Fluorescence Intensity Improvement Of Phosphor By Using Micrometer Or Namometer Scale Structure

With the rapid development of the micro/nano photonics,micro/nano photonic structures were designed and has been used in medical,communications,energy and so on.The enhancement of fluorescence intensity is an important aspect of the application of micro/nano photonic structures.LED is the core of lighting and display devices.Along with the development of quantum dot fabrication technology,quantum dot LED was prepared and it has more advantages than the existed white LED in producing white light.So it is of great significance to study the fluorescence of quantum dots.At the same time,it is important to improve the sensitivity of fluorescence detection in the field of life science.Due to the small size of micro/nano structure,electromagnetic and energy density are mainly concentrated in the micro/nano structure near the surface.However,in the medical application,especially for the measurement of cells in vitro,the fluorescence collection of the sample is far away from the structure.Therefore,it is necessary to enhance the far field fluorescence of fluorescent material in the far field region of the structure.Based on the above analysis,in order to improve the emission of quantum dots and apply it to the white LED,the author designed a periodic multilayer heterostructure,by using RCWA and FDTD,the influence of the number of period,the thickness of each layer and the incident angle on the reflection has been confirmed.And the electric field distributions of several specific wavelengths are also obtained.A number of high reflection bands are obtained,corresponding to UV,violet,blue,cyan and red,respectively.Besides,the high reflection bands are adjustable.The experimental results show that fluorescence intensity of quantum dots is enhanced by using the proposed structure.So the theoretical and experimental results are presented that the structure can realize the fluorescence enhancement of quantum dots.The enhancement mechanism is the interference from the multiple reflection and incidence in the structure.In order to improve the fluorescent material in the far field of the structure,we designed a half-cylindrical Au groove,and comparing with other structures.In the process of excitation,the time domain and frequency domain at the same point(Point A)is measured when the light is TE/TM polarization.From the time domain graph,each structure better than bare glass;frequency domain shows that the excitation light at 980 nm(excitation wavelength of UCNPs),proposed structure has largest E2.During the emission process,UCNPs is placed at the same position(Point A),and the fluorescence intensity of the far field is measured.At the wavelength of 617 nm,the electric field distributions of several typical structures are obtained and the electric field distribution of half-cylindrical Au groove when the UCNPs are been placed at different positions are also obtained.Besides,we studied the far field fluorescence intensity of fluorescent material at different points of the structure.The results show that the structure can improve the emission by 8.25 times when the UCNP is 4.4 μm away from the bottom of the groove compared with the bare glass.Due to scattering,constructive interference and coupling of optical modes in the sample region,the emission of UCNP enhanced.A novel microcavity structure is designed,the substrate uses Si and SiO2,and two Ag reflectors are placed horizontally.The fluorescence enhancement effect was convinced by comparing with the other three structures in the process of fluorescence emission.Through the analysis of the electric field at the wavelength of 656 nm,we can know that the coupling mode of fluorescent substance in the structure is stronger.