Directional Emission Of The Electromagnetic Field By Metal Nanoparticles

Metal nanoparticles are widely used in the fields of electromagnetic fields and radiation enhancement.In this paper,the enhancement of electromagnetic field,radiation rate and radiation direction of metal nanoparticles were studied.In view of metal nanostructures,the mechanism of radiation enhancement is theoretically studied.In this dissertation,the enhancement effect of metal nanostructures on radiation point sources is studied.Then,the polymethyl methacrylate(PMMA)layer was placed between gold nanoparticles and gold substrate.The effects of different amounts,configurations and sizes of gold nanoparticles on the total radiation rate,far-field radiation rate and radiation direction of the radiation sources,such as molecular or quantum dot,in the PMMA layer were studied.The results show that the total radiation rate and far-field radiation rate increase with the increase of the number of gold nanoparticles,and when the radius of gold nanoparticles satisfies the local plasmon resonance condition,the peak of total radiation rate and far-field radiation rate will appear.When the distance between gold nanoparticles is a certain value,unilateral radiation or central radiation can be achieved,and all the light can be collected without a high numerical aperture objective.By measuring the far-field radiation pattern,the change of the number,layout and size of nanoparticles can be inversely deduced,thus realizing the high-precision sensing of the number,layout and size of nanoparticles.Experimentally,the method of defocusing is used to qualitatively verify the directivity of the radiation direction of metal nanoparticles.In theory,the quasi normal mode(QNM)is used to prove that the fluorescence and scattered light have the same emission direction.The research results have guiding significance for fluorescence molecular sensing and spontaneous radiation enhancement.