| Unlike conventional lasers,random lasers do not have an optical resonator,and the optical feedback is mainly provided by multiple scattering in disordered medium.As a new type of laser,random laser has attracted the attention of more researchers due to its special luminescence principle and optical properties,and has important theoretical value and wide application prospects.Quantum dots exhibit excellent performance in the field of random lasers due to their quantum-limited threshold effect.Among them,CdSe/ZnS quantum dots,as typical quantum dots of type I core-shell structure,exhibit good optical properties and stability.Metal nanoparticles(NPs)because of its unique local surface plasma resonance(LSPR)action,can limit the electric field around the surface of NPs,the resulting strong local electric field can effectively improve the density of photons around the metal NPs,to achieve the purpose of enhancing the emission performance of the laser,in the preparation of low threshold,controllable nature of the random laser field has great application prospects.Based on the LSPR effect of metal NPs,the random laser properties of CdSe/ZnS quantum dots based on nanoparticles of different gold and silver alloys were studied.Compared with the CdSe/ZnS quantum dot samples without metal NPs,it is proved that the LSPR of metal NPs has an enhancement effect on random laser.By comparing the sample emission of different gold and silver alloy nanoparticles,it is found that when the initial gold and silver molar ratio is 1:1,the outgoing random laser of the sample has a relatively low threshold,about 1.22 m J/cm2,and according to the power Fourier transform analysis of the outlet spectrum of the structure,the equivalent cavity length of the random laser not the film thickness is obtained,indicating that the feedback in the system mainly comes from multiple scattering inside the medium.Through the analysis of the sample emission spectra of different gold and silver alloy nanoparticles,it is found that with the increase of the initial Au molar fraction,the plasma confanter of the metal nanoparticles continues to redshift,resulting in a random laser spectral center shift from about 626 nm to 633 nm.In this study,the random laser wavelength can be easily tuned by changing the initial gold-to-silver molar ratio of gold-silver alloy nanoparticles,which facilitates the realization of tunable lasers.The random laser radiation properties of Ag NPs-doped CdSe/ZnS quantum dots were investigated based on substrates with different surface microstructures,such as glass substrates and polydimethylsiloxane(PDMS)wrinkled substrates.Organic phase Ag NPs of different particle sizes were prepared by sodium borohydride reduction method,and it was found that as the particle size increased,the peak wavelength of the absorption spectrum gradually redshifted.Through the uninterrupted pumping of samples,it is proved that polymethylmethacrylate(PMMA),because of its own characteristics,can enhance the stability of CdSe/ZnS quantum dots emitting random lasers.By comparing the random laser emission characteristics of samples based on silver nanoparticles of different sizes,it is found that as the particle size of Ag NPs increases,the threshold of the system decreases.By comparing the random laser emission characteristics of samples with different substrate structures,it is found that the folded microstructure substrate is more conducive to random laser emission than the glass microstructure substrate.By comparing the emission spectra of Ag NPs with different concentrations,it is found that the laser emission intensity is higher when the concentration of Ag NPs is higher. |
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