The Investigation Of Random Laser Based On SiO₂ Particle Scattering

There are three necessary conditions for conventional laser,which are pumping source?optical cavity?gain medium,respectively.Unlike the Fabry Perot?F-P?cavity,the cavity of a random laser is composed of scattering particles.The exiting light creates multiple scattering between the scattering particles,thus forming a complete closed loop.This loop is equivalent to the optical cavity in a conventional laser,and the multiple scattering gain enhances the excitation radiation.Random lasers have the advantages of good stability,small size,low cost and easy fabrication.It has broad application prospects in display,lighting,medical,detection,storage and information transmission.Silica nanoparticles?SiO₂ NPs?have a strong scattering effect on light waves,and the raw materials are easy to obtain and low in cost.Basing on the above reasons,this paper has done the following research:1.A wavelength tunable random laser with doped SiO₂ NPs.Rhodamine 6G?R6G?was selected as a fluorescent dye and dissolved in an ethanol solution to form a mixed solution having a concentration of 3 mg/ml.Then,the curing agent and the polydimethylsiloxane?PDMS?oligomer were mixed at a ratio of 10:1,coated on the surface of the flexible silica substrate,and cured to obtain a tunable random laser.Next,the electric field enhancement around SiO₂ NPs was simulated by COMSOL software.The results show that SiO₂ NPs can enhance the random laser output wavelength.The random laser is pumped by using 532 nm incident light to study the spectral characteristics of the random laser emitted by different energy densities.The center wavelength of the random laser output is about 566 nm,and the full width at half maximum is stable at 4-5 nm.The threshold is 1.6 mJ/cm².2.The tunability of the output wavelength is achieved by mechanical stretching of a flexible random laser doped with SiO₂ NPs.The flexible random laser was fixed on the translation stage,and the flexible silicone substrate was mechanically stretched with a tensile length of 14 mm.The output center wavelength of the random laser was shifted from 566 nm to 554 nm with a decrease in light intensity.When the mechanical force acting on the flexible random laser is removed,the center wavelength of the random laser is restored from 554 nm to 566 nm,which realizes the wavelength tunability of the flexible random laser.Next,the emission wavelength characteristics of flexible random lasers without SiO₂ NPs were compared.Firstly,a3.random laser sample without SiO₂ NPs was fabricated.From the spectral line characteristics,it was found that a random random laser without SiO₂ NPs could also exhibit random laser phenomenon at a wavelength of 562 nm.However,from the spectral line analysis,the threshold of the flexible random laser with SiO₂ NPs is significantly lower than that of the flexible random laser without SiO₂ NPs and the emission wavelength is blue shifted by 4 nm.4.Produce a thin film random laser containing F8BT.F8BT was dissolved in a xylene solvent to form a mixture having a concentration of 22.5 mg/ml.Next,a 20 ul mixture was dropped into water,and after the volatilization was completed,a film sample having an uneven thickness was formed on the water surface.Observing the surface microstructure of the film under an optical microscope,it was found that the structure has irregular gully-like strips,which is advantageous for enhancing the scattering of light waves.Under the excitation of strong pump light,a random laser appeared at the output line at 580 nm with a threshold of about 19.8 mJ/cm².In addition to making a random film of a drop film,a random film laser with a sandwich structure and a random film laser produced by a film unwinding method were fabricated by a spin coating process.The F8BT spin coating film and the uncoated film did not exhibit random laser phenomenon.It is found that high-energy-density pump light is easy to ablate the random laser of the film when it is applied to the surface of the film sample.Further studies have found that there is ablation when the pump energy density of the two thin-film random lasers reaches 21 mJ/cm² and 29.4mJ/cm²,respectively.