The Effect On Laser Emissions For Localized Surface Plasmon Resonances Generated With Noble Metallic Nanoparticles

Laser has very important application value in the field of optical nonlinear effects,sensing,communication and other fields.When the device is reduced to micronano size,how to lower the laser threshold is an important research content to better achieve the above applications.The local surface plasmon resonance of the noble metal nanoparticles can form strong coupling with the external light field,and the local field intensity can be greatly enhanced on the surface of the structure.This allows for the formation of a coupling of the gain material such as fluorescent molecular with the noble metal nanoparticle,which enables greater fluorescence emission through the surface enhancement effect.Therefore,the hybrid structure composed of noble metal nanoparticles and fluorescent molecules is expected as a super fluorescent molecule to enhance the gain strength of the gain medium,thereby effectively reducing the laser threshold and increasing the laser output intensity.In order to verify this scheme,this paper takes silver nanospheres and Aucore Ag-shell nanorods as examples.By adjusting the nanoparticle size and shell thickness,the modulation of the local surface plasmon resonance wavelength was achieved,and then adjusted the gain characteristics of the gain medium composed of rhodamine 6G fluorescent molecules.The laser output characteristics of the resonant cavity formed by the cuvette were tested experimentally.By analyzing the laser output characteristics of the rhodamine6 G solution doped with different concentrations of noble metal nanoparticles,an noble metal nanostructure and size that optimized laser threshold reduction were obtained.These experimental results show that in addition to enhancing the fluorescence emission characteristics,the precious metal nanoparticles themselves have a certain absorption loss,so it is necessary to adjust the concentration and structure of the nanoparticles to obtain a smaller laser threshold.The specific work is as follows:1.We used chemical synthesis methods to prepare silver nanospheres with diameters of about 32 nm,56 nm,66 nm,82 nm and 98 nm.At the same time,we prepared gold nanorods with length and diameter of about 55 nm and 17 nm,respectively,and then the silver shells with thicknesses of about 1.0 nm,3.5 nm,7.0 nm,8.5 nm,10.0 nm,and 12.0 nm were coated on them,respectively.These precious metal nanoparticles have different localized surface plasmon resonance peak positions,which can achieve different enhancement effects on the fluorescence emission of rhodamine 6G.2.Using a cuvette as an optical resonant cavity(the cavity length is about1 cm)and using a pulsed laser as the pumping source,and the same diameter silver nanospheres with different concentrations were mixed with 1 mM rhodamine 6G as the gain medium for laser detection experiment.The measurement results show that compared with the undoped rhodamine 6G solution(the threshold is about 6.98 ?J),the laser threshold decreases first and then increases with the increase of silver nanosphere concentration,so the threshold of laser output can be reduced by adding silver nanoparticles.When the diameter of silver nanospheres is about 32,56,66,82,98 nm,the corresponding minimum threshold of laser is about 5.78,5.12,4.84,5.03 and5.68 ?J,respectively.3.Under the same experimental conditions,the gain medium was replaced by gold core silver shell nanorods with different thicknesses and Rhodamine 6Gmixed solution to examine the effect of different noble metal nanostructures on the laser output characteristics.The experimental results show that compared with the undoped rhodamine 6G solution,gold core silver shell nanorods can also effectively reduce the laser emission threshold,and with the increase of the concentration of gold core silver shell nanorods,the threshold also appears the phenomenon that decreases first and then increases.when the thickness of silver shell is about 1.0,3.5,7.0,8.5,10.0 and 12.0 nm,the minimum laser threshold is about 5.36,5.30,5.34,5.14,5.13,and 5.20 ?J,respectively.From the above experimental results,it can be seen that although the local surface plasmon resonance of the noble metal nanoparticles has a certain absorption loss,the threshold of the laser output can still be effectively reduced by using the surface enhanced fluorescence effect,and the threshold can be reduced to about 70% compared to undoped conditions when the suitable noble metal nanostructures are selected.This result has important reference value for the production of low threshold micronano laser.At the same time,by adjusting the nanostructure of precious metals,it is expected to further improve the output performance of laser.