Research On Surface Electromagnetic Field Of Multilayered Structure In Subwavelength Scale

As the development of nano optics,it is expected that the new design of the structure will realize unprecedented regulation of the electric wave and exhibit various novel properties.The advent of new electromagnetism concept sunch as surface plasmon polaritons,optical antennas,metamaterial,metasurface and photonic crystal leads people to use various electromagnetic surface modes to realize the manipulation of light,thus,design relevant functional devices.This paper focuses on the multilayered structure under subwavelength scale and mainly studies the characteristics of surface electromagnetic field in it,designing related microstructure to realize the manipulation of light.The main research works and conclusions are as following:1.We propose an imaging measurement device and method based on metal film SPR(Surface Plasmon Resonance)dispersion on the basis of Kretschmann attenuated total reflection structure.The imaging measurement device is characterized in that a continuous spectrum white light source is adopted,so that the measurement range of a spectrum is enlarged;in addition,by the utilization of lens focusing and optical grating light splitting,angles and wavelengths are split in the space in an orthorhombic mode.The light intensity is detected through a CCD,an SPR reflection spectrum of all the wavelengths and angles can be obtained at a time,then a whole color dispersion curve is obtained at a time,angle or wavelength scanning is not needed,signal obtaining speed is greatly increased,and spectrum sampling precision is greatly improved.And the imaging measurement of the complex refractive index of metal film in wide spectrum is realized by use of the imaging measurement device.Rapid and non-scanning imagination measurement within the wide spectrum range is achieved.2.We introduce a method to replace a multilayered structure by a bulk material:effect medium theory and present a comprehensive analysis of the effective medium approximation(EMA)breakdown in deeply subwavelength all-dielectric multilayer made of alternating layers by means of transfer matrix method.We demonstrated that the approximation will be invalid at the vicinity of the effective medium's critical angle for total internal reflection and obtained an analytical criterion for the breakdown of EMA,which depends on the layer thickness,incident angle and the permittivity difference between alternate layers.We rebuilt EMA by adding higher order correction onto the traditional effective permittivity.Furthermore,we found the EMA breakdown arisen from the boundary effect cannot be repaired in the traditional homogenization strategy with only one layer of effective medium.By adding an artificial matched layer after the conventional effective layer,the boundary effect breakdown was neatly removed.3.A surface structure is introduced on the basis of multilayered structure:concentric rings.We design the Bloch surface wave(BSW)Lens and study the focusing effect of it by interaction between vector beams and chiral structures.Compared to SPP,BSW has larger wave vector and tinier losses,which means the focal points will be more concentrated and powerful.We analyze the chirality of the structure and demonstrate that a concentric ring slot is the optimum structure to obtain a focusing spot under circularly polarized illumination.Subsequently,we discuss the construction of the structure,indicating that to receive high-efficiency focusing field,the number of stack pairs should be less than five,and the period of the grating should be adjusted on account of the different wavelength inside the slot.Furthermore,we verify that the intensity of focusing field has a limitation with the increasing cylinder number.Highlights of the dissertation are as following:1.We propose an imaging measurement device and method based on metal film SPR(Surface Plasmon Resonance).The dispersion curves of different wavelengths are represented in the same dispersion image by means of imaging.Then a whole color dispersion curve is obtained at a time.Angle or wavelength scanning is not needed.Signal obtaining speed is greatly increased,and spectrum sampling precision is greatly improved.Rapid and non-scanning imagination measurement within the wide spectrum range is achieved.And the imaging measurement of the complex refractive index of metal film in wide spectrum is realized by use of the imaging measurement device.2.We present a comprehensive analysis of the effective medium theory(EMT)breakdown in deeply subwavelength all-dielectric multilayer made of alternating layers by means of transfer matrix method.We give the dispersion relation of the EMT according to the reflectivity of the multilayered structure.We demonstrated that the approximation will be invalid at the vicinity of the effective medium's critical angle for total internal reflection and obtained an analytical criterion for the breakdown of EMA,which depends on the layer thickness,incident angle and the permittivity difference between alternate layers.We rebuilt EMA by adding higher order correction onto the traditional effective permittivity.Furthermore,we found the EMA breakdown arisen from the boundary effect cannot be repaired in the traditional homogenization strategy with only one layer of effective medium.By adding an artificial matched layer after the conventional effective layer,the boundary effect breakdown was neatly removed.3.We propose that Bloch wave vector for finite photonic structure approaches to that of semi-infinite photonic structure gradually as the number of stack pairs increases.We analyze the focal pattern considering the interaction between the spiral ring structure and light with specific spin and orbital angular momentum and point that concentric ring is the optimized structure to realize the efficient focusing of BSW Lens.The geometric parameters of concentric ring BSW lens are optimized to obtain most intense focal field in the consideration of tradeoff between increasing ring number and reflective loss of ring slot.