Fluorescence Manipulating And Imaging Base On Metal-Dielectric Composite Structure

Fluorescent labeling and detection technology has long been one of the most widely used technology in the field of bioscience due to its high sensitivity.In recent years,a variety of super-resolution fluorescence imaging methods,such as Stimulated emission depletion technology,Photo activated localization microscopy,maximize the application of fluorescent technology in super-resolution imaging.In order to obtain stronger fluorescent signals,a variety of functional fluorescent photonic devices have been designed to improve the excitation and collection efficiency of fluorescence,which include optical antenna structure and multi-layer functional substrate.Most of these photonic devices make use of the interactions between fluorophores and the near-field optical mode of the structure to control the emission parameters of the fluorophore,including the radiation direction,intensity,polarization,wavelength and so on.In this paper,we mainly study the new phenomena appeared in the combination of multi-layer functional substrate,especially metal-dielectric waveguide with confocal scanning imaging system and leakage radiation microscopy,these new phenomenon include high efficiency confocal fluorescence imaging and the generating of nondiffracting fluorescence Bessel beam.And the propose of two new fluorescence detection methods based on the two sets of imaging systems,which are quasi-near-field confocal fluorescence detection and out-of-focus fluoresce imaging in leakage radiation microscopy.These studies are of great significance for the use of functional fluorescent photonic devices for fluoresnce imaging and fluorescent beam shaping,and provide new ideas and means for the design and characterization of new novel functional fluorescent photonic devices.The main research works and conclusions are as following:1.The polarization dependence of the excitation of waveguide modes(WMs)on metal-dielectric waveguide(MDW)is investigated experimentally,a prism is used to couple the cylindrically symmetric vector beams(CVBs)which is generated through a liquid crystal polarization converter(LCPC)to excite the WMs.The LCPC could change the generated CVBs from radially polarized beam to azimuthally polarized beam gradually by changing its working voltage,thus dynamically control the distribution of WMs on the structure.The interference pattern of two opposite transmitted WMs were recorded by photoresist thus enable the measurement of MWs propagating parameter directly.To evaluate the possibility of using MDW as confocal imaging substrate,we theoretically studied the focusing property of WMs and found that the focus of transverse magnetic modes(TMs)perform smaller focal spot than transverse electric modes(TEs).By help of back focal plane imaging method,we selectively excited and focused the TM.The focused field was then used in the scanning imaging process and high efficient fluorescence images were obtained.2.Experimentally studied the confocal method in the characterization of quasi-near field fluorescence coupled emission just below the MDWs.In the experiment,two sets of MDWs were designed,the first set is of thin dielectric layer which support surface plasmon polaritons(SPPs);the second set is of thick dielectric layer which support multi WMs.Through confocal scanning imaging process,field distribution images at micron distances below the MDW were measured.These field images indicate that along with high angle precision,confocal method could present directly transmitted fluorescence emission from the fluorophores located out of the coupling region of MDW and the modes overlapping in quasi-near filed area which could not be present by far field measurement such as back focal plane imaging.These phenomena were verified by the theoretical field distribution acquired by FDTD method.This near field measurement makes up the shortfall of far field measurement and offers new method for the design and characterization of new fluorescence photonic device.3.We proposed the concept of defocus image with leakage radiation microscopy(LRM).The defocus here include defocus of objective and defocus of detector.The defocus of objective here means by moving away of objective to the fluorescence coupled structure,the field distribution of fluorescence emission just below the structrue were imaged.In the experiment,we measured the objective defocus image of fluorescence emission from the most commonly used glass substrate and four different fluorescence coupled device(SPPs substrate,multi-modes MDW,one dimensional photonic crystal and Tamm substrate).The defocus of detector means the movement of imaging sensor between the front focal plane image and back focal plane image to record the fluorescence signals,which connects the spatial distribution of the sample with its corresponding Fourier information.By this connection,we accomplished the measurement of different dielectric film thickness in parallel with nanometer accuracy.4.By taking the similarity of the wave vector distribution of surface plasmon coupled emission(SPCE)and that of Bessel beams,we successfully generated fluorescence Bessel beam based on the conversion field of SPCE by LRM 4f imaging system.The generated beam was first order Bessel beam initially and could be convert to zeroth order Bessel beam with smaller central lobe by insert a spiral phase plate into the optical path.Because every single fluorescence emitter could form an independent Bessel beam,the proposed method here could generate multiple Bessel beams at the same time.Highlights of the dissertation are as following:1.New MDW structure was used as an imaging substrate successfully in confocal scanning imaging system,on which fluorescence image intensity three times stronger than SPP substrate was accomplished.By selectively excite and focus the TM mode in MDW substrate,the resolution of the confocal imaging system is maintained while the high coupling efficiency fluorescent image is obtained.Additionally,the MDW with thick dielectric film here could avoid the quenching effect of metal thus enable longer effective fluorescent lifetime.2.The concept of defocused fluorescent imaging based on LRM was proposed for the first time.The defocused images could reflect the fluorescence field in the micron distance below the structure.Among them,detector defocused images could form connections between the spatial distribution on front focal plane and the Fourier information on back focal plane of the imaging system,thus enable parallel measurement of optical parameter of the structure,like the film thickness,refractive index and so on.Here,taking film thickness for example,we show the accurate parallel measurement of four dielectric layers with 10nm thickness difference.3.The commonly regarded incoherent fluorescence beam was shaped to no diffracting Bessel beam and remain no diffracting propagation property for over 100 millimeter.This work indicate the possibility of using photonic device to reshaping fluorescence beams.It is of potential application in super-resolution fluorescence imaging,fluorescence sensing and so on.