closed loop,thus realizing the emission of coherent laser.Based on the above random laser theory,two kinds of film-type random lasers are designed in this paper,and the laser properties of the films are controlled by morphology tuning.The specific research work of the thesis is as follows:1.A new POSS and fluorine-containing randomised polymer(PMPF)was synthesized by polymerization of free radical solution with methyl methacrylate(MMA),trifluoroethyl(TFEMA),and methacrylate POSS(MAPOSS)as raw materials.The chemical structure of PMPF was characterized by proton nuclear magnetic resonance spectroscopy and infrared spectrometer.X-ray diffraction patterns(XRD)and atomic force microscopy(AFM)were used to characterize aggregation behavior and the formation of fluorinated chain segment microphase structures in copolymer films.The optical signal gain is realized by doping laser dye PM597,and the long-range fluctuation of refractive index caused by the microphase structure in the copolymer as the scatterer and the rough surface of films is used to produce coherence,resulting in random laser emission.2.N,N'-di-(1-hexylheptyl)perylene-3,4,9,10-tetracarboxylic bisimide(PBI-HH)was synthesized for organic laser dye.PBI-HH doped polystyrene(PS)or polymethylmethacrylate(PMMA)thin films coated by spraying method were prepared.The influence of spray film forming parameters,polymer-dye molecular interaction and annealing process on the luminescent properties of the thin films was discussed.dye molecular aggregation states were controled based on the concentration dependence of PBI by discussing the optical properties of PBI-HH/PS thin films.The dye molecular aggregation states that are more susceptible to stimulated emission were picked,and random lasing emission was realized by using the morphology characteristics of thin films.In addition,the tunable organic thin film random lasers were prepared by changing the spraying parameters to control thin film morphology.The effect of spraying parameters,polymer-dye molecular interaction and annealing process on the luminescent properties of films was discussed by using fluorescence spectrophotometer to measure fluorescence spectra of samples.Concentration-dependent regulation of dye molecular aggregation states.The stimulated emission properties of films with different aggregation states are characterized by Nd:YAG laser pumped samples,spectrometer received emission signals.The luminescent properties of films are discussed to verify that the single molecule is more susceptible to stimulated emission of dye molecules aggregation state.The mechanism of spray film formation was analyzed by optical microscope and grayscale analysis,and the effects of annealing and spraying solvent on the film morphology were characterized.Tunable organic film random laser was prepared by changing the spraying parameters to realize the regulation of film morphology. |
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